Hot water supply troubleshooting - no hot water:

This article explains how to diagnose the sudden or loss of hot water pressure, quantity, or flow in a building or at specific plumbing fixtures.

We explain the difference between slowing or poor hot water supply and a hot water supply that suddenly is not there at all, and we give a diagnostic procedure to find and fix the trouble.

Page top illustration: a tankless coil and tempering valve installed on a hydronic heating boiler, used with permission, courtesy of Carson Dunlop Associates, a Toronto home inspection, education, and report writing tool firm.

How to Diagnose Sudden Loss of Hot Water Pressure & Flow in a Building

Have you lost all or some hot water pressure at some or all plumbing fixtures in your building?

Before you start fixing or buying stuff to fix a hot water problem, hot water problems and diagnostic guides for all kinds of hot water troubles are summarized

at WATER HEATER PROBLEM DIAGNOSIS.

You might want to check there to be sure you're fixing the right problem. Those questions & suggestions can help point you to the shortest route to troubleshooting hot water complaints like "no hot water" or "not enough hot water".

Article Contents

• DIAGNOSE NO HOT WATER AT ALL
• DIAGNOSE WEAK HOT WATER PRESSURE (FLOW) at SOME or ALL FIXTURES
• HOT WATER SYSTEM BLOCKAGE or CLOG POINTS to CHECK
• WATER VALVE TYPES - a gate valve may seem to operate but could be totally "off"
• WATER HEATER DRAIN-OUT - flush to remove debris causing blockage

...

Things to check if there is NO Hot Water Whatsoever

First, we outline things to check if you have no hot water at all. Second, we describe things to check if you have hot water but the pressure or flow rate is drastically reduced or just too darned weak.

We discuss the following:

• Possible places where hot water supply piping may be clogged
• Hot water valve clogging troubles
• Three types of plumbing valves used on water piping: Globe valve, Gate valve, Ball valve compared
• Draining the hot water heater tank to fix poor hot water pressure?
• Clues pointing to mineral debris clogging in hot water piping

Step 1: Check the building water supply

Does cold water flow at all fixtures? If so, then the building water supply is working.

Is there cold flow at hot water faucets?

If you have good water flow ("pressure") at hot water faucets, but it's cold,

then the water supply piping is not blocked and the problem is in the water heater itself, or in a mixing valve or the water heater is plumbed backwards.

If you have weak or no hot water flow at hot water faucets,

then the water heater's cold water inlet

or

hot water outlet (or dip tube) is blocked, perhaps with sediment, scale, or a closed valve or some other source of debris in the water piping system feeding the water heater or downstream from the water heater itself.

Check first for closed water supply valves, then, if you have good cold water flow but no hot water flow into or out of the water heater, check for a blockage in the water supply piping.

Step 2: Check the Incoming Cold Water Supply

Is there cold water flowing into the water heater?

Do you have cold water pressure?

Is the cold water inlet valve at your water heater open?

Is the water heater connected propery: the water heater outlet marked COLD must be connected to the cold water inlet piping and the water heater outlet marked HOT must be connected to the building hot water supply piping. l

Step 3: Check the Water Heater Energy Source

Check that the water heater has fuel

(oil or gas) or if it's electric, that it has electrical power. Has an LP fuel tank or oil storage tank run out? Has a filter clogged? Is a fuel valve closed?

Has a safety device turned off the water heater?

If yours is a gas fired water heater and IF the heater uses a temperature-operated automatic gas shutoff valve, that safety device could have shut down your system.

Details about the installation, testing, and functions of gas automatic shutoffs are

at GAS WATER HEATER AUTOMATIC SHUTOFF

Is the water heater turned on?

If your water heater is a tankless, demand type such as a Navien tankless water heater, it's possible that for some models hot water flow will stop completely if the water heater is turned off or needs to be re-set.

Step 4: Check that the Water Heater Burner or Heat Source Operates

Now we can move along into approaches to "no hot water" for each type of water heating system - for which water heater, calorifier, geyser, and hot water cylinder are all synonyms.

Water heater manuals:

Before we start: do you have the installation and operation or owner's manual for your water heater? Usually there is a nice troubleshooting table near the back of each heater manual.

If you don't have the instructions for your water heater, you can still follow the advice given in more -detailed articles at InspectApedia.com but you might want also to

see WATER HEATER MANUALS to find your equipment guide.

Here are the places to start troubleshooting for each type of hot water system that you might have in your building:

No Hot Water from an Electric Water Heater

See ELECTRIC WATER HEATER REPAIR GUIDE where we discuss checking for power, checking the thermostat, the reset button, the temperature control, and then we move on to describing how to test electric water heater elements and controls.

If you don't know how to even find the controls on an electric water heating system

see WATER HEATER TEMPERATURE TOO COLD or TOO HOT

No Hot Water from a Gas Fired Water Heater

Is there fuel in your LP gas tank? Or if your system uses piped-in natural gas, is the gas valve open?

Then see GAS BURNER FLAME & NOISE DEFECTS

Also see WATER HEATER LEAK REPAIR since water leaks can shut down a gas burner or its pilot

Then see GAS FIRED WATER HEATERS

No Hot Water from an Oil Fired Water Heaters:

Is there oil in the oil tank? If yes, then see OIL BURNER WONT RUN

Then see OIL FIRED WATER HEATERS

No Hot Water from an Indirect Water Heater

An indirect water heater is one whose hot water tank is heated by a physically separate heating boiler.

So first confirm that the heating boiler will turn on in a response to a call for heat in your building. If that works, then the problem is probably with the circulator or control that sends boiler water through the heating coil inside the indirect water heater.

See INDIRECT FIRED WATER HEATERS for details.

No Hot Water from a Solar Water Heater

Most solar water heating systems use an electric, gas, or oil backup system, so you may have two systems to diagnose.

Check that there is water in your system and that the necessary pumps are operating.

See SOLAR HOT WATER HEATERS for more about these systems

No Hot Water from a Tankless or Instant Water Heater

Tankless or On Demand or "Instant" water heaters may be electric, gas, or possibly even oil-fired devices that do not store any volume of hot water.

When you turn on hot water at the tap, water flowing through the system activates a control to turn on the heater that in turn heats water as it passes through the device.

So if you have no hot water, then your heater is either out of fuel or is not turning on. But these devices can be tricky: you need a fast-enough water flow through the heater to activate it. So running the hot water very slowly or very weak building water pressure could be the problem.

See TANKLESS WATER HEATERS

...

Things to Check if there is Weak Hot Water Pressure at One, Some, or All Fixtures

Question about diagnosing the cause of sudden loss of hot water pressure:

We suddenly lost hot water pressure [only] in the whole house, a week ago (7 years old townhouse: basement, main floor and upper floor). We drained the hot water tank, checked the various valves in the house but still same weak pressure.

Do you think it could be mineral deposits in the pipes? Or a clogged pipe? What is the most common cause for it? My plumber doesn’t seem to find out the cause of the sudden lost of Hot Water Pressure in the whole house.

Are there specialized plumbers for this situation? I assume not all plumbers have the training. I am kind of confused. - R. S.

Answer: things to check if hot water pressure is poor

We assume you mean that hot water pressure and flow are suddenly badly diminished in a building, not that pressure or flow have stopped entirely.

We also note that you refer to a hot water system that uses a tank, not a tankless coil to produce the building's hot water. Tankless coil clogging is discussed separately

at CLOGGED PIPES / TANKLESS COIL DE-SCALE.

If mineral clogging of the building plumbing system is a problem, usually we notice that hot water pressure is worse than cold water pressure, but also that the hot water pressure declines over time, rather than appearing to suddenly diminish severely.

So our diagnosis here is going to look for things that might produce a sudden severe reduction in hot water pressure - some sort of blockage or valve problem in the building water piping.

If hot water pressure suddenly stops entirely but cold water flow continues just fine, then a control valve may have been left closed, or a valve may have failed internally (appearing to be turned on but actually "off" internally due to a broken valve stem part), or a valve or pipe elbow may have become partly blocked by a chunk of mineral scale or by other debris. Here are some hot water pressure diagnosis suggestions:

Often the problem with loss of both hot and cold water pressure at plumbing fixtures is local clogging at a fixture such as faucet strainer and shower head. But if you SUDDENLY lost hot water pressure everywhere in the building, we have some different ideas.

It is unlikely that fixture or strainer or shower head clogging would explain a hot water pressure sudden loss at all plumbing fixtures; usually that clogging builds up over time. Indeed a scrap of mineral crud could break loose and suddenly clog an individual fixture strainer, but the chances of that happening at the same time at all individual fixtures just doesn't seem likely.

...

Possible Point Stoppages or Clogs in Building Hot Water Pipes, Valves, or Heaters

But a similar problem could have occurred right at the water heater, or in water heater piping near the point of hot water origin. For example, a failed, or clogged control valve, pipe section, pipe elbow, or even the outlet at the hot water tank itself could be come blocked.

Clogged piping diagnosis is discussed in more general terms (besides a clogged tankless coil)

at WATER PIPE CLOG DIAGNOSIS

and repairs at WATER PIPE CLOG REPAIR.

But let's distinguish between clogging of runs of water supply piping in a building, and a specific point clog or blockage. Point clogs or stoppages in water piping can occur anywhere in the water pipe system, but are more common at these points:

Illustration: repair parts for a cartridge-type water supply valve from Symmons.

The Symmons No. 17 kit shown here uses brass parts.

Nylon faucet stem cartridge kits, such as found in some Delta faucets and ceramic faucet stem cartridge kits such as used in some Kohler faucets, also have openings that can become debris clogged, though those materials may be less prone to scale accumulation .

• Debris blockage or scale clogging at an individual water control valve 
  
  where a clump of debris or mineral debris can partly block the valve opening
• Clogged hot water valve cartridge
  
  some hot water control valves such as at sinks, tubs, showers, use a replaceable internal valve cartridge that actually starts and stops water flow through the valve.
  
  The cartridge half attached to the valve stem and the cartridge female half are drilled with multiple small holes that permit water flow through the valve when it is in the open position.
  
  These valve cartridge holes can be clogged by mineral scale deposits, corrosion, or debris.
  
  Shown above: A Symmons valve rebuild kit model REB that can be used to repair a Symmons Temptrol valve. Similar repair kits are available from other plumbing manufacturers and suppliers as well as online vendors and Amazon.
  
  See FAUCETS, OUTDOOR HOSE BIBBS - where we include faucet leak repair procedures for several types of faucet leaks.
• Damage blockage at an individual water valve
  
   that might appear to be fully "open" (valve handle turned fully counter-clockwise) but internally in some valve designs if the valve stem breaks, the handle may turn but the valve may remain closed (or open, or in whatever position it was last found)
• Debris blockage in an elbow or bend in hot water piping 
  
  more likely to have occurred closest to the debris source such as near the water heater. If there is good cold water flow and no hot water flow, start looking for a blockage at the point where the hot water supply tees off of the cold water main.
  
• A clogged dip tube
  
  thanks to reader Dave for this tip 2019/05/04. Dave bypassed the water heater, connected cold in to hot out, found good flow at the fixtures, then knew to focus on the water heater.
  
  Customer lost hot water volume throughout the house overnight. Cold water pressure was unchanged.
  
  At the gas hot water tank we unhooked supply line and connected it to hot line with a piece of hose and a couple clamps. Turned the water back on, volume was fine at every fixture throughout the home.
  
  This isolated the problem to within the tank. 3 yr old tank. Hot water present at the relief valve, drained the tank, virtually no sediment in the bottom.
  
  Next I pulled the dip tube and found a 4”-6” section clogged down to a pin hole with scaling. Replaced dip tube after we determined cleaning it out was going to damage it anyway. - Dave 2019/05/04
• A clogged water filter
  
  not likely as this would normally affect both hot and cold water pressure unless someone installed a water filter just upstream of water entering the hot water heater.
  
  Note that some tankless water systems include an anti-scale cartridge type water filter that can become clogged.
• A clog or problem at the water pressure tank
  
  not likely as this would normally affect both hot and cold water pressure

...

Three Types of Plumbing Valves Used on Water Piping: Globe Valve, Gate Valve, Ball Valve Compared

As Carson Dunlop Associates' illustrations below show, a broken water control valve stem can obstruct or block water flow through the valve.

Globe valves (above) tend to most restrict water flow compared with the Gate valve (below)

and Ball valve (below this line).

Watch out: you can be fooled about whether a gate valve is actually open or closed. A a broken stem on a gate valve can also leave the valve stuck partly or even fully closed (or open), regardless of how you may be able to turn the valve handle.

...

Draining the Hot Water Heater Tank to Fix Poor Hot Water Pressure?

Simply draining the hot water tank might not fix the problem because draining alone won't remove a lot of accumulated debris.

For example, a chunk of mineral debris may have escaped the tank and is clogging a pipe, elbow, or valve.

If during draining you found clots of mineral scale, that adds to the suspicion of a scale problem and blockage.

For example, if a chunk of scale happened to flow into the piping leaving the hot water heater tank, or into a valve in the piping system, that could cause a blockage.

Watch out: as Carson Dunlop Associates' illustration (left) shows, for safety reasons we normally expect to see a shutoff valve only on the cold water line into the water heater, not on the hot water heater tank outlet side.

Clues Pointing to Mineral Debris Clogging in Hot Water Piping

• Was the water heater recently more noisy than usual?
  
  See WATER HEATER NOISE DIAGNOSIS, CURE
• Is your water supply high in mineral content?
  
  Take a look at the water heater scale discussion
  
  at WATER HEATER SCALE DE-LIMING PROCEDURE.
• To Flush out Water Heater Debris see:
  
  WATER HEATER FLUSH PROCEDURE - where we explain how to flush scale and debris - which you may have already tried, BUT maybe without recalling the extent of scale you found.
  
  You may need to take another look at the chance of scale or debris clogging a valve or pipe or pipe elbow at the water heater.
• Check for closed or blocked COLD-IN - Also check cold water supply INTO the water heater.
  
  If you open the water heater drain and turn back on the cold water supply to the water heater, and if you do NOT see powerful water flow out of the heater tank drain, then the drain valve could itself be blocked by debris (most common) or alternately you might have poor water flow INTO the water heater.
• Check other water valves -
  
  Check all of the plumbing control valves feeding the water heater to be sure no one closed one of them, and if there are shutoff valves on the hot water piping system ahead of most of the building plumbing fixtures, check those for operation and blockage, too.
• Check water heater pipe connections -
  
  Be sure that the incoming cold water supply is connected to the water heater connector or connection marked COLD
  and
  that the water heater's outgoing hot water is connected to the water heater connector marked HOT
  
  You can read in the reader Q&A below a long multi-step no-hot-water-diagnosis fiasco that ultimately we found that the heater had been plumbed backwards. The water heater's heat trap installed on its COLD inlet fitting was connected to the building hot water supply water heater "out" piping - so NO hot water flowed out of the water heater.

Thanks to Carson Dunlop Associates, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-11-24 by CK Diagnose no hot water: new water heater, no hot water delivered at fixtures - finally traced to backwards piping hookup

Just had a new 80 gallon electric solar water heater installed. Very little hot water is getting to the fixtures.

The pipe coming out of the water heater feels hot, but water coming out of the faucets are not. What is going on here?

Reply by InspectApedia Com Moderator - look first for a closed valve or a restriction or blockage in hot water pipes

@CK,

You asked a perfectly appropriate question but not one that can be answered without a shred of information about your building its plumbing and the solar system installation and its controls.

If the old heater delivered hot water (until it failed)

and

if the new heater is identical to the old one but now you're not getting adequate hot water flow

it makes sense to look for a blockage: a bad valve, check valve, controller, or an improper plumbing connection, etc.

You might want to simply follow the hot water piping to see if there is a valve is closed or a restriction in the hot water piping starting at the water heater itself.

On 2021-11-28 by CK - new water heater was just a swap-out; other pipes not changed

@InspectApedia Com Moderator,

Thank you for the response. This was a direct replacement so everything should have been a simple swap out. Not sure I could provide info about the building and other areas you mentioned.

Reply by InspectApedia Com Moderator - So the problem must be the water heater itself or its connection to the building water pipes

As you did not change any other plumbing and you are dead sure no valves are closed on the cold-in nor hot-out side of the water heater, then the problem has to be with the installation of the water heater itself.

On 2021-12-07 by CK - installer thinks hot and cold pipes were mis-labeled

@InspectApedia Com Moderator, I will have that checked.

The installer thinks that the pipes are mislabeled and is why there is no hot water. I doubt this could be the case but could there be a chance that this is the problem?

Reply by InspectApedia Com Moderator - flying blind: show us a photo of the installation to get bettr advice - hooking up a water heater backwards will give no hot water

@CK,

Yes, though seeing a photo of the installation and knowing the brand, model and checking the instructions would be helpful.

For example if a water heater is hooked up backwards (cold-in connected to hot-out side and hot-out connected to the cold-in side) then it won't work.

That's why water heaters come out of the box with HOT and COLD marked clearly on the water heater top.

On 2021-12-08 by CK - A "tube" was blocking a hot water supply pipe

@InspectApedia Com Moderator, Turns out there was a tube in one of the pipes. Once it was removed, hot water was flowing. Thanks for all the info.

Reply by InspectApedia Com Moderator - what tube?

@CK,
AAA, hot water at last! Good news.

Thanks for that follow-up: it will help other readers facing the same problem.

What on earth was the "tube" in one of the pipes? Which pipe? How did it get there?

On 2021-12-08 by CK - blue tube in one of the "pipes" from the water heater manufacturer

@InspectApedia Com Moderator, Not sure what the blue "tube" was. Since it was a brand new unit, must have been installed by the manufacturer as a safety device or to prevent damage during transit? The blue tube was in one of the pipes.

Sorry didn't see which one it was in since the installer was told to check the unit to see if there was a blue tube in it and there was!

Reply by InspectApedia Com Moderator

@CK,

Possibly intended to indicate which side of the heater was to be connected to cold water inlet. Or a water heater heat trap to keep hot water from flowing back out the cold water inlet;

if so, then

Watch out: your installer may have connected the water heater improperly, sending cold water in on the "hot" side anbd connecting the building hot water supply pipes to the water heater's "cold inlet" side.

On 2021-12-09 by CK - Sun Earth/AO Smith water heater, Model SE80-6

@InspectApedia Com Moderator, I think it was on the cold water side. Sun Earth/AO Smith water heater, Model SE80-6

Thanks for the information and images. I didn't see the "tube" that was actually removed so I can't comment if it is the same as what you sent.

I'll try to see if I can get some information as to what that was for or if it was an oversight by the manufacturer. I'm thinking it wasn't an oversight from the manufacturer as another installer had asked if that tube was removed or not so seems like it is common to be with a new water heater.

On 2021-12-10 by CK - SOLVED: Water Heater dip tube incorrectly installed on water heater "hot" side - prevented hot water from being delivered to the house

@InspectApedia Com Moderator, I was told that the pipe that was incorrectly installed was a dip tube. It was installed on the hot water line and shouldn't have been there. I guess it was put in by the manufacturer by mistake or by the distributor before it was shipped. I was told it isn't needed so the current setup does not have it installed. Lots of hot water so no issue there.

Apparently the manufacturer includes this dip tube in the tank for all the top mount installation options. If installing to the bottom ports, then the pipes need to be removed from the top ports where it is not used.

Reply by InspectApedia Com Moderator

@CK,

Thank you for all your added follow up - this information will help other readers.

In particular, the DIP TUBE belongs on the COLD water inlet to the water heater.

It's job is to be sure that cold water entering the water heater tank is at the tank BOTTOM

In a normal tank type water heater

Hot water leaves the water heater at the heater's tank top - where the hottest water rises by convection as the water is heated.

Cold water enters and is placed (by the dip tube) at the tank bottom - lest it otherwise cool off the hot water at the tank top.

If someone hooks up a water heater BACKWARDS then indeed you won't get much hot water out of the tank since when you open a water tap the water is going to be delivered from the coldest part of the "hot" water reserve - at the tank bottom.

But you DEFINITELY NEED the DIP TUBE..

SO if your water heater was installed backwards (connected hot out to the tank's cold-in and cold in to the tank's hot-out ports) it needs to be corrected if the "solution" was simply to remove that dip tube.

Take a look at your water heater tank.

The manufacturer usually includes a label or an imprint embossed right in the steel tank top saying

HOT by the hot water outlet port
and
COLD by the cold water inlet port.

Now follow your water pipes to be sure that your heater is connected and piped correctly.

Let me know, and post a photo of the top of your water heater showing the labels and connections.

see our copy of Carson Dunlop's sketch for a graphic demonstration of my wordy explanation

And we still want to be sure that the tank is plumbed with hot in to the right port etc.

In Australia, Solar water heater on roof loses hot water flow

We have a solar hot water tank on the roof. We started having flow problems with the hot water about a month ago. (All taps are hot/cold mixers and the cold flow is fine.)

In the morning the hot water flow and pressure is fine. Also at lunch time and again when showering in the afternoon although sometimes the shower hot water pulses for 30 seconds until we get a steady flow.

This is a recent development. However, in the evening the hot water flow to all taps often ceases altogether. Sometimes if the hot tap is left open the flow returns after a few minutes but normally we have to wait until a few hours later for it to return.

Could there be a valve/washer somewhere that heats up and expands and stops the hot water flow? (My very amateur diagnosis!)

The solar tank manufacturer was quite sure (of course) that it was not a fault with the tank. Any advice. Thank you.

Reply by inspectapedia.com.moderator

@Gregory Jones,

Of course the manufacturer says it's not their fault; but ducking and weaving aside, it's too bad that the manufacturer of your solar water heater didn't have someone who could offer even the slightest suggestion.

Usually the manufacturer, if they've been in business for a year or longer, has one or more engineers who have already worked with their customers who have run into just about every snafu imaginable, and some unimaginable ones.

Tell us a bit more about your solar hot water system: brand, model, country and city of installation, system age, and maybe post a schematic or sketch.

I've seen pulsing water traced to a small electric water pump that was pumping against a partly-closed valve or against an obstruction.

But surely the total cessation of hot water flow in the evening is diagnostic.

What's different besides daylight and temperature change?

Are there any timers on the system?

On 2021-10-11 by Gregory Jones

@inspectapedia.com.moderator, Thank you for your response. The hot water system is Solar Hart. It was installed circa 2003 in Canberra, Australia. I have included a photo and (if I can add two + photos) a photo of the plumbing connections - temperate valve and the valve which controls the amount of cold diluting the hot flow.

Reply by inspectapedia.com.moderator - solar hot water tank flow problems

@Gregory Jones,

Have you stepped through all of the valves and controls for this solar water heater to be sure that none of them is closing unexpectedly?

Examples of controls that may affect water flow:

Does your unit use a thermo-siphon flow restrictor valve? Is that valve sticking? Have you tried replacing it. [ 344391 (TRV) ]

Your unit uses a temperature limit device that will shut off flow through the collectors if temperatures are too high; I agree that temperatures drop, rather than rise, at night, even in Australia, but I'm not sure what a bad control might to.

Does your unit use an in-series continuous flow gas booster to protect against Legionella?

Is there a flow control associated with the manufacturer's recommended electrical temperature booster?

Is there a temperature control bypass valve?

When you have no hot water at a tap, if you go to the solar water heaters temperature-pressure relief valve and open the test lever does water flow?

Have you checked your system's pre-charge pressure against the IO manual's instructions and matched it to the pressure-relief (PR) valve specs ?

For other readers:

If you don't already have it, you can download the

• SOLAHART WATER HEATERS INSTALLATION & OPERATION MANUAL [PDF] (2016) Solahart Industries Pty Ltd
  (ABN 45 064 945 848) PO Box 7508, Rydalmere NSW 2128, Australia Web: https://www.solahart.com.au/
  
  - original source: https://www.solahart.com.au/media/3409/33-1197_j-solahart-thermosiphon-owners-manual-2016-january.pdf
  
  Or give the company a call
  
  Australia
  For SERVICE Telephone - 1800 638 011
  or your nearest Solahart Dealer
  For Sales Telephone - 1300 769 475
  

also see

SOLAR HOT WATER HEATERS

On 2021-05-28 by Yvonne Rojas - suddenly lost all hot water pressure

We suddenly lost hot water pressure [only] in the whole house, a month ago (15 year house 2 stories). My husband checked valves.

He then ended up working on the water heater and we we had hot water again. Less than a week later, same thing. He worked on the water heater again and the hot water came back.

Last night after we showered in different bathrooms at different times, we heard a bang. Both full bathrooms are upstairs. Downstairs has one half bath. We realized we had no hot water at all in the house. The cold water still worked and pressure was normal. Tonight we prepared to take cold showers.

The master bedroom bathroom shower had no hot water and only a trickle of cold. The separate garden tub in the same bathroom had only cold water and pressure was fine. The sink faucets only had cold water and pressure was fine. The guest bathroom had no water in at all in the tub/shower. There was cold water in the sink.

Less than 5 minutes later my husband opened all faucets in both bathrooms and hot and cold water came back. Full pressure. Same for other faucets downstairs. What is causing this issue?

Reply by danjoefriedman (mod) - suddenly lost hot water pressure

@Yvonne Rojas,

Certainly you are describing a hot water problem with deserves prompt diagnosis and repair, but unfortunately even with the length of your note I haven't a shred of information about your plumbing for your hot water system.

In order to diagnose a hot water problem we need to know some basic things such as how the hot water is made, how water is provided to the building, is it municipal or private well, and what controls are installed on the system such as tempering valves and check valves.

Take a look at my response to reader Toby below as a starting point.

 

On 2021-05-18 by Toby - Hot waterstarts hot but after a minute loses pressure then flow nearly stops

The hot water in my house starts out really hot with normal pressure, but after it’s ran for about a minute or two it loses pressure really bad and the temperature starts to decrease ,after about five or six minutes the water is lukewarm and barely trickling out of the faucets.

The cold water supply line does not lose any pressure at any time so I don’t understand why my hot water pressure is not maintained.

This problem just started about three weeks ago ,before that it was normal pressure and good hot water it would fill the bathtub for a bath and now it won’t even fill my bathtub halfway. Any suggestions?

Reply by danjoefriedman (mod) - watch for debris clogging or a hot water tempering valve clog or malfunction

@Toby,

I'm puzzled too, but then I can't see much of the details of your hot water system from here.

Check to see if there is a tempering valve or mixing valve that is malfunctioning.

I've also seen this problem when there is a lot of debris in the water heater;

When no hot water is being run, debris settles to the bottom of the water heater tank.

When you turn on hot water it flows at first, but incoming cold water to the water heater tank stirs up debris causing it to block the hot water outlet.

On 2021-03-26 by Brad - no hot water at some fixtures after I changed a water heater element

I've changed the heating elements I changed the thermostats and now I have no water at all to the kitchen sink but water to the tub, toilet and washer...... help me out here

Reply by (mod) - clean the faucet strainer of debris stirred by your work on the water heater

@Brad, I am guessing that you are talking about changing components and an electric water heater. If you know have no water at all either a valve was left closed or the activity at the heater has stirred up debris that has clogged its input or outlet.

On 2021-02-17 by Larry - Texas deep freeze points out cause of a water heater problem

During the deep freeze in Texas the hot water stopped flowing to all faucets in my house (0 flow). The cold water flow is normal. I opened the TP relief valve briefly and hot water comes out of it.

Also the cold inlet gets "more cold" when the valve closes. The hot water heater is electric, it is located in the garage, I have been running a space heater in the garage and the temperature there is now 50 degrees, any thoughts? I really need a shower

Reply by (mod)

Larry

So the frozen point is somewhere in the common cold-in to the water heater or in the hot-out from the water heater before it branches off to all of those various locations.

Take a look at the suggestions at PIPE FREEZE-UP POINTS

and then grab a hair dryer and see if you can thaw the freeze-point; when you find it you'll know where you need to add a heat source and fix cold drafts so as to avoid having the problem over and over.

On 2021-01-03 by Steve - Good hot and cold pressure everywhere except Kitchen where "hot water" is just warm

I have normal pressure from both hot and cold faucets throughout the house. Hot and cold work as expected everywhere except the kitchen.

Cold water is cold and pressure is fine. Hot water is just warm and the pressure is fine.

If I turn off the cold water valve under the sink, the cold water is off.

Hot water is unchanged, still good pressure but water is just warm.

Reply by (mod) -

Steve:

I would follow the hot water piping en route to kitchen, insulating it and making sure that it's not exposed to a cold draft.

On 2020-12-21 by Dion - recurrent water filter clogging trouble

In the tempering valve there’s 2 little filters that clog up it cost me 100.00 dollars for a plumber tell me and show me how to clean any onging it comes back I had the same thing happen new hot water system 2 days later very low hot water pressure

On 2020-12-21 - by (mod) - study water source debris type to diagnose and fix the clogging problem

Dion

I would look closely at the debris that is clogging those filters to see if you can identify it and therefore trace it to a source.

There may be a different problem that can be found and corrected to stop producing the debris.

For example a deteriorating anode in a water heater can produce a large volume of particulate debris.

You might also check faucets trainers in the home to see if the debris is appearing everywhere.

On 2020-12-06 by Carly - suddenly lost all hot water pressure days after new electric water heater was installed

I bought a new electric hot water and the hot water ran for a few days then all of a sudden I lost all pressure and just started trickling out of all my faucets but my cold water has perfect water pressure.

What could be causing the restriction of my hot water pressure when the cold water has perfect pressure? And like I said it ran for days before it came to only a trickle.

Reply by (mod) - clog at the water heater inlet or outlet

That sure sounds like a clog at the water heater inlet or outlet.

A sudden and near-total water pressure or flow rate loss can happen if, for example, a bit of water filter material escapes or a chunk of pipe scale breaks away to move to a nearby pipe elbow or tee where it blocks water flow.

On 2020-06-26 by Kent. G. - only cold water comes out of my water heater

I've got cold water going into my water heater but no hot water in the hot water pipes inside the house I disconnected the hot water Outlet hose from the top of the water heater and I've got cold water coming out of the outlet hose that should be going into the house from that hose

Reply by (mod) - no hot water in pipes in the house

Kent

From your description it sounds as if the water heater is not operating at all.

So let's start at step 3 in the "no hot water" troubleshooting sequence above on this page.

On 2020-05-28 by Michaela - no hot water after installing new faucets

Everything worked fine before I changed out the faucets now when one shut off is off the other don't flow any water through in my bathroom faucets.

When they are both open no issues. Any ideas?

Reply by (mod) - clean faucet strainers

Michaela

Is the "shut-off" valve you are discussing ahead-of both faucets?

Are the two faucets on the same fixture (unlikely) ?

Often when we do plumbing work the soldering or other plumbing work releases debris that clogs faucet strainers - try cleaning those.

Diagnostic tip: when you say you have water flow only when "both faucets are open" could you be seeing that only HOT or only COLD water flow is blocked?

On 2020-05-18 by Tyler - good water pressure until the water gets hot

When I turn on the hot water in the kitchen it flows perfectly until the water turns hot.

The other fixtures all have steady, regular hot water. If the hot tap was always slow I would suspect blockage but since it only slows when the water warms up. Any ideas?

Reply by (mod) - check for well pump problem first

Tyler that's quite baffling, I agree.

Is it possible that you're running water for a time to wait for hot water at the tap and that your water system uses a water pressure tank whose delivery pressure falls (as is normal) until the pump turns on?

On 2020-04-04 by gen

turn the main valve off for the hot water to have a pipe fixed a few weeks ago

I just went to turn the hot water back on it came out for a few seconds and then totally stopped but yet my cold water continues to work just fine what could it be I only turns one valve off and that's the main

Reply by (mod) - turned off hot water then back on but no hot water flow

Gen

I suspect the valve is clogged or broken. Particularly if it's a gate valve, it's possible for the stem to break away from the actual valve closing internal gate.

On 2019-12-28 by George Schuler - mixing valve on hot water tankless or tankless coil itself may be clogged: only can run one shower at a time

I have two showers in my house. **ALL heat and hot domestic water is provided by oil fired boiler**

Only one shower can be used at a time or the pressure drops to a trickle. In fact if one is in use and hot water is turned ANYWHERE else in the house the same thing happens.

There is a mixing valve in the system as well as a circ pump. Finally, the overalll pressure is slighter better in cold supply than hot water. Any ideas?

Reply by (mod) - inadequate hot water flow rate

If your hot water is be made by a tankless coil is quite natural that the flow rate through the coil would be limited to start with.

Otherwise the flow rate of water would be too fast for the water to be heated. In addition that that's the most common location for mineral scale clogging.

The fact that hot water pressure is less than cold can be a confirmation of a scale clogging problem.

On 2019-10-23 by Larry - when I flush any toilet water pressure drops to zero

I work in a 5-story building the pressure with a gauge on this spickets at 60 lb when I flush any toilet it drops to zero and the other toilets won't flush what's the problem

Reply by by (mod)

Larry

Thanks for an interesting question; when we see high pressure in pipes (when no water is flowing out) and then a big pressure drop when any fixture (such as a toilet) is on, we suspect that the problem isn't pressure but flow rate.

The flow rate is affected by clogged pipes or small diameter pipes.

So you could have great 60 psi pressure measured when nothing's running but the pressure will drop way down and the flow rate will be terrible if pipes are constricted in diameter for any reason. That might be rust in old galvanized iron pipes or mineral scale in copper or iron pipes.

On 2019-08-07 by Angelo- intermittent loss of hot water pressure throughout whole house

Over the last 2 weeks, I would occasionally lose hot water pressure throughout the house.

I have figured out that if I turn on the hot water at the laundry basin in the basement, it will restore pressure. .thoughts?

Reply by (mod) - if I turn on the hot water at the laundry basin in the basement, it will restore pressure.

I'm baffled and blind here as I can't see and follow the hot water piping in your building. Is it possible that

there is an intermittent clog in the water heater or hot water tank that's being dispersed when you run hot water faster?

I see this problem sometimes when using hot water stirs up debris in the water heater, clogging its outlet.

...

Continue reading  at HOT WATER PROBLEM DIAGNOSIS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see HOT WATER PRESSURE LOSS FAQs - diagnostic questions & answers on lost hot water pressure, flow, temperature

Or see these

Recommended Articles

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  • TANKLESS WATER HEATERS
  • WATER HEATER COMPARISONS, PROPERTIES
  • WATER HEATER SIZE SPECIFICATION
  • WATER HEATER TEMPERATURE TOO COLD or TOO HOT

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