Hot water supply loss troubleshooting FAQs:

Questions & answers on how to diagnose the cause and decide the cure for rapid or sudden loss of hot water pressure at plumbing fixtures in a building.

This article series explains how to diagnose the loss of hot water pressure, quantity, or flow in a building.

Page top: basic parts of a gas water heater, and sketch below showing a tempering valve with at tankless coil for making domestic hot water are provided courtesy of Carson Dunlop Associates, a Toronto home inspection, training & report writing system company.

FAQS on Loss of Hot Water Pressure & Flow in a Building

These questions and answers on loss of hot water pressure were posted originally

at HOT WATER PRESSURE LOSS - be sure to review that article which includes

• DIAGNOSE NO HOT WATER AT ALL
• DIAGNOSE WEAK HOT WATER PRESSURE (FLOW) at SOME or ALL FIXTURES

Also, 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.

Shown at left, a tankless coil used for making hot water in a heating boiler, courtesy of Carson Dunlop Associates, a Toronto home inspection & education company.

 

We have good cold water pressure but no hot water at all

I have no water coming from any hot water taps in the house. Don't hear or see any leaks, hot water tank feels empty. Any idea what could be causing it? It is a gas water heater. On 2017-08-31 by Brian

by (mod) - If you have cold water but no hot water

If you have cold water but no hot water, and moreso as you think the water heater tank is empty, you want to first turn OFF the water heater promptly for safety and to reduce the chances of damage.

Then I would look for a valve that's closed or a pipe or elbow or fitting that's blocked looking backwards from the water heater along the incoming cold water to the unit.

I'd start by looking at the gas water heater - does it turn on ?

For NO HOT WATER at all - which is your case - I suspect the heater is not running. That could be from a variety of problems: leaks, no gas, bad igniter, bad thermocouple, or an unsafe chimney whose spillage shuts off the system, or something else not guessed during this arm-waving speculation.

Take a look at the NO HOT WATER PRESSURE and let me know how that works for you. (We also have posted articles on gas water heater inspection, diagnosis, repair - just use the InspectApedia search box for GAS WATER HEATER)

 

Good cold but weak hot water pressure: why?

On the tub I turn the hot water on but It barely comes out cold water comes out good what can be the problem ? On 2017-03-06 by Anonymous

by (mod) - If you have cold water but weak hot water

If the poor hot water flow is only at this one fixture then I suspect that a hot water pipe or elbow or control close to the tub itself is clogged or closed.

If it's at all fixtures then the blockage originates at or closer to the water heater itself.

No hot water at taps after installing new electric water heater

I have an electric hot water heater and put a new element in it and the tank is hot around the element and valves going into the tank. BUT when we turn on the faucets no hot water. On 2017-08-12 by Tim

by (mod) -

If when you turn on your water heater and then red hot water and got air out of your faucets there's a good chance that you had not removed all the air from the water heater tank and an element that was not in water but in air simply burned up

If there is actually NO water coming out of the hot water tap, then you probably left a shutoff valve closed on the hot side of the water heater.

No hot water after we replaced our water heater

We replaced the hot water heater. Cold water, out of cold faucets works great, but no hot water at all. When we turn on the hot faucet no water comes out. We've checked. A bunch of possibilities, but no luck so far. Thanks

Actually water does come out of the hot side, it's just cold On 2017-07-25 by Linda

OK so you have water flow at the hot water faucet but it's not heated - so we know the water heater isn't heating.

Is this an electric water heater? Was it turned on before the tank and piping were purged of air? That would destroy the heater elements.

 

No hot water after an electrical power outage

Power outage twice then water heater stop heating On 2017-03-16 by Anonymous

by (mod) - check the reset-button on the primary control

Was the outage from an external source or is your own building's electrical wiring and service unsafe?

Check the reset buttons on the heater's thermostat or primary control.

 

Lost hot water after a street water main broke

is it a coincidence that a water main busted down the street . City shut off the water and coincidentially my hot water pressure has been non existence since they out it back on? The fire hydrant across the street has been drainin
g full blast for 5 days On 2017-06-02 by johnny d

by (mod) - check for debris clogging in your water pipes

Occam's razor would argue that it's probably not a coincidence.

You would think that if debris was introduced into the plumbing system from a water main break that both cold and hot systems would be exposed to clogging. But it's possible that debris only clogged A fitting or valve at your water heater.

Hot water loss traced to damaged / clogged water heater dip tube

Encountered this problem today. Customer lost hot water volume thruout 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.

Issue resolved. On 2019-05-03 by Dave

Dave

Way to go, and thank you for posting both the diagnostic procedure and the results. That will certainly help other readers.

I've found a range of dip tube problems over the years but not the scale clogging that you reported.

It's interesting that the dip tube was scaled but the bottom of the heater was not - suggesting that maybe the dip tube was also working as a sacrificial anode but collecting scale - was this a metal dip tube?

I've added your helpful comment into the text of the article above at

HOT WATER PRESSURE LOSS CLOGS https://inspectapedia.com/plumbing/Hot_Water_Lost.php#ClogPoints

and will welcome further critique or suggestions

No hot water in laundry room after plumbing work

I switched my hot water pvc pipe from over head to floor and extended my line from the line for my washer now I don't have no hot water in the house but I do have it in the landry room On 2019-04-15 by James Alford

by (mod) -

"No hot water" needs more basic description before one can comment usefully:

Do you mean that water flows but it is never hot or do you mean that there is zero water flow at the hot water faucet?

Still it sounds as if you've missed a connection or you left a shutoff valve closed.

Less likely but also possible: if you're not expert at soldering copper pipe (if that's what you used) you could have over-filled a joint with solder and blocked a pipe.

Sudden loss of hot water just in our upstairs of house

We have sudden loss of hot water just in our upstairs of house. Three faucets on main floor have good hot & cold water. Turning on any of the 4 upstairs hw valves - no water comes out.

However, if we turn on one of the upstairs cold water faucets, then water will come out of the other hw faucets, that water is cold. On 2019-01-21 1 by kms

by (mod) - first check for a closed valve

K

I think you need a plumber on-site, but before calling someone, just follow the hot water pipes, looking for a valve that might be closed or clogged between the point where the downstairs and upstairs hot water supply piping splits off.

First be sure nobody closed a valve controlling upstairs hot water: follow the hot water pipes from where the hot water line leaves the water heater or calorifier

NO hot water in nkitchen after we worked on a pipe leak

Fixed leaky pipe coming off hot water heater. Now we have hot water everywhere except kitchen? On 2019-01-01 by Greg

by (mod) - no hot water after working on water heater

Look for a valve you forgot to re-open or that's become debris clogged. Follow the hot water pipes - feel for the cold area.

No hot water anywhere after I replaced shower handle cartridges

Hi! I replaced two shower handle cartridges and now I have no hot water pressure anywhere in the house. I drained the hot water heater, and refilled it. Very little sediment came out (the tank is 4 years old). I've taken off the hot water pipe coming out of the tank and it is clear. Help! On 2018-10-05 by Debbie

by (mod) - check for a clogged dip tube in water heater

Perhaps debris from a disintegrating dip tube clogging the outlet

If you have no hot water pressure even at the fixtures where you didn't change anything I suspect that there is a shut off valve that turned closed and is not reopening.

by Debbie

Great idea! I'll check that this evening. If it is disintegrating after only 4 years, I'll be calling the company! I'll let you know how it goes. Thanks!

by Debbie

The only shut off valve I closed was the main. The cold water shut off on the tank doesn't work. The tank refilled with cold water and there is plenty of cold water pressure.

So should I drain it again and remove the heater drain to see if it is clogged? Would that keep water from flowing into the house?

by (mod) -

I wouldnt keep draining ... thinking...

If you can do so without risk that you can't close it again, or flooding,

If you open the heater drain does it flow freely and dies water enter the geater?

If so, maybe debris clogged the tank outlet.

by Debbie

I did remove the hot water outlet tube and snaked it and it is clear.

Water flows out and then dies down. It flows fine when I open a hot water tap in the house.

Opening the tap is orobably just letting air in and allowing the tank to drain.

 

Hot water comes out for just a second, then stops completely - later it worked OK

Hi. Can you tell me what happened here. All of a sudden I only had cold water and hot water would not run out of any faucet in the house.

If I turned hot on, it would come out for a split second and then just stop completely.

No leaks, everything open by the tank. I turned the tank off and turned temperature off, then back on and put temperature up.

Then after about three hours, I tried it and It started working normally. What could have caused this? I believe my tank is less than ten years old. Should I be concerned this could happen again? Thank you for any insight. On 2018-08-02 by victoria

by (mod) - sounds like debris or a loose part in the hot water valve or at the tank

Very odd indeed, Victoria, to have complete loss of hot water flow but continue to have cold water flow, and then to have the hot water flow return on its own. If nobody closed, then re-opened a hot water supply valve I'd start at the hot water source - you don't say how your hot water is made - to look for a timer or control or clog problem.

I Turned off water heater to get my son out of the shower, now no hot water upstairs

Turned off hot water heater to run son out of shower and now hot water will not run upstairs. On 2018-05-16 by Lisa

by (mod) - possibly a broken valve stem

Lisa,

I used that same trick to drive my daughter Mara Elise out of her endless showers. She never knew it.

But if you were seeing hot water in some places of your home and not others, and if you are turn off of hot water was directly at the water heater, then the problem is something else.

Perhaps a clogged water line or valve close to the fixture where you're not saying hot water.

Washing machine causes loss of hot water in other areas

When I start my washing machine and it is filling with water. I lose hot water pressure in my kitchen and bathroom.

I only use cold water to wash clothes the hot water is hooked up to my washer but the valve is not on. My cold water pressure is fine. On 2018-04-06 by Jennifer

by (mod) -

I admit that this is a baffling question. In particular of the cold water pressure continues to function, and if I touch you confirm that only cold water is entering your washing machine, then the only wild guess that occurs to me is that the routing of the supply piping in your building is such that the cold water into your washer is in essence taking priority from the cold water supply that would be entering your water heater.

That's possible depending on building routing and valve configurations. Your plumber will no doubt want to Simply follow the pipes and see how the water is routed.

 

Are there water flow restrictions inside a water heater?

Does anyone know if there is a restriction inside a hot water heater itself.

We had great water pressure, then installed a new water heater now we have low pressure on the hot side.

We have checked all pipes an cut off valve. They are not clogged and the valve is working great. What else could be the issue. We are on well water.

Also when we unhook pipes an run them the flow is great. And when we bypass the water heater the pressure on hot water side is back up. So what can cause this if anyone has any ideas.

Could it be an issue with the water heater tank itself blocking the pressure or something On 2018-02-11 by Christal

by (mod) - where water flow restrictions occur in a water heater

A new water heater tank should not cause a reduction in hot water flow.

However it's easy to block a control valve, dip tube, or even piping near the water heater if excessive solder was pushed into a solder joint.

I just replaced my shower and tub valve i shut the main off.upon turning the main back onim not getting any hot water through whole hs

Hi my name is Marla I have no hot water or pressure throughout my house. everything was working before I changed my tub and shower valve upon turning the Maine water line offeverything thing was great before that the valve is installed now no hot water through out the house and the pressure is ultra low can you help plz? On 2018-01-27 by Maria

by (mod) -

You want to find what control valve has been left shut, by following the water pipes from the water entry point at the building.

by Marla

@I just replaced my shower and tub valve i shut the main off.upon turning the main back onim not getting any hot water through whole hs,

Thank you Dan but I do not have a well

After we run hot water for a bath all water flow slows to almost zero

When we run the hot water for the bath it runs perfectly for a while then the water flow slows down almost to a stop. Our system is pressurised could this be as a result of the diaphragm in the tank over the pump? (I tried increasing the pressure to 3 bar and it dropped to 1.) On 2018-01-27 by Richard

by (mod) -

The problem sounds to me as if your water pump pressure control switch is debris clogged and is not sensing water pressure - or you are running out of water in a well.

Sudden loss of hot water, cold pressure is OK

We suddenly lost hot water pressure about 2 days ago throughout the house, cold water pressure is good.

We attempted to drain the tank ( as suggested in several articles) but only 15-20 L came out, and the water was crystal clear, no cloudy sediment or rust, but pressure is even worse now; strong for first few seconds and then drops significantly almost to a trickle. Tank is only 6 years old, plumber I spoke to said to replace the tank. Any suggestions? On 2017-12-28 by JAG

by (mod) - clogged dip tube or water outlet: debris in the heater

Sounds like a blocked or damaged dip tube at the tank inlet or a bit of debris blocking the outlet

Loss of hot water at some fixtures - suspect faucet clogs

Here's a situation that has me stumped. In the Master Bath we have double-sinks, a shower stall, and a soaking tub. Until recently we had no difficulty getting hot water anywhere. In the last couple of weeks we stopped getting hot water in the tub - but we get cold water running if we turn on the hot valve.

The hot and cold valves are separate; they are not, as far as I can see, mixed, unless they are somehow mixed back in the wall. We still get hot water to both sinks and to the shower, but for some reason not to the tub. This makes no sense to me. any ideas? On 2017-12-27 by Mr. Tucson

by (mod) -

Like you I suspect a foul-up inside of the faucet assembly.

The fact that you have hot water at the sinks in the same bath suggests that indeed the problem is in the faucet assembly.

Typically at a tub there are two separate handles - hot and cold - plus a third shower diverter control. Getting cold water when the hot valve is opened, while that's happening only at the tub, makes me think that there might be a mixing valve or anti-scald valve, perhaps built into the tub controls or preceding it, that is not working.

Signs of blockage somewhere in our hot water piping

I am having a similar issue... in the apartment building i own, i evicted someone. apartment has been empty for 2-3 months. now i realize there is no water that comes out when faucets or shower are in the hot position.

there is just NO water out of the hot side, but the water comes out fine from cold side. i felt pipes on electric water heater, the pipe leaving the tank is warm. so i know the tank gets power and heats fine. i lifted the pressure relief valve, and seems like no pressure inside tank, no water escapes when i lift the pressure relief valve. the cold water supply into the tank, there is a gate valve with a drain nub.

i open the drain nub on the gate valve controlling water into the hot water thank and it squirts out water so i am inclined to say the water supply is ok into the tank, unless the gate valve is blocked completely internally?. any idea what the problem could be?

seems a blockage someplace. there is zero water that comes out from the hot side of bath and kitchen faucet, and shower. so all hot water in the apartment doesnt come out low pressure, doesnt come out warm, doesnt come out cold.... just bone dry from any hot faucet. any help would be greatly appreciated. On 2017-12-07 by samm

by (mod) -

it's possible that the gate valve that is intended to send cold water into your water heater is in the closed position.

It's also possible that the valve is broken internally so that even when you think you have opened it it is remaining closed. This is particularly true with gate valves as opposed to stop valves.

Hot water flow slows down everywhere. Rental water heater company says their tank is fine

When turn on the tap we have hot water for 1-2 minutes then it slowly dissipitated. Turn off for a coupl eminutes can get hot water then the same problem It happens for all faucets in the house. technician from water heater rental company said there is no problem with the water tank (3 years old). What arethe causes? Help! On 2017-04-20 by Anonymous

by (mod) -

Anon:

If your hot water supply lasts only 2 minutes something's wrong and you ought to ignore the water heater technician's opinion and ask to speak to someone with more experience - or honesty.

It would, of course, help alot to know what sort of water heater is installed: type, fuel, location.

by Anonymous

Many thanks for you prompt advice. Water tank is GSW , gas water tank 50 gallon located next to the gas furnace in the basement

by (mod) -

Anon

The GSW-50 is a gas fired (probably yours is natural gas-fired) water heater that vents by natural draft to the outdoors.
You should then have copious hot water - actually more than 50 gallons, if the water heater has been at rest long enough to fully-heat its
water volume to its cutoff temperature.

Hot water tends to migrate to the top of a vertical water heater tank, so if something's wrong with a control, OR if someone has already used most of the hot water in the heater (or depending on where you live the hot water cylinder, geyser, or calorifier - synonyms), then the remaining hot water volume could be small.

One of the first things I'd check is whether someone has already been using hot water that you didn't realize, such as running laundry.
Second when the hot water runs out I'd dash over to the water heater to see if its gas burner is on. If it's not, then there is a burner or control problem to be found and fixed.

GSW rents water heaters but keeps their specifications SECRET from the public - as their PDFs are all locked.
The company lists their rental water heater specs as PDF files at
http://www.gsw-wh.com/en/resource-library/spec-sheets-and-manuals
but notes
Documents are locked, please contact your rental company to obtain your password.

So see if you can contact your rental company, then use our page top or bottom CONTACT link to either share a downloaded PDF file for comment or give us the PW and we'll help you take a look.

The company's FAQs do not include help with the question of running out of hot water. But from your description I suspect that there is either a failure of the water heater's control (thermostat or gas valve) OR there is an external explanation (hot water being used elsewhere)

GSW can be contacted directly for technical support at
GSW Water Heaters
599 Hill Street West
Fergus, Ontario, Canada N1M 2X1
T 1.888.479.8324
Website: http://www.gsw-wh.com/

No hot water, just air, after water main break

The water company had a main line break so I had no water . Now I have cold water but the hot water is just air ? On 2017-04-03 14:53:43.268294 by Donna

by (mod) - turn off electric water heater immediately; other water heaters - different steps

Donna:

Watch out: If your water heater is electric TURN IT OFF right away then come back here for more comments

Depending on water heater location and plumbing routing and work on the water lines, air could enter the hot water tank or cylinder following loss of water pressure (particularly if your home does not have a working backflow preventer that keeps your house water from flowing backwards into the city water main during a water pressure loss).

Air will normally be purged from the water heater tank when water pressure returns, simply by opening hot water faucets until air stops blowing out and water begins to flow.

It is AFTER air is purged from the water heater (or depending on where you live, calorifier or geyser or cylinder)) THEN you can turn ON the water heater.

Particularly if the water heater is an electric unit, if it is turned ON while NOT FULL of water, the heating elements can burn out in seconds.
If that happened the elements will need to be replaced.

No hot water even though we replaced the gas water heater

Bought a brand new gas hot water heater, hot water only last about 5 mins in some areas and no hot water at all in other areas.

however if you turn on sink in bathroom, shower will stay hot indefinitely upstairs and sometimes downstairs, seems like when other water is running somewhere in the house, some of the fixtures will be hot.

sooo confused, had 3 plumbers look at it cant figure it out. bought a 2nd hot water heater 6 mos later,because they said it was the water heater, same problem. On 2016-10-25 by Lynn'

by (mod) -

Start by watching the water heater when you're running hot water: is the burner on and running? Is the outlet pipe hot? How big is the heater?

 

Poor hot water flow just at some locations in my house

I have an indirect fired hot water heater with low hot and cold volume and pressure in my kitchen sink and my upstairs shower. All other faucets are fine. Plumbing and burner issues have been eliminated so we suspect the hot water heater. Any ideas on how to remedy this?On 2015-11-26 by Jeanne Franzone

by (mod)

Jeanne

As you have good hot water flow at other fixtures the problem is not a system issue but rather a clog unique to the poor-performing fixtures.

Look for a mineral scale or debris-clogged strainer or faucet; if the flow is good when you remove a shower head or faucet strainer you've found the trouble. If not, then look for a clogged valve or elbow or pipe in the water supply to those fixtures.

...

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

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• HOT WATER PROBLEM DIAGNOSIS - home
• HOT WATER IMPROVEMENTS where we diagnose lost hot water pressure when cold water pressure is OK.

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