How to get more hot water.

This article explains how to improve the total quantity of hot water available from your water heating system.

The steps you need to take depend on the type of water heater you're using and on an accurate diagnosis of reason that you're running out of hot water or the reason that hot water pressure is too weak.

We also discuss how much hot water to expect from your water heater.

We give hot water quantity improvement suggestions and we list detailed diagnostic procedures to fix insufficient hot water quantity or flow.

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

What Determines Hot Water Quantity or Faster Hot Water Flow

Watch out: before you start fixing or buying stuff to correct a hot water problem it is important to have diagnosed the actual cause of the trouble.

So if you haven't already done so, see WATER HEATER PROBLEM DIAGNOSIS to be sure you're fixing the right problem.

Article Contents

• WHAT DETERMINES HOW MUCH HOT WATER YOU'LL GET?
• STEPS to INCREASE HOT WATER QUANTITY
• STEPS to IMPROVE HOT WATER USE EFFICIENCY
• EXTRA TANKS FOR MORE HOT WATER?
• INSULATE HOT WATER PIPING?
• INSTALL LARGER DIAMETER PIPING?
• INSTALL A LARGER WATER HEATER?
• DON'T CONFUSE HOT WATER QUANTITY with HOT WATER "PRESSURE" or FLOW RATE
  

Factors that determine how much hot water you get out of a water heater tank

First we'll look at hot water quantity determinants that are independent of the water heater fuel and type. Then at the end of this list we'll point to water heater type and water heater defect or troubleshooting diagnosis and repairs that may be needed.

Factors that determine just how much hot water you get out of a water heater of a given size (that is without changing the size of the water heater tank) are:

• The setting of the water heater temperature dial -
  
  setting the water heater temperature up increases the heat, allows mixing in more cold (manually or at a tempering valve to avoid scalding), thus giving the effect of more total hot water that can be drawn
• The temperature of the incoming water supply
  
  that enters the water tank - that is, how cold is the incoming water?
  
  Colder incoming water cools down water in the water heater tank.
  
  Therefore even if we start with a 50 gallon water heater whose water contents is fully heated, as soon as we start drawing off hot water (someone turns on a hot water faucet) cold water is entering the tank to make up the volume of hot water that was withdrawn.
  
  Typically cold water enters the bottom of the tank and hot water leaves at the top of the tank, assuring that the water drawn off is as hot as possible.
• Condition of the water heater tank dip tube:
  
  Even so, especially at higher water pressures (or if the dip tube in the tank that carries incoming water to the tank bottom has been corroded, become leaky, or fallen off), the cold water entering the water heater can stir up water in the tank, mixing with and cooling down the water inside so that before a full 50 gallons of "hot" water has been drawn off, the outgoing water temperature will be cooler, or even tepid.
• Exposure of the hot water pipes to cold temperatures 
  
  where they pass through the building - losing heat to the building or to outdoors
• The flow rate of water through the building piping
  
  in gallons per minute (larger diameter pipes, valves fully open, higher water pressure) means that hot water may be run out of the tank "faster" or "slower" - this does not change the total quantity available, just how fast you use it up.
  
  So there is a trade off between how long we can run hot water and hot water supply pressure, as we explain
  
  at LARGER DIAMETER WATER SUPPLY PIPING.
  
  Also see WATER PRESSURE MEASUREMENT.
• The recovery rate of the water heater
  
  how fast the water heater can put heat back into water in the tank when the tank temperature drops below the "cut-in" setting on the water heater temperature control.
  
  A water heater with a fast recovery rate (such as oil) will put heat into the tank faster than a slow-recovery water heater (such as electric water heaters).
  
  A faster recovery rate water heater may be able to deliver a bit more hot water before the outgoing water feels tepid.
  
  See WATER HEATER RECOVERY SPEED COMPARISONS for details.
• The kind and size of water heater you are using

The total amount of hot water that can be delivered from a water heater or calorifier also depends very much on water heater size, fuel, type, and other design properties. For water heaters of teh same size in volume, the speed with which the heater can put heat back into incoming water depends on the heater's fuel and design.

See details at WATER HEATER COMPARISONS, PROPERTIES

• The condition of the water heater itself: is it working properly.
  
  If the hot water deficiency is due to something in the water heater itself, you'll see that the steps you take may vary depending on the kind of water heater involved.
  
  See WATER HEATERS - home - for our complete list of diagnosis and repair articles for every kind of water heater/geyser/calorifier/geyser (synonyms for "hot water heater")
  

Steps to Increase Hot Water Quantity

Here we'll summarize what to do if you run out of hot water too soon.

Having a greater quantity of hot water (more total hot water volume available) also opens the way to taking steps to improve hot water pressure and flow rate in a building. On the other hand, if we increase hot water pressure or flow but lack adequate hot water quantity, the result is we just run out of hot water faster than ever.

The approach to improving hot water quantity itself involves these ideas:

1. How is hot water being made? 
   
   Start by understanding what you've got installed.
   
   A water heater tank? How big is it in gallons or liters? A tankless coil? Tankless coils have no stored hot water quantity but depends on boiler size and flow rates. An instant water heater?
   
   Instant or point of use demand water heaters have no stored hot water quantity and depend on the heater size and flow rate capacity. If you never had enough hot water ever, keep this category of problems in mind when reviewing our hot water quantity diagnostic articles just below.
   
   For example, if your heater is electric, and if the lower heating element has burned out, the total quantity of hot water from the heater would be significantly reduced. By contrast if the upper element is burned out the total quantity may not be reduced but the temperature of the hot water will be lower.
2. Has something changed in the hot water supply?
   
    If you used to have more hot water but it has become reduced, there is a problem to find, diagnose, and fix such as mineral scale insulating the water heater tank, a leaky water heater tank dip tube, an electric water heater with one of its elements burned out.
   
   If something has changed, keep this in mind when reviewing our diagnostic list below.
3. Define hot water quantity, flow & pressure clearly.
   
   Quantity of hot water means the total volume of hot water available. Flow rate of hot water, is the gallons per minute of hot water delivered somewhere (out of the heater or at a plumbing fixture). Hot water pressure, as most folks mean it, refers to the flow rate at the fixture.
   
   To a plumber, pressure is measured not in gallons per minute, but in pounds per square inch or an equivalent. Your water supply system might sit at 50 psi of pressure when everything is turned off.
   
   When you turn water on, the actual psi of water pressure that you could measure at a fixture will depend on the source supply psi (street water pressure or well pump and tank pressure settings), and any pressure regulators installed in the piping system, and the effects of any flow rate restriction at the fixture.
   
   Restricting the flow rate actually increases the pressure measurable in the water supply piping system.

Hot Water Quantity Diagnosis & Improvement Articles

As Carson Dunlop Associates ' illustration (left) shows, one way to improve hot quantity in a building is by hooking up more than one water heater, in parallel or in series.

The articles listed below offer more details about steps one can take to increase hot water quantity, pressure, and flow in a building.

Below we list hot water quantity, pressure & flow problem diagnosis, repair, and improvement articles. For each item we describe how the topic pertains to hot water quantity, pressure, or flow complaints.

The list below is in alphabetic order, not in order of priority of things to try.

Diagnosis and repair for hot water temperature and more about hot water pressure are explained separately

at HOT WATER IMPROVEMENTS.

• ALTERNATIVE HOT WATER SOURCES - besides electric, gas, oil, solar, indirect, & range boilers, are alternatives
• ANODES & DIP TUBES on WATER HEATERS discusses hot water tank sacrificial anodes and dip tubes whose problems can produce both sulphur smells, reduced hot water quantity (incoming cold at the wrong place in the tank is rapidly diluting outgoing hot) and even reduced hot water pressure and flow (debris from degraded tube clogs pipes) .
• ANTI_SCALD VALVES & HOT WATER QUANTITY - improve safety and meter hot water more slowly - makes it last longer.
• CLOGGED PIPING & Hot Water Flow - diagnose and correct poor hot water pressure and flow due to pipe clogging
• ELECTRIC WATER HEATERS - suggestions for inspection, diagnosis, repair
• EXTRA TANKS to INCREASE HOT WATER - pre-heat your hot water absorbing ambient building heat or increase hot water quantity with cascaded, staged, multiple water heaters, possibly using more than one energy source
• GAS FIRED WATER HEATERS - suggestions for inspection, diagnosis, repair
• GAS HEATERS, HIGH EFFICIENCY - if replacing a water heater, consider a model that saves money in operating cost
• HOT WATER CIRCULATOR PUMP SPEEDS DELIVERY - hot water pump and loop systems for instant hot water in large buildings. Ways to improve hot water quantity, pressure, and flow are discussed
  beginning
  • HOT WATER IMPROVEMENTS and continuing at
  • HOT WATER QUANTITY IMPROVEMENT and at
  • HOT WATER PRESSURE IMPROVEMENT

Hot Water Usage Efficiency Improvements

Often efficiency improvements in hot water use (or production) include include recommendations for installing restrictions on the flow rate of hot water in a building (flow restrictors or restrictors combined with an anti-scald valve), either right at the fixtures, or at the water heating device.

You are trading off total flow rate for reduced water heating costs.

• Change home appliances and plumbing fixtures
  
   to install devices that consume less hot water. For example, replace showerheads that have a flow rate greater than 2.5 gallons per minute (the current National Energy Policy Act standard), with low flow shower heads.
  
  Watch out: for increased hot water scalding burn risk hazards where low-flow shower heads are installed in homes without an anti-scald device.
  
  See MIXING / ANTI-SCALD VALVE
• How to take an efficient but nice and hot shower
  
  especially for older fixtures that do not make use of a reduced-flow shower head, take shorter showers, and better still, use your shower more intelligently. Our daughter Mara used to start a shower by turning the hot water all the way on, to its fastest flow rate, then tempering the hot by turning on enough cold to avoid getting burned.
  
  This gives a wonderful power, fast, huge water flow out of the shower head.
  
  But if you instead turn the hot water, say just half way on, or fully on until water is hot, then backing it off to half-speed, you will need less cold mixed-in to make the shower comfortable, and you'll suck hot water out of your water heater at half the rate.
• When replacing a clothes washer
  
  install a models that uses less water by installing a high efficiency washing machine with a "low water factor" and always wash full loads rather than smaller loads in your washing machine
• HOT WATER QUANTITY IMPROVEMENT -
  
  this article on improving the quantity of hot water in buildings, includes this list of diagnostic and improvement articles and descriptions (below) of specific things you can do.
• INDIRECT FIRED WATER HEATERS -
  
  allow a larger tank of hot water, heated efficiently by a separate heating boiler. Larger tanks mean more hot water, especially if you are converting from a tankless coil.
• INSULATE HOT WATER PIPING - worth doing where piping is accessible, especially on piping running through cool areas will improve temperature of the hot water where it is delivered.
  
  By losing less heat as hot water moves from the water heater to the fixture, you are obtaining more hot water because you are wasting less heat (and hot water) just to heat up the pipes between the water heater and the fixture.
• INSULATE HOT WATER TANK? -
  
  probably not worth doing except in special cases; important safety warnings suggest not to even try this on modern water heaters.
• LARGER DIAMETER WATER SUPPLY PIPING -
  
  worth doing if you are replacing clogged pipes or building new construction, will increase the flow rate or perceived "pressure" at a plumbing fixture.
  
  This can mean you actually use your hot water up faster, reducing the total hot water quantity available rather than increasing it.
  
  So keep flow rate or "pressure" and quantity separate and clear when thinking about hot water supply.
• MIXING / ANTI-SCALD VALVES -
  
  can not only avoid scalding hot water dangers, but can meter hot water usage to give a longer bathing shower time. The flow rate can be the same (at lower temperature) or may be less, but the total time in the shower before you run out of hot water is increased.
  
  So if "quantity" means "how long can I stay in the shower" rather than "how much shower water can I use", then a mixing valve increases the time in the shower.
• MULTIPLE WATER HEATERS IN PARALLEL
  
  to increase total hot water quantity
• MULTIPLE WATER HEATERS IN SERIES
  
  to stage hot water heating for varying levels of demand
• OIL FIRED WATER HEATERS -
  
  fast recovery water heaters, suggestions for inspection, diagnosis, repair
• RANGE BOILER WATER HEATER
  
  an older form of indirect-fired hot water heating used with separate heating boilers
• SIDE ARM COIL WATER HEATER
  
  similar to instantaneous and tankless coil water heaters, often used with range boilers
• SOLAR HOT WATER HEATERS -
  
  lower energy cost, effective hot water source in sunny climates
• TANKLESS COIL HOT WATER INCREASE -
  
  various tricks can significantly improve the safety and water quantity available
• TANKLESS WATER HEATERS -
  
  no hot water tank tank, no standby losses, just hot instant hot water, at various flow rates
• WATER HEATER TEMPERATURE TOO COLD or TOO HOT
  
  where to look for problems when the "hot water" is not hot enough
• Water heater choices: The characteristics of various water heaters such as life expectancy, cost, safety, and capacity are discussed
  
  at ALTERNATIVE WATER HEATER PROPERTIES
• WATER HEATER SCALE DE-LIMING PROCEDURE
  
  explains how mineral scale build-up in a water heater (or in building water piping) can result in both poor hot water quantity
  
  and WATER HEATER SCALE PREVENTION
  
  explains how to prevent lime and scale formation in water heating equipment
• WATER HEATER SIZE SPECIFICATION & Capacity Charts or Tables
  
  gives advice on choosing the water heating equipment size or capacity in gallons or flow rates for both residential and commercial buildings
  
  For tankless or demand type water heating,
  
  see TANKLESS WATER HEATER SIZE REQUIREMENTS
  
  and see MULTIPLE GANGED TANKLESS WATER HEATERS
• WATER PRESSURE LOSS DIAGNOSIS & REPAIR -
  
  overall guide to improving building water pressure
• WATER SOFTENERS & CONDITIONERS -
  
  how to install and adjust a water softener to avoid hot water piping or tankless coil clogging due to hard water and minerals

Using Extra Tanks to Increase Hot Water Pressure, Flow, and Volume in a Building

As we illustrate with Carson Dunlop Associates' sketch, it is possible to install multiple active water heaters in a parallel design for simple increase in total hot water quantity, or these tanks could have been installed in series, leaving the first or up-stream tank turned off when less hot water need was anticipated.

Leaving a hot water tank turned "off" can still cut water heating costs a bit, as we discuss next.

Passive water pre-warming tank

Use a water tank or hot water tank or old water heater tank installed upstream from water entering the tankless coil (or primary water heating tank, whatever water heating method is used).

Remove insulation from the holding or staging tank. Water sitting in this tank will absorb water from the indoor environment and in most locales will be warmer than water coming directly from a well or municipal water supply.

Often people will simply salvage an old water tank and use it for this purpose. By pre-warming water headed for the tankless coil, the coil itself will not have to raise the water temperature as much as otherwise.

Thus when the occupants are drawing hot water in the building, heat will be drawn out of the heating boiler at the coil at a slower rate - you'll have more domestic hot water.

Active water pre-heating tank

Install a water heater (oil, gas, solar, electric) on the water piping upstream, that is, before water enters the tankless coil (or primary water heating tank, whatever water heating method is used).

This water tank can be left off when there is not much demand for hot water, in which case it will function as a passive water pre-warming tank as we discussed above. When a greater quantity of hot water is going to be needed (say many weekend visitors to a building), turn on the water heater to permit it to "boost" hot water headed for the tankless coil.

As occupants in the building draw hot water out of the system, heat will be drawn from the heating boiler and tankless coil at a very low rate, possibly not at all, until we've exhausted the hot water that was stored in the separate water heater tank.

Some people install this system backwards: hot water is fed from the tankless coil into a water heater tank. This is a much less efficient way to make hot water as all of the water entering the water heater tank will always cause the heating boiler to run. We do not recommend this arrangement.

See our discussion of MULTIPLE WATER HEATERS IN PARALLEL

and also MULTIPLE WATER HEATERS IN SERIES for more details regarding this approach to increasing hot water quantity.

Insulate Hot Water Supply Piping

Be sure that the hot water supply piping in the building has been insulated throughout its run.

In our photo at left our client is pointing out that foam insulation applied over the hot water pipe leaving the water heater was placed too close to the water heater draft hood. Spillage at the draft hood was melting the water pipe insulation - indicating an unsafe flue gas spillage problem.

The length of hot water supply pipe running between the building hot water source and the building faucet or fixture where hot water is being delivered will affect the temperature of water received there.

A long run of un-insulated hot water pipe will deliver cooler water than a well-insulated water supply pipe of any length.

The reason that insulation on hot water piping increases the total hot water quantity (and temperature) is that the hot water is not giving up so much of its heat in the form of radiant losses during movement of hot water from the water tank to the destination plumbing fixture.

The foam insulation on hot water lines (or hot water heating pipes) in our photo at left is readily available at building supply stores.

This foam pipe insulation is purchased according to the diameter of the pipe it is going to cover. In residential applications that's usually 1/2" pipe or 3/4" copper or galvanized steel pipe. The insulation is split so that it can be simply pushed onto the pipe that is to be insulated.

We insulate hot water piping to minimize heat loss between the heater and the point of use.

We also like to insulate cold water piping in order to reduce condensation and dripping off of the cold water lines during warm humid weather.

Also see our advice and safety warnings about water tank insulation

at INSULATE HOT WATER TANK?.

Install Larger Diameter Water Supply Piping to Improve Hot Water Pressure & Flow

As we discussed at WATER PIPE CLOG REPAIR, and as we illustrate with Carson Dunlop Associates' sketch shown here, installing larger diameter water supply piping makes a large difference in the water flow rate.

In fact you can improve hot water flow in a building by replacing only part of the supply piping - perhaps that portion which is easily accessible. Installing larger water supply piping feeding the water heater may alone improve the hot water pressure and flow in the building.

Watch out:  if your hot water is provided by a tankless coil, increasing water pipe diameter may not be of much use, and it could make matters worse!

A tankless coil (and also an instantaneous water heater) is normally rated by its manufacturer as capable of increasing water temperature to a desired level only if water flow through the coil is limited to a specific rate, perhaps 5 gpm. Flowing water through the tankless coil or instantaneous water heater too fast will mean that the water temperature may be too low at the fixture.

In sum, larger diameter piping increases water pressure and flow. It does not increase the total volume of hot water that is available from a water heater. This improvement may be of most value where water pressure is poor and where water piping has previously become clogged by rust or mineral deposits.

You may regain some of this loss by insulating hot water supply piping or by setting water heater or boiler temperatures higher as well as by an adjustment at

the HOT WATER MIXING VALVE.

See complete details of this topic

at WATER SUPPLY PIPE DIAMETER vs FLOW

Water Heater Size Requirements & Specifications

How to determine the size of water heating equipment needed for a residential or commercial building. This topic has been moved to a separte article found

at WATER HEATER SIZE SPECIFICATION

For tankless or demand type water heating (where hot water quantity is "infinite" as long as the incoming water temperature and flow rate are within limits of the heater)

see TANKLESS WATER HEATER SIZE REQUIREMENTS

and see MULTIPLE GANGED TANKLESS WATER HEATERS for another way to increase total hot water delivery capacity at a building.

Don't Confuse Hot Water Quantity with Hot Water Pressure or Flow Rate

Hot water pressure that you should consider as a "force" is measured in psi or if you are in a country that uses SI units of measurement, water pressure is measured in Pascals (Pa) where 1 pascal = 1 newton per square metre (N/mM²)

Hot water flow rate that you should consider as a "rate" or quantity in gallons or liters per minute, is measured in gpm or lpm.

When most people complain of weak water "pressure" they are talking about a too-low water flow rate.

Weak water "pressure" when we really mean a lousy or dribbling volume of water coming out of a shower head or sink or tub faucet is affected by the incoming water pressure and by the pipe size or diameter and by the height to which water has to be lifted from its source.

Details are at

• CLOGGED SUPPLY PIPES, DIAGNOSIS
• HOT WATER PRESSURE IMPROVEMENT
• HOT WATER QUANTITY IMPROVEMENT
• WATER FLOW RATE CALCULATE or MEASURE
• WATER PRESSURE MEASUREMENT
• WATER SUPPLY PIPE DIAMETER vs FLOW
  

 

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Where is the on-off switch on a water heater?

Where on the water heater do you get the hot water-is there a button or something you can turn on? - On 2016-12-28 by Sandy smith -

Reply by (mod) -

Sandy:

If your water heater is electric there will be one or two adjustable thermostats behind access covers on the heater - watch out: touching live electrical components in there can kill you.

If your water heater is gas-fired the temperature setting is usually on the gas control.

If your water heater is an oil fired unit the temperature setting is on the aquastat or limit control.

Watch out: setting temperatures too high risks scalding burns. Search InspectApedia.com for ANTI SCALD VALVES to read more details.

Search InspectApedia.com for MORE HOT WATER to see other ways to improve the amount or temperature of your hot water.

How do I know how much hot water is in the water heater & how hot it is?

Is there a device for telling how hot the hot water is in your hot water tank and also how much water there is, or is the 2nd part a function of the first based upon volume? - On 2016-05-23 by Andrew Barnes -

Reply by (mod) -

1 measure water temp at the tap

2 Infra Red scan pipe temp anywhere enroute

3 install an in line temp gauge at the water tank hot water line above the tank

4 some tanks may have an extra tank top tapping where a gauge can be installed

...

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

Or see these

Recommended Articles

• HOT WATER IMPROVEMENTS - home
  • ALTERNATIVE HOT WATER SOURCES
  • ELECTRIC WATER HEATER ELEMENT TESTS
  • GAS HEATERS, HIGH EFFICIENCY
  • HOT WATER CIRCULATOR PUMP SPEEDS DELIVERY
  • HOT WATER EFFICIENCY IMPROVEMENT
  • HOT WATER PRESSURE IMPROVEMENT
  • HOT WATER PRESSURE LOSS
  • HOT WATER QUANTITY IMPROVEMENT
  • INSULATE HOT WATER TANK?
  • MULTIPLE GANGED TANKLESS WATER HEATERS
  • TANKLESS WATER HEATERS
  • WATER CONSERVATION MEASURES
  • WATER HEATER COMPARISONS, PROPERTIES
  • WATER HEATER PIPING
  • WATER HEATER PROBLEM DIAGNOSIS
  • WATER HEATER SIZE SPECIFICATION
  • WATER HEATER STANDBY LOSSES
  • WATER HEATER TEMPERATURE TOO COLD or TOO HOT

Suggested citation for this web page

HOT WATER QUANTITY IMPROVEMENT at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER HEATERS

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