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AGE of WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
ANODES & DIP TUBES on WATER HEATERS
ANTI SCALD VALVES
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions
BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTER, HEATER WATER FEEDER
CARBON MONOXIDE - CO
CHECK VALVES, WATER SUPPLY
CLOGGED SUPPLY PIPING
CROSS CONNECTIONS, PLUMBING
DEBRIS in WATER SUPPLY, Water Heater
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
FLOODED WATER HEATER REPAIR
FREEZE-PROOF A BUILDING
GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HEATING COST SAVINGS METHODS
HOT WATER SUPPLY
HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER EFFICIENCY IMPROVEMENT
HOT WATER PRESSURE EXPANSION RATE
HOT WATER PRESSURE LOSS
HOT WATER PROBLEM DIAGNOSIS
HOT WATER QUANTITY IMPROVEMENT
HYDROGEN SULFIDE GAS
INDIRECT FIRED WATER HEATERS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
NO HEAT - NO HOT WATER: HEATER DIAGNOSIS
NOISE, WATER HEATER
ODORS IN WATER
PIPING IN buildings, Clogs Leaks Types
RELIEF VALVE LEAKS
RELIEF VALVES - Water Heaters
SCALE REMOVAL, WATER HEATERS
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
TANKLESS WATER HEATERS
THERMAL EXPANSION of HOT WATER
THERMOSTATS, WATER HEATER
TIMERS for ELECTRIC WATER HEATERS
WATER HEATER ALTERNATIVES
WATER HEATER ANODES, DIP TUBES
WATER HEATER AIR INLET
WATER HEATER DEBRIS FLUSH
WATER HEATER DRAIN PROCEDURE
WATER HEATER EFFICIENCY
WATER HEATER FLUSH PROCEDURE
WATER HEATER NOISES
WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER PROPERTIES
WATER HEATER SCALE
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE TOO HIGH: DANGERS
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
This article explains how to improve the hot water pressure or temperature in a building. We list decribe detailed procedures for diagnosing and fixing the various causes of either hot water that is too weak in flow (bad pressure) or hot water that is not hot enough.
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Thanks to Carson Dunlop, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
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.
These Articles Describe the Diagnosis & Repair Steps to Increase Hot Water Pressure or Temperature
As Carson Dunlop Associates' illustration (left) shows, one way to improve hot water flow in a building is by a larger diameter cold water pipe supplying the hot water heater.
Below we list hot water pressure or temperature diagnosis, repair, and improvement articles. For each item we describe how that topic pertains to hot water temperature and flow.
The list below is in alphabetic order, not in order of priority of things to try. Diagnosis and repair for hot water quantity are explained separately at HOT WATER QUANTITY IMPROVEMENT. Please Contact Us if you think we should re-order or add to this list.
The topics discussed in this article address improving hot water flow and improving hot water total quantity.
How to Increase Hot Water Quantity & Flow When a Tankless Coil is Installed - how to avoid running out of hot water
A tankless coil used to produce hot water is shown in the sketch at the top of this page and again in the photograph at left. The black rectangle is the mounting plate that bolts the tankless coil to the heating boiler - in this case it happens to be a steam boiler.
On this tankless coil cold water enters at the lower of the two pipes connected to the coil. You'll also see that the cold water line continues to enter the bottom of the anti-scald valve.
The hot water leaves this tankless coil from the upper pipe connected to the coil, where it flows down to enter the mixing valve (tempering valve) at the left side of that valve (see the black temperature setting knob on top of the valve?). We discuss anti-scald valve or tempering valves in detail just below.
Tempered hot water (mixed hot and cold) leaves at the right side of the mixing valve and heads for the plumbing fixtures in the building.
On many heating boilers the tankless coil mounting plate is round, not rectangular, and it may be located on the top of the heating boiler as well as on the front, back, or either side of the heater.
Use a flow limiter to increase the length of time that you can run the hot water and to increase hot water temperature
Tankless coils do not provide infinite hot water. Cool water entering the coil draws heat out of the boiler water and into the house water. The oil or gas burner that reheats the heating boiler cannot pump heat into the boiler as fast as the tankless coil is removing heat. That's because water is entering the coil at 40 to 55 deg F in most cases, and it's trying to leave at the boiler temperature that may be close to 200 degF.
So if you run water too fast through the tankless coil it'll draw heat out of the boiler quickly and you'll have great hot water pressure, but not for very long. Then you'll just have tepid or cold water pressure. Some tankless coils have a flow limiting valve mounted right at the coil to prevent water from flowing through the coil too fast.
Using a flow limiting valve on a tankless coil lets you run the hot water longer before you run out by forcing you to run it more slowly.
Use of a flow limiting valve, because it slows the passage of cold water through the water heater, will also permit the water to arrive at the plumbing fixture at a higher temperature - the hot water will be hotter.
Intelligent use of shower controls to restrict hot water flow can save hot water costs and provide longer shower bathing time
Even when a flow limiter is not installed in hot water piping, a bather can save on hot water heating costs by smart use of shower controls. Some bathers turn the hot water all the way to it's fastest flow position, followed by turning on lots of cold water in order to avoid being scalded. Instead of this fastest-flow best water pressure approach, turn the hot water to a less powerful stream, which will require also turning on less cold water to obtain a comfortable shower temperature.
This method of bathing does not really provide a greater quantity of hot water in a building, but by drawing hot water out of the water heater more slowly, one can either have longer time in the shower, or subsequent bathers can have adequate hot water at less total water heating cost.
The use of a mixing valve or anti-scald valve at a tankless coil permits us to set the Honeywell 6006 limit control switch or other boiler temperature or water heater temperature limit control to a higher number without having to worry about scalding occupants of the building.
Keeping the water at a higher temperature inside the heating boiler (with a tankless coil system) or in the water heater (with a separate domestic water heater or indirect-fired water heater system) means that there is more heat stored inside the heating boiler or water heater.
By adding cold water to the very hot water leaving the tankless coil or water heater, we draw hot water out of the water heater itself more slowly than we would without this addition.
Therefore we can expect to draw a larger quantity of (tempered) hot water from the tankless coil on such a system than otherwise. We will have more total domestic hot water for washing and bathing, and we have safer hot water (non-scalding) than if we omitted this pair of controls.
See MIXING / ANTI-SCALD VALVES for a detailed discussion of how to install, set, and use mixing valves, anti-scald valves, or tempering valves on water heating systems to avoid scalding burns and to improve hot water heater performance.
Hot water pressure and hot water flow in a building may be poor even where a mixing valve has been installed. This condition could be due to poor overall building water pressure or due to clogged pipes.
If cold water pressure is good and hot water pressure is poor, the problem is not an overall building water pressure issue. There is a problem with the hot water system that needs to be found and corrected.
If hot water pressure is strong when the water is first turned on but flow quickly falls off to a weak hot water stream, it's likely that the hot water piping (or tankless coil) are clogged.
Often this repair involves using acid to try to remove minerals that are clogging hot water system piping or a tankless coil, or the tankless coil may need replacement.
Abandoning a tankless coil altogether: When we bought our house the tankless coil was almost totally clogged with minerals, and we figured that it wouldn't provide enough hot water anyway, so we abandoned it. In the photo at left you can see the round black tankless coil face, with two holes - where we removed the cold-water-in and hot-water-out pipes and simply abandoned the tankless coil. A separate water heater was installed in our utility area. (We'd have preferred an indirect-fired water heater which is discussed later in this article but that's not what we got.)
See TANKLESS COILS for an explanation of how these water heaters work and why they clog up and how to stop clogging up the coil.
See WATER PIPE CLOG REPAIR for a discussion of loss of water pressure due to clogged piping or clogged tankless coils.
At Larger Diameter Water Supply Piping we discuss the benefits of using larger diameter water supply piping both to improve water pressure and flow and also to delay the clogging of pipes due to minerals or rust
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