Sketch of a tankless coil tempering valve or anti scald valve Carson Dunlop Associates How to Get More Hot Water
How to get more hot water or hotter hot water from any type of water heater

  • HOT WATER IMPROVEMENTS - CONTENTS: How to improve hot water pressure , flow rate, & how to improve hot water temperature - How to stop running out of hot water, How to make hot water hot enougg;
  • POST a QUESTION or READ FAQs about improving hot water pressure or temperature in building water heater systems

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Hot water supply improvement guide:

This article explains how to improve the hot water pressure or temperature in a building.

We list and decribe detailed procedures for diagnosing and fixing the various causes of running out of hot water, hot water that is too weak in flow (bad pressure), hot water that is not hot enough (temperature too low), and other water heating problems such as water heater efficiency, noises, odors, or contamination.

Topics discussed include comparison of alternative water heating methods, costs, capacities, recovery rates, & safety; Mixing valves - anti-scald valves on heating boilers, tankless coils, & water heaters, how they work; Smart use of shower controls to save hot water heating costs; How an anti-scald valve can increase the total amount of hot water obtained from a tankless-coil hot water system.

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How do we Improve the Domestic Hot Water Pressure or Temperature?

Larger pipes for more hot water (C) Carson Dunlop AssociatesThis article summarizes all of the ways you may want to improve hot water systems at a building, including hot water quantity (stop running out), hot water pressure (flow is too weak), hot water heater efficiency (stop wasting money), and other building hot water supply problems and aggravations.

We start with a description of how to get more hot water when using a tankless coil on a heating boiler to get domestic hot water for washing and bathing.

In a list of articles at this website we then provide links to detailed diagnostic procedures for each type of hot water supply issue.

Before you start fixing or buying stuff to fix a hot water problem hot water problems, you might want to check there to be sure you're fixing the right problem.

Diagnostic guides for all kinds of hot water troubles are summarized at WATER HEATER PROBLEM DIAGNOSIS.

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

Tankless coil on a steam boilerA 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.

Use an anti-scald valve to increase hot water quantity and protect from hot water burns

Photo of an anti-scald tempering valveWhy does an Anti-Scald Valve, mixing valve, or tempering valve on a tankless coil hot water system increases the total amount of hot water available?

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.

Check for and Correct Clogged Piping or Clogged Tankless Coil to Improve Hot Water Pressure or Flow

Abandoned tankless coilHot 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

These Articles Describe the Diagnosis & Repair Steps to Increase Hot Water Pressure or Temperature

Have you already checked our Hot Water Trouble Diagnostic Guide?

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.


Continue reading at HOT WATER QUANTITY IMPROVEMENT or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see these

Hot Water Quantity & Flow Improvement Articles

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