Water Supply Noise due to Thermal Expansion?


I have a plumbing issue that I'm looking for suggestions on. After using a substantial amount of hot water (say, a long shower + washing laundry) I will hear a loud rumbling / vibrating sound throughout the house, emanating from the water pipes. The noise seems to originate from the pressure regulator on the main water supply. If I open a hot water tap while the noise is occurring it will immediately stop. (The meters show that no water is flowing while the noise is occurring.)

I suspect that thermal expansion of hot water is causing backpressure on the regulator, and the noise is vibration as the seals in the regulator have water pushed past them.

My current plan is to get a pressure gauge and replicate the issue by nearly-emptying the hot water tank and letting it fill and heat. This should allow me to see the pressure swing in the system. Then based on what I see for the low and high pressures, consider the following options:

Decrease overall water pressure in...
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Start Up Conditions



Water supply systems may, because of such events as high line

pressure, frequent cut-offs, the effects of water hammer among

others, have installed devices such as pressure reducing valves,

check valves, back flowpreventers, etc...to control these types of

problems. When these devices are not equipped with an internal

by-pass, and no other measures are taken, the devices cause the

water system to be closed. As water is heated, it expands (ther-

mal expansion) and closed systems do not allow for the expan-

sion of heated water.

The water within the water heater tank expands as it is heated and

increases the pressure of the water system. If the relieving point of

the water heater's temperature-pressure

relief valve is reached, the

valve will relieve the excess pressure. The...

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General Information - What is Thermal Expansion?

When water is heated it expands. For example, water heated from 90°F to a thermostat setting of 140°F in a 40 gallon hot water heater will expand by almost one-half gallon. This is because when water is heated, its density decreases and its volume expands (see below). Since water is not compressible, the extra volume created by expansion must go someplace. During no-flow periods in a system, pressure reducing valves, backflow preventers, and other one-way valves are closed, thus eliminating a path for expanded water to flow back to the system supply. Hence, system pressure increases.

Temperature vs Density

Thermal expansion of water in a closed plumbing system can create a number of annoying and potentially dangerous problems. These include: the build up of unusually high pressure in a system (even when a pressure reducing valve is installed); pressure surges; and the chronic or...

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A standard tank water heater can stress your plumbing pipes by the normal thermal expansion that happens during the heating process. A safety device known as a water heater expansion tank (sometimes called a thermal expansion tank) can help minimize the risk of pressure damage to the plumbing system. (This is normally not a problem on modern on-demand, tankless water heaters--only tank-style heaters are subject to this problem.)

The water heater expansion tank serves as an overflow receptacle by absorbing excess water volume created by the tank water heater when heating water, as well as absorbing fluctuations in the incoming water supply pressure. Since water expands when it is heated due to thermal expansion, the water heater creates extra water volume every time it heats water. It's estimated, for example, that the cold water in a standard 50-gallon water heater expands to 52 gallons when heated to 120°F. This extra water volume can create excess pressure in the plumbing...

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This page was originally created by ShneekeyTheLost. Other contributors can be found on the credits page.

For version 3+ of Thermal Expansion (Minecraft 1.6.4 and above), please view Getting Started (Thermal Expansion 3).

Thermal Expansion for Newbies[edit | edit source]

(A reference guide for the rest of us)

So, first off, what does this mod do?[edit | edit source]

It brings your production to the industrial age, with machines that smelt more efficienlty and returns more output on ores! It also revolutionizes your Minecraft Joule (MJ) Power System. More on this later. It also has machines which provide utility; these can either be ease of use or lag-reducing techniques.

Why might you want to use this mod?[edit | edit source]

You can't find a rubber tree among all the extra biomes around your immediate spawn, and you want to get your industrial setup going anyways. You want to get started with another mod, and there's a machine which requires a...
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Thermal Expansion

Code Requirements on Thermal Expansion Control in Domestic Service Water Heating Systems

by Dennis M. Streit

When dual-check valves and check valves are installed in water meters, they seal off the household plumbing system from the potable contaminated household water into the public supply. Because they do their job so well, these backflow devices can contribute to thermal expansion, which can cause serious problems.

Typical Water Heating System

In a typical domestic water supply system some water is used in the cold water service lines. Some water may be used in a secondary 'closed' piping system, sealed from the potable plumbing system, which connects to a hot water boiler. This piping system is usually filled up once and the water is used over and over, only as a medium to convey heat.

The largest use of potable water in the home is usually for hot water for bathing, washing and dish washing. Water in the...

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Condensate Drain

The water heaters covered in this manual are condensing appliances and require a building drain to be located in close proximity to allow the condensate to drain safely.

Condensate drains from the water heater at the exhaust elbow located at the bottom. The field installed condensate drain line must not be elevated above the condensate drain connection on the condensate trap, see Figure 9. If the condensate does not drain properly it will build up in the exhaust (vent) elbow. This will restrict the flow of flue gases and cause the Blocked Exhaust pressure switch to open its contacts. The control system monitors all pressure switches, if the Blocked Exhaust Switch contacts are open the control system will lock out and disable heating operation. The “Blocked Exhaust” Fault message will be displayed on the control system’s LCD, see Fault And Alert Conditions beginning on page 61.

Note: If the “Blocked Exhaust “ Fault message is ever displayed on...

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In Construction


Effect of Thermal Expansion on Various Materials

Fragile Materials

Thermal Expansion Applications


Other Examples


Thermal Expansion Coefficient of Common Materials


Pavement control joints (thin), and expansion joints (thick). Control and expansion joints are often confused but they are not the same, as you can see in this photograph. Control joints are cuts at periodic intervals on the pavement. They prevent irregular cracking due to thermal expansion by being the artificial “cracks”. They are often filled with an elastic sealant such as silicone, tar, or rubber.

As temperature changes, so does the volume of matter — this property is called thermal expansion. In practical terms, when building roads, houses, and machines that have sufficiently large components and that are subject to a wide range of temperatures, it is important...

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Hot water heater expansion tanks

The addition of a hot water heater expansion tank can both resolve and prevent high water pressure. If either undetected or unresolved, excessive pressure can seriously compromise the durability, performance and the efficiency of the system.

Inspecting for high pressure is an important water heater maintenance procedure that should be performed periodically. A storage tank with pressure that exceeds 80 psi (pressure per square inch) when the heating element is on and hot water is not in use will require an expansion tank in most cases.

With that said, storage tanks that don't experience high water pressure stand to benefit as well. Before installing an expansion tank consider the following;

Warning - High Water Pressure and Gas Powered Storage Tanks

Overtime excessive pressure can become a serious safety concern in gas water heating tanks. High water pressure can ultimately compromise, or even...

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Why the relief valve leaks: thermal expansion of hot water

This article explains hot water thermal expansion that can cause leaks, drips, or discharges from pressure relief valves, temperature/pressure relief valves, or TP valves found on heating boilers, water heaters.

We explain how to find and fix leaky relief valves on hot water heating systems.

Watch out: a dripping or frequently spilling T&P valve is dangerous because those very leaks can eventually cause the valve to clog and then to fail to open when it should.

Green links show where you are. © Copyright 2017 InspectApedia.com, All Rights Reserved.

Closed Hot Water Systems & Thermal Expansion Problems - Why is the Water Heater Relief Valve Leaking?

Watts and other manufacturers of TP valves warn of serious safety hazards caused by...

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