"Understanding Your Home" by Building Inspector Mark Visser
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INSTALL PRESSURE CHAMBERS
A pressure chamber is 12-18" (30-46 cm) vertical piece of copper pipe on a T-fitting with a cap on the end. It would not take too long for a handy person to install one. The air filled pipe will trap air which compresses when the shock wave hits. The air acts as a shock absorber.
The drawback of pressure chambers is that eventually air and water will mix and the system has to be drained to restore the air pockets.

HOW TO RECHARGE PRESSURE CHAMBERS WITH "FRESH" AIR
1. Turn off the water supply at the water meter.
2. Starting at the highest level, open all taps, flush all toilets and turn off water supply to the water heater.
3. The system is drained when no more water is discharged from the lowest tap.
4. Close all taps.
5. Turn on water supply at the water meter. Turn on water supply to water heater.

This pressure chamber will help to control water hammer but has limitations, see text above.


Water Hammer
(can happen when a valve or faucet is suddenly closed)





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WHAT IS WATER HAMMER?
Water hammer is something that happens within the floor and/or walls. It is a loud noise like as if someone is hitting the plumbing pipes in a rapid fashion with a metal object. The banging or tapping noise can be heard throughout the house.
There are two reasons for water hammer to occur. One is the quick closing of the electric solenoid valve on clothes washing machines and dishwashers. The other reason could be plumbing pipes (hot and cold supply pipes) that are not properly supported.
When a solenoid valve, or any other tap in the house, is suddenly closed the water in the supply line comes to an sudden stop. This sudden stop results in a spike of pressure, causing pipes to rattle and shake. The force can rattle loose pipes which can bang against studs and joists. You can see this force in action by quickly opening and closing the nozzle on your garden hose. It will move around by the sudden change in water pressure.
Unless you remedy the situation, water hammer will get worse and can cause leaks.

HOW TO FIX WATER HAMMER
- Refasten loose pipes, add more support
- Install pressure chambers
- Install water hammer arrester
- Lower the water pressure

REFASTEN LOOSE PIPES, ADD MORE SUPPORT
This job would be an easy one if you live in a bungalow with an unfinished ceiling in the basement. For all other type of homes refastening pipes and adding more pipe hangers may not always be possible because most of the water supply lines are hidden in walls and in ceiling/floor cavities.

Water hammer arrester for
inline installation		 Water hammer arrester for
toilets, sink, dishwasher 		Water hammer arrester for
washing machine hose






INSTALL WATER HAMMER ARRESTER
- What is a water hammer arrester?
- Where should the arrester be installed?
WHAT IS A WATER HAMMER ARRESTER?
A water hammer arrester is a device that does the same thing as a pressure chamber. It provides an air cushion to absorb the shock caused by the quick closing of the electric solenoid valve on clothes washing machines and dishwashers or any other tap. Unlike the pressure chamber, a water hammer arrester does not has to be recharged as the unit is permanently sealed. Once installed the wall or ceiling can be closed up again. There are special arresters to accommodate water supply hoses to the washing machine.
WHERE SHOULD THE WATER HAMMER ARRESTER BE INSTALLED?
The arrester should be installed on the pressure side of the solenoid valve that is causing the problem. For the dishwasher you need one arrester for the hot water supply and one each for the hot and cold water supply to the the washing machine.
Properly sized and installed, water hammer arresters will eliminate the shock and noise called "water hammer."

LOWERING THE WATER PRESSURE
If there is water hammer at all the taps in your home the water pressure may be too high. Overall water pressure in the plumbing supply system can be reduced by installing a reducing valve in the water main, on the house side of the water meter. Sometimes lowering the water pressure may not be feasible because it lowers the pressure for proper operation on upper floor faucets when one is open on the main floor.
Water pressure varies widely. On a well system, the normal pressure is 30 to 60 psi, City water pressure is normally 50 to 75 psi.

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