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water pipes banging

when we open the cold water the pipes make some banging noise as the water runs. stops when is turn-off.
what could this be?.

Re: water pipes banging

This is known as "water hammer" and is usually caused by one of several factors.

One factor could be excessive water pressure coming into the house, or if you have well water, from a water pressure pump in the cellar that is set too high.

Another factor, if the noise is associated with only one faucet, the washer inside that particular faucet may be damaged or loose & is fluttering, causing a hammer sound.

If you're getting banging from ALL the faucets when turned on, then read on.

There are usually short lengths of pipe filled with air here & there (water cushions) on the water supply piping that act as cushioning when a water faucet is suddenly turned off; this cushions the blow of the water pressure hitting the back inside of the faucet, when the faucet is suddenly turned off.

These air filled water cushions over time often get filled with water (waterlogged) instead of air & thus lose their cushioning function.

Other piping systems have air-filled water arrestor fixtures placed here and there that do the same thing.

Another factor is that the pipe holdown straps & clamps come loose behind the walls or in the cellar & then start to bang against the wood floor joists or other supports; check this first & tighten any loose clamps

The sites below treat all of these possibilities.

Get a helper who can turn the faucets on & off while you check the basement, under kitchen & bath cabinets, etc. until you locate the source of the noise.

You should have your water pressure checked by a plumber or handyman, especially if the less costly remedies don't solve the problem.

If you're handy, you can buy a psi gauge ($5) at Home Depot/Lowe's (& a copper adapter if necessary) and screw it onto the outside faucet, a faucet aerator or the waste vent of an on/off valve.

Standard water pressure for a residence is ~50-65 psi.

If it's considerably above this figure, either the pump pressure is out of adjustment (well water) or the city supply is too high & you need a pressure reducing valve installed on the incoming line.

But first concentrate on finding any loose holdown clamps & retighten them; then try to locate any waterlogged air chambers or water hammer arrestors.

Shut off the main water supply & drain the system; there is usually a waste vent on the side of one of the lower on/off valves, or you can open the outside faucet; many times, this is all that's needed to re-establish air in the hammer arrestors or air chambers.

The water hammer arrestors (if present in your system) usually have a little air vent valve at the top that can be temporarily opened that will let in air once you shut off the main water supply valve in the basement, drain the system (to let air back into the air chamber/arrestors),re-close the little valve on the water arrestors, then reopen the main water valve to see if the water hammer has gone away.

Water Hammer arrestors are available at the big box stores; if you're handy, you can make up a few by soldering some short lengths of pipe with a cap.

There are 1/2" copper/brass elbow fittings ($3) that have a 1/8" threaded tap for a bleeder valve ($1).

Thus, you can make up your own water hammer arrestor for ~$5 if you can solder copper tubing.



Re: water pipes banging

make sure all your shut off valves are fully open,check under your sinks and toilet,a 1/2 open valve can cause this as a loose washer will "flutter"as the water passes by

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