as part of a little basement remodel I’m going to be stubbing some water lines out from the existing copper for a new sink. this is a secondary building – part of a bed and breakfast – with water supplied via 1″ poly line from the main residence. well line and pressure tank in the main residence. cold water line in the secondary building goes about 20′ through a finished soffit in the basement and is evidently poorly fastened in that soffit area. homeowner says guests report – and he has witnessed periodic banging of that water line, probably when a fixture somewhere in the building is turned off. he wants the banging pipes remedied.
it would be great to come up with a fix that doesn’t involve tearing open the soffit to refasten the pipe. I suggested trying a small expansion tank as a shock absorber on the copper line before it disappears into the soffit. my questions are:
1) is a small hydronic bladder-type expansion tank a good device for this or would the old style hammer arrestor (a deadend vertical copper pipe that traps some air) a better approach for some reason?
2) if a bladder tank, can anyone suggest what sort of air pressure in the tank would be best at absorbing shocks. I believe the well pressure varies from 30 to 50psi.
thanks!
Replies
Just saw a fix for that at HD today. Copper with a (gizmo) expansion sleeve on it. Seemed like you could just cut and sweat it into the existing pipeing.
Is it a single Bang, maybe followed by a rattle or two.
Or, when it happens is there a continous bang, bang, bang, or maybe a machine gun sound.
Those can be caused by two different things and have different fixes.
And is anything with solenoid valve on it such as a washer or dishwasher?
William the Geezer, the sequel to Billy the Kid - Shoe
good question! and though I haven't heard it firsthand, the owner reports more of a single bang and rattle than the chattering of a nearly closed valve.whadya think of a bladder tank and if so what's a good air pressure?
That is water hammer do to a quickly closed valve.Some of the newer "washerless" facuets can cause that be that have some like a 120 movement that you can quickly do with your hand.And so can toilet fill valves.There are several styles of hammer arrestors. One is a some sealed cyclinder. I have seen them at the home horror stores. They come all kinds of fittings. Screw on, solder, comression, etc and single end or tees.The other is a small bladder like you describe.http://www.plumbingsupply.com/waterhammerarresters.htmlhttp://www.drillspot.com/products/69519/Watts_150A_Water_Hammer_ArrestorI am not sure, but I think with the bladder type you want the pressure to be equal to the minimum system pressure.BUT, to be effective they need to be installed near the valves. The closer the better..
William the Geezer, the sequel to Billy the Kid - Shoe
gracias.
There are shock absorbers that are miniature versions of the expansion tank -- no bigger than the air-filled stub but they don't become waterlogged.
If they can pinpoint the fixture that is causing the banging I would recommend using a water hammer arrester installed nearest the fixture. I had this issue with my washing machine and you could hear it throughout the house. I used a water hammer arrester made by Souix Chief installed on the back of the washer and it works well. They make arresters for all types of fixtures.
Had a serious problem like this in the 14 story hi-rise I worked in for 12 years in down town Portland.OR. A 2.5 gallon expansion tank solved a serious water hammer problem that the Sioux brand copper arrestors could not handle. Try as best you can to install the expansion tank straight in line at the end of a pipe run-no 90 degree elbows that will only reflect the shock waves back into the system. I let off some of the precharge so it would be less than the line pressure but close. You don't want to compress the bladder too much which will lessen its shock absorbing ability. The schrader air inlet valve will allow you to fine tune your installation if need be. My installation consisted of a 2.5 gal tank with a "T" fitting right on top of the tank. The supply fed directly into the tank port and the connection for the faucet came off the side of the "T". That way the shock wave "looked straight at the bladder." It worked far better than even the plumbing contractors expert predicted. There are great info sources on the internet-Wikapedia, if I remember right.
Dave