Thread: a couple of questions from the new home inspector

how do you fix water hammer? is it just in the venting? and the second question, do you have to have a gas shut off in the house??

thanks for any input.

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If you have water hammer, you usually have good water flow, which is a good thing. To prevent water hammer in an existing home, you can decrease the flow rate (not desireable) or install one or more dampeners. Dampeners can be bought, but you can just as easily make one. It is nothing but a piece of pipe capped on the end and installed vertically (with the capped end up) on the water pipes. Air will be trapped in this dampener and will "absorb" the shock created when the water flow is abbruplty stopped.

Water, like all fluids, is not compressible. You can put it under pressure, but can not compress it. When a valve is closed at the end of a run of plumbing the water in the pipe thinks that it is still going to be moving and continues to try to flow in that direction. The higher the water flow, the faster the water wants to continue moving. Since it is not compressible, it shakes the pipes as the molecules run into each other at the end of the run. This can damage the piping over time. Adding dampeners (filled with air that is compressible) gives the water somewhere to go and softens the blow at the end of the line.

Welcome to the board, by the way.

Water Hammer | Builders Websource®

There should be a main shutoff at the meter it does not have to be in the house. Also each appliance should have a shutoff. If I remember correctly the exception is a Range.

Kevin,

Check the fixture shut off where the sounds of water hammering is coming from to make sure it is opened all the way.

Originally Posted by David Banks

...Also each appliance should have a shutoff. If I remember correctly the exception is a Range.

David - Are you thinking of sediment traps, maybe? I see no exception for ranges in the IRC.

Originally Posted by John Arnold

David - Are you thinking of sediment traps, maybe? I see no exception for ranges in the IRC.

No I was not thinking sediment traps but I may be wrong. I can not find it anywhere but I thought I read it somewhere. Then again I am in Allergy hell right now.

There may be several problems going on at the same time.

There may be a anti-water hammer chamber already installed, and, if the old fashioned type, and if it worked for many years, it may have become waterlogged. Without air in it to compress, it is no longer effective. Those can usually be 'repaired' by simply draining the supply system of water and letting the water drain down out of the anti-water hammer chamber.

There may be loose piping (how many times do we find piping properly secured at the proper maximum spacing intervals?). If this is the case, then tracing down the loose pipe, and the loose section of that pipe, cutting the wall open, securing the pipe, then repairing everything back so it looks nice.

If this problem has always been there, then it may be a combination of no, or insufficient, anti-water hammer chambers and loose piping.

Adding additional anti-water hammer chambers may soften the pressure blows enough to compensate for loose piping, allowing the water hammer to stop.

Originally Posted by David Banks

...I am in Allergy hell right now.

I am in allergy purgatory. Claritin is useless. Zyrtec keeps me out of hell.
Our vehicles are covered in yellow pollen every morning.

Originally Posted by John Arnold

Claritin is useless. Zyrtec keeps me out of hell.

Neither does me much good (not noticeable anyway). Which is why I still get allergy shots (one in each arm) every couple of weeks.

I have heard that water hammer could also be caused by under sized pipes. Is there any truth to that?

Originally Posted by Richard Stanley

I have heard that water hammer could also be caused by under sized pipes. Is there any truth to that?

This from the link I posted earlier.

Improperly sized supply lines for given peak water flow velocity;
Excessive system water pressure and lack of pressure-reducing apparatus;
Inadequate strapping or securing of plumbing to structure;
Excessively long straight runs with no bends;
Lack of expansion tank or other dampening system, such as water hammer arresters;

He didn't specify domestic hot water or heating water/steam. David's post is a good start since it makes it clear that there are multiple potential causes. It's like asking the mechanic what's wrong with my car when it won't start.

Hey Fellas,

the question on the water hammer is likely from one or more of the following, DW, ice maker or AW. Each can have an arrestor installed at the connection or inline and help to alleviate the problem.

thanks to everyone!! it is happening in a wall, best i can gather, when the downstairs shower is turned off.

Hate to say it but it sounds like the plumber didn't install any strapping / brackets. Bummer, but likely the fix, if accessible is to block the piping at the closest area to pull it to a wall and hopefully secure it. Otherwise "I'm Going In"....to the wall of of course....

Good luck to the new owners...

Pat

On another note, as to the expansion tank as a possible solution, that unfortunately will do nothing for the problem. Expansion tanks are only designed to help with closed loop systems on the cold side of the WH.

Originally Posted by Patrick Martinez

Hate to say it but it sounds like the plumber didn't install any strapping / brackets. Bummer, but likely the fix, if accessible is to block the piping at the closest area to pull it to a wall and hopefully secure it. Otherwise "I'm Going In"....to the wall of of course....

Good luck to the new owners...

Pat

I've bored a 1/4" hole in the wall near the shaking pipes before and pumped a can or two of that expanding foam stuff inside there. I know, I know, it's a definate bubba, but it's far less intrusive than putting a hole in the wall.

Originally Posted by Joshua Hardesty

I've bored a 1/4" hole in the wall near the shaking pipes before and pumped a can or two of that expanding foam stuff inside there.

Joshua,

Copper piping or CPVC?

CPVC has a LOT of compatibility issues with many products, even many common caulks (which are, of course, used to 'caulk around the pipes').

Good - Americas - FGG/BM/CZ™ System Compatible Program

Not good - FGG/BM/CZ™ System Compatible Program

Some good / some not good - FGG/BM/CZ™ System Compatible Program

Joshua, I think I'd put the whole in the drywall set some brackets / tube talons etc and be done with it. The drywall is an easy fix and can make it look like you were never there.

Jerry has a great point on the compatibility issues.

Copper. I actually see very, very few homes done in CPVC. Mostly condos and apartments.

As far as the allergy problem, try coating the inside of the nostrils with Polysporin each morning. It will help or may even eliminate you problems. It did for me. Have not had any problems in 2 years. I use to have horrible allergy problems in the spring and fall. I told my doctor about using it and he said if it works, do it.

Jon Randolph said


but you can just as easily make one. It is nothing but a piece of pipe capped on the end and installed vertically (with the capped end up) on the water pipes.


MMM no you cant! The IPC says.....


604.9 Water hammer.
The flow velocity of the water distribution system shall be controlled to reduce the possibility of water hammer. A water-hammer arrestor shall be installed where quick-closing valves are utilized. Water-hammer arrestors shall be installed in accordance with the manufacturer’s specifications. Water-hammer arrestors shall conform to ASSE 1010.( If you use the old method to make these 1/2 inch supply line use a 3/4 pipe at least 12 inches long it will not meet this standard. Over time will fill with water and become useless.)

WATER-HAMMER ARRESTOR. A device utilized to absorb the pressure surge (water hammer) that occurs when water flow is suddenly stopped in a water supply system.