Water hammer

[supton]

My new-to-me house has a wicked water hammer, but it's worst on just the bathroom vanity. Would putting a hammer arrestor on the washing machine help? I'm thinking it's too far away.

I have the water tank, then 15 or 20 feet to a tee. One side of the tee feeds the washer, dishwasher, kitchen sink, 15' or so of line. The other side of the tee feeds the problem vanity and is likewise 15' away. The washing machine, dishwasher etc do not seem to induce any hammer, but the one vanity on the other branch sure does.

I tried closing the valves on the vanity to reduce pressure, no change (that sink does have some wicked water flow!). I've added a bunch of hangers onto the copper pipes, but I don't see any pipe movement when we make the hammer occur.

The problem vanity is copper all the way to the faucet. Maybe changing the line from copper to a standard hose would fix? Give it something that can flex a bit, that is.

 

[Cujet]

Many homes have standpipes in the wall that are designed to trap air and eliminate water hammer. It's a simple solution that any plumber can make with just a "T" fitting and 2-3 feet of copper pipe with a cap at the top.

Over time, these can fill with water and the water hammer starts.

If your house has these primitive water hammer devices, you can evacuate all the water from your homes plumbing using a good shop vac. This will generally allow air into those pipes and solve the problem for a time. Or inject shop air while running water through the valve in question. Either will get air into the primitive hammer arrester.

Or simply install a modern water hammer arrester on or near the valve in question.

 

[Chris142]

So that's what those pipes in my wall are for! I never knew but I did wonder.

 

[A_Spruce]

Yes, the 12" stub of pipe above where the angle stops are located are there for water hammer. Yes, over time they can become water logged, the cure is to turn off the water to the house and open the highest and the lowest valves in the house to drain the system down, thus restoring air into the hammer arrestors.

Interesting thing, I just did a major bath remodel and the plumber deleted the water hammer arrestors, said they weren't needed anymore. I'm not sold on that notion, but it could be that municipal systems are better at regulating pressure to the house so that hammer isn't as big a problem anymore. I don't know, but, personally, I'd rather have them and not need them than to be without and have issues.

I think that there are arrestors that can be installed between the angle stop and the fixture. Skip the big box and go straight to a plumbing supplier, they would have it if it exists.

 

[Bailes1992]

I've never seen that done in the UK! Simple but bizarre fix.

It could be because we are better at maintaining/controlling water pressure over here, but generally we make sure all pipework is securely fixed and water hammer isn't an issue over here.

 

[Fawteen]

Originally Posted by supton
but it's worst on just the bathroom vanity. Would putting a hammer arrestor on the washing machine help? I'm thinking it's too far away.

The washing machine, dishwasher etc do not seem to induce any hammer, but the one vanity on the other branch sure does.


The simple way to stop the water shock is to close the vanity valves slower. There are a couple variables, but the real key is to slow the velocity of the water and not suddenly stop it, thus reducing the shock when a valve is suddenly closed.

You can always put an arrestor on the vanity under the sink.

Originally Posted by A_Spruce
Interesting thing, I just did a major bath remodel and the plumber deleted the water hammer arrestors, said they weren't needed anymore. I'm not sold on that notion, but it could be that municipal systems are better at regulating pressure to the house so that hammer isn't as big a problem anymore.


The "municipal system" has nothing to do with it. Anytime water is under pressure and there's a sudden change in velocity, shock can happen. In a correctly designed system in the house it's not an issue-most hand valves don't slam closed fast enough to induce noticeable shock. But some washing machines and dishwashers still have valves that slam closed and cause a shock. Newer piping systems are also more resistant to transmitting the sound of the shock, whereas copper and old galvanized can make a lot more noise if not designed well.

Originally Posted by Bailes1992
water hammer isn't an issue over here.


Then the UK has somehow managed to get around the physics of how liquids work inside a pipe. Is your water over there somehow compressible? Or did you manage to over come wave celerity inside a pipe?

 

[supton]

I've looked and don't see any standpipes, but the pipes for the showers and washer do have plumbing that I can't see inside of the wall (house is a ranch so vast majority of the plumbing is visible). I've seen the tees with the hammer arrestor but those are of course more work to install than one on the washer (see here). Although this morning I now see this which looks like it could be added under the vanity easily enough; I hadn't seen that before (just the ones with sharkbite tees and I have not worked up the courage yet to cut into water lines just yet!).

 

[bdcardinal]

To be honest, I have never heard of water hammer outside of commercials on ARCA races for Sioux Chief arrestors and now here.

 

[JTK]

It's odd that faucet taps induce the noise, where solenoid actuated valves on your appliances do not. It's typically the solenoid valves that do it because they snap full open and full closed so quickly. I'm thinking it's the specific plumbing run associated with the areas in question.