leaking water valve behind vanity

[Tethyss579]

Hi - I am doing a bathroom renovation. After removing the vanity I noticed mold/moisture in the bottom of the drywall. I removed the drywall and upon closer inspection it appears the water valves were modified and pinched off/welded in some way.

It appears my renovation may have started a slow leak from the hot water side that was cut off and pinched welded? Both water pipes were modified this way and the top of the copper pipe on the left is moist. The pipes go down into the concrete so I'm not sure if there is any leaking there but once I repair this I will wait and inspect again.

I have a few ideas on how to cut this out and replace it (I am fine sweating copper) but wanted to get some feedback. How would you recommend I repair this? Thank you.

 

[Jeff Handy]

You can just cut off the pinched tops.

You should probably sweat on some copper threaded adapters, then screw in some water hammer arrestors on top.

Maybe the water hammer arrestors come in compression style, so you don’t even have to solder right up close to that blocking and drywall.

Also, the clamps that hold the old air chamber risers are too tight.
You can change them out with new clamps that hold firmly, but allow the risers to slip up and down slightly with temperature changes.

 

[Tethyss579]

Why couldn't I just cut them off below the tee and install a new elbow to come straight out to a new valve? Why would I need water hammer arrestors? I do not recall any issues with water hammering in the original sink/vanity.

 

[Jeff Handy]

Those risers are designed to hold some air, to act as a shock absorber to stop water hammer noise.
Sometimes, the trapped air will be absorbed, and the air chambers stop doing their job.

You don’t really need them at a vanity as much as you do at a fixture with a fast closing valve, like a washing machine or dishwasher.
The moving water stops very suddenly, and so the pipes can shake and make noise, unless you have air chambers, or water hammer arrestor cylinders.

But even a modern vanity faucet can go from full stream to full shutoff very quickly, so either leave the air chambers there, and solder on some caps, or even better to solder on some copper female adapters then thread in some water hammer cylinders.

Also, sometimes a fixture elsewhere in the house can cause water hammer at other fixtures on the same branch, so leaving some form of water hammer protection is a good idea.

You can also get water hammer arrestor cylinders in compression or sharkbite style.

 

[Rickyman]

Why couldn't I just cut them off below the tee and install a new elbow to come straight out to a new valve? Why would I need water hammer arrestors? I do not recall any issues with water hammering in the original sink/vanity.

That’s how I would do it. I don’t see hammer arrestors here that much.

 

[Jeff Handy]

To each his own.

However, the hot line has another branch teeing off going somewhere else.

The cold line has two other lines going somewhere else.

If those other fixtures have water hammer now or in the future, you can get it making water hammer at these connections also.

Putting on arrestors, or keeping your existing chambers, is cheap insurance.

 

[TomFOhio]

You could cut above the tee's and either sweat on caps or use shark bite caps if its close and your afraid of burning something.

 

[Diehard]

Agree!
No reason to remove tees and replace with elbows.
Just cut and cap above tees.