Noise in the shower/bath for hot water

[clockwatcher]

First time poster and practically first time at any kind of plumbing.

When using the shower/bath, putting the single handle valve to a comfortable temperature position (about 1/2 way) causes a very loud vibrating and kind of groaning sound directly in the wall area of the valve. Turning the temperature hotter continues the noise/vibration, but reducing it to colder makes it stop.

But, if you run the COLD in the vanity sink (full open), the shower temperature can be raised just hot enough to be comfortable without the vibration and noise.

I have taken the valve assembly apart, checked for debris or excessive wear and basically put it back together hoping to "fix" it, but it has not changed. I don't remember seeing anything visibly worn, but hey-I'm certainly not an expert so I'm open and very grateful for any insight into this problem!

[Glasshousebltr]

It's called water hammer. The way to fix is to install a T and a short length of capped pipe just before the mixing valve.

Bob

[clockwatcher]

Do I put the capped off T on the hot or the cold? What is a short lenght to you? Also, can I put the T in the basement? (the bathroom is on the first floor so about 5 ft before the mixing valve)

Sorry for all of the questions, I am really thankfull for the advice, I would have no idea this could fix the problem I am having.

[clockwatcher]

Update-

I put a gate valve on the cold supply thinking that the cold pressure was too high. This did not fix the problem.

So I turned off the cold and took the mixer valve apart again and found that the hot is barely flowing. I think the hot supply is clogged, but I don't have access to where it connects. I'm thinking about sticking something down in there to try and open it up...can I do serious damage to the mixing valve this way? If I disconnected the hot supply at a point in the basement and tried running cold back down through the supply, will the mixer valve allow this and would it even help? It is a "Kingston" brand mixer valve.

Thanks for any advice, I would love to get this hot supply opened up a bit without tearing into my shower wall!

[LazyPup]

It is not water hammer..water hammer only occurs when a valve is turned off and it produces one or sometimes two loud banging sounds like someone rapping on the pipe with a hammer.

A water hammer arrestor will not resolve the problem.

A continuous vibrating or groaning sound is a result of rapidly fluctuating pressure. This type of noise is generally isolated to the function of one faucett or valve. Formerly we saw this problem often as a result of a loose faucett washer that was vibrating and causing rapid pressure changes. The solution there is to replace the Bibb Washer in the faucett.

We also see the problem in spring activated pressure balancing valves such as found in anti-scald shower mixers or pressure reducing valves (PRV's) which are sometimes in stalled on the water main.

In the case of your shower mixer it is a result of a pressure imbalance between the Hot & Cold supply pressure to the valve. In this case the Hot water pressure is lower than the Cold water pressure.

Understanding that all pressure in your water distribution system is generated from the supply source, whether that is a home well pump or a municipal supply, it would stand that the pressure is equal up to the point where the Hot & Cold water systems divide at the water heater.

We must then consider what conditions could cause a pressure drop on the Hot water side of the distribution system.

1.The cold water supply valve to the water heater MUST BE a full bore type valve, either a gate valve or ball valve, not a globe valve, and that valve must be kept in the full open position.

2. If flex lines were used to install the water heater they must be equal to or greater than the diameter of the pipe. Even a slight downsize in the lines will cause an increase in velocity and a proportional decrease in pressure.

3. If the water heater is fitted with "Het Trap" type dielectric nipples it is quite feasible that the heat trap may be slightly calcified, which reduces effective working diameter and here again, a decrease in diameter causes an increase in velocity and decrease in pressure. (Solution-replace the dielectric nipples)

4.If you have hard water and if this is an older water heater which has not been periodically flushed out it is possible that minerals have built up in the bottom of the tank and are restricting the flow of water from the dip tube. This would also result in increased velocity and decreased pressure.

5. Question here. Are all the water lines downstream from the water heat location the original lines installed during construction or were the perhaps changed during a rehab? If they were changed were they replaced with the exact same size of line or did someone perhaps increase a line size in the false assumption that it would provide more pressure? By example, typically a small to medium sized residential structure will have a 3/4" supply line and that 3/4" line should run to the point where the water heater Tee's off. From that tee both the Hot and Cold water lines must be 1/2" to insure even pressure distribution. If either or both lines were increased to 3/4" then either line is now capable of carrying the full volume of flow from the source and results in irratic pressure on both the hot and cold distribution lines.

6. Is this an older home with Galvanized iron pipes? If so, it is probable that the pipes have calcified on the inner walls which is a common problem with older galvanized pipe. The mineral buildup inside the pipe reduces the effective diameter of the pipe which again results in increased velocity and decreased pressure. Typically the problem of mineral buildup is much greater on the hot water pipes. Solution-replace the defective pipe.

7. Are there any zone valves on the distribution piping? If so, check the valves to make sure they are fully open.

So far this has addressed the permanent solution however in your post you stated that you have been able to temporarily alleviate the problem by turning the lavatory cold water faucett on, which in essence deminished the working pressure on the cold water line and once the pressure on both hot and cold reach equilibrium the noise and vibration stops.

As a temporary solution you could install a throttling type valve (globe valve) on the cold water supply line then reduce the cold pressure by partially closing that valve. This will result in a slight decrease in working pressure but it will not decrease the volume of flow. The slight decrease in pressure will not effect the overall performance of your shower.

[clockwatcher]

Thank you very much for explaining the concepts to me and all of the ideas, I think I've got it narrowed down to reduced diameter (maybe debris) of the section of hot water pipe coming up to the mixer valve.

I've come to this conclusion due to:

All water lines past the water heater are 1/2" galvanized.

Hot water pressure every where else is great including the vanity sink which is on the same line, and after the shower (the shower hot supply is a T off of this same line).

I did use a globe type valve on the cold and have fiddled without much success, but the good news is I can isolate the hot now.

All of the water pipes are galvanized - the hot side pressure coming out of the of the mixer valve is very low which makes me think it is obstructed.

Replacing the obstructed section (possibly 4 feet) will require access through the tiled bath area. Honestly, I am hoping to come up with a temporary fix until next spring when I will have some more $$$ to redo more in the bath although I have a bad feeling running the sink is not going to be enough for 3 of us to take nice hot showers all winter.

Tonight I plan on borrowing a coworker's air compressor and blowing out that section of the line. If that doesn't work, what horrible things will happen if I cap the bottom of the section and fill it with CLR for 1/2 an hour or so? I'm guessing to a Master Journeyman, that probably falls in line with heresy. Sorry if I'm offending!

Anyway, if there is anyway to open up the diameter of the pipe without any demo (until I can replace it all with copper next spring), I'll take it!

[LazyPup]

Absolutely do not put CLR in the lines. On the one hand it is very unlikely that CLR or any other chemical would have enough effect to produce a substantial result while on the other hand we must always remember that these lines are your "potable water supply" and introducing any chemicals into the lines could potentially prove to be deadly for you or your family. In fact, it is against the law to intentional put any chemicals other than bonefide water treatment chemicals in a water line.

When confronted with a problem such as this it is apparent that ripping out a shower enclosure or a tile wall can be a very expensive undertaking but often we overlook the obious. You may be able to easily access the pipe by coming through the wall from the opposite side. Once your into the stud bay it is basically the same task from either side.

[clockwatcher]

Ok, yes now I feel like an absolute moron for thinking of doing that!

My problem is that there is a chimney on the other side of the wall.

Trying the air compressor now...


Whelp, looks like I'm going to have to do some damage.

Think I'll probably call a real plumber now.

[clockwatcher]

Well, $80 (minimum 1 hour) later I have a shower that works better than ever. The professional I called took everything apart, had me turn the water on and off a couple of times, put it all back together and wala.

Makes me wish I would've called sooner.

I did learn a bit about plumbing though. In the end it was an anti-scalding valve built into the faucet that was clogged.

GG