leaky shower (odd)

House is ~14 yrs old and a few yrs ago the downstairs shower, which isn't normally used, developed an odd leak. If you turn on the water to the bath spigot, no issues, no leaks. Turn on the shower, water comes out the shower head, but there is a leak-behind the wall- runs out on the floor. I removed the cover plate around the mixer valve with the shower on and didn't see a leak there at the valve. So, I assume there's a leak either in between the valve and shower head or at the spigot. I was wondering what the pros thought.

I will say that the construction of the house is "average", as in not very good, and the plumbing work appears to be fair to poor.

Thanks for any help!

edit: the valve is a Delta

Plumbing: Shower

Since you are only experiencing the leak when you run the shower head there is only two possibilities.

1.) The leak is in between the valve and the shower arm. It could be at the connection to the valve, the pipe, the connection of the pipe to the shower ell, or on the threads of the shower arm.

2.) When you divert the water to the shower arm you are placing a constant pressure on the tub spout that usually doesn't exist. Since usually the water flows through, but when diverted you are now potentially seeing a slight leak from the pipe leading to the tub spout you are usually overlooking due to lack of pressure on the leak.

leak

Try to unscrew the shower arm out of the wall. It will probably break off in your hand because it is already cracked and about to fall off. Then you will have the project of removing the piece left in the elbow.

Forgot to mention that I removed the shower arm cover and looked for a leak there and nothing. Then I removed the arm and plugged the outlet and still a leak. Bummer. Oh well, I guess everything can't be easy.

Maybe it's coming from the tub spout area. I can't see it leaking when looking in the area at the mixing valve so maybe the leak is below it. I guess I'll try and remove the tub spout and see it I can see anythign wrong there.

If that doesn't turn up anything, since I can't see the leak I guess I'll have to open the wall behind it- I was already planning on having to do this.


Thanks!

If the diverter valve is in the spout the spout is a good possibility.

leak

In that case the most likely, and possibly only, spots for the leak are at the shower arm elbow or where the riser attaches to the valve. The drop to the tub spout could be leaking but it would normally also leak when filling the tub.

The diverter valve for the shower is in the tub spout.

ok, I did some more checking on this. I used one of those small mechanic mirrors and a flashlight and went in thru the open area around the mixer valve and looked around some behind the wall with the water pressure on the plugged shower head- not easy to see back there.

The leak is where the tub spout connects to the piping behind the wall- really strange, dunno what is going on there but that's where it is. THe tub spout is very tight. I am pretty sure I'm going to have to hack into the wall, but figured I'd try and remove the spout first to see if I could gain any insight into what's going on. I tried loosening it by hand and it wouldn't budge. How do you usually remove these? Rag and pipe wrench? I realize I might damage it, no biggie if so. It appears the spout is cast onto a galvanized section of pipe. Again, this is delta stuff.

Tub spouts are usually thread on or, slip on. Depending on the spout many times i crush and break off the outer shell so I can get a wrench on the pipe stub and grip the spout with channel locks to unthread it. Slip on spouts have a locking screw in a hole underneath...

If it is a screw on, try using something that will fit into the spout's down turned end. That should give you a fair amount of leverage. If you are going to replace it, a pipe wrench on the outside probably would work, but would likely destroy it. Galvanized piping is not a great thing in fresh water piping. If the el in the wall is also iron, you may be in for some work - the threads could be shot. What is the rest of the piping in the house? If you have any access back there, you may want to spray some PBlaster on it - it's one of the better penetrating oils available and may help.

You'll want to replace the galvanized iron nipple with a brass one if the threads and fitting are still okay...it should last a very long time.

Thanks for the replies.

the spout is not a slip on- there is no set screw underneath. I'll get out the wrenches.

The house has copper tubing and a few sections of PVC in another bath that I discovered hidden when doing something else (guess they ran out of cu in the afternoon! )

ok, the spout came off no problem and I found the leak. Out of the bottom of the mixer valve there is a ~6" section of galv pipe, then an elbow, and another ~6" section of galv pipe that the tub spout screws onto. The elbow has a pinhole on the "back" of it- about midway on the long radius, which is why this was so hard to see. I guess it was a poorly cast part and eventually rusted thru.

I have NO idea why they used galvanized pipe here as it is copper into the valve and then copper out to the shower head.

So, when I remove the pipe, I take it that it's best to replace it with a similar layout but with brass pipe?

Also, the mixer valve is "loose" as in not mounted on a stud. I assume this isn't the right way to do it but not sure if I can do anything about this

Copper with galvy¿ Can you say electrolysis¿ Odd that the galvy was the one pitted if this is the case, though.

ah nevermind still half asleep!

Steve can you open up the wall on the backside behind the tub for access?
Usuall the tub backs up to a closet or something where you can cut the sheetrock and get access.

Yes replace the nipples and elbows with brass. On the nipple going out to the tub the length may change if the spouts are different. If you make it up out of 2 nipples and a coupling the added thread joints give you a fudge factor which may come in handy,

As for securing it do what you have to do.... You're there and can see what it will take to secure it.

unfortunately I have to move the waterheater to gain access to the wall behind it so I can cut in for repairs. Oh well. This is why I am also debating changing the ~14 yr old WH (my other thread)

They put wooden wedges between the shower wall and the horizontal copper tubes to the mixer valve- this was their method of securing it .

Thanks to everyone for the help