Shower leaks only w/ hot water

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Old 10-06-15, 06:29 AM
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Shower leaks only w/ hot water

I have a tub with shower head on the first floor which leaks into the basement. I can access the underside of the plumbing and the leak is dripping from inlet water line somewhere above, not the drain. It only leaks with the shower on with hot water (no leaks with cold water showers or with hot/cold baths). I believe it's a Delta faucet.

Would a bad control valve in the faucet (single rotatable knob) cause this unique problem?
 
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Old 10-06-15, 06:39 AM
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I have had problems like that in the past but it has always been with faucets having separate hot, cold and shower divert knobs. But... anything is possible. What is on the back side of the faucet? Is that wall into a closet?

First I would remove the knob and escutcheon on the tub side of the faucet to see if you can spot the leak from that side. If not you'll need to cut a hole in the wall on the back side to have access to the faucet body and piping to locate the source of the leak. If it's a closet that's best because you can just screw up a piece of paneling to cover the hole and be an access panel for the future. If the back side is visible there will be some sheetrock repair and painting in your future.
 
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Old 10-06-15, 07:44 AM
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Thanks for your input - I agree with looking at the faucet first. Plan to do that tonight.

I'm just confused on how the leak could be isolated to the hot water shower only... I would think a bad control valve would leak with both a hot shower and a hot bath, or a hole in the shower head feed would leak with hot or cold showers.

The backside of the faucet is a wall for the toilet alcove/area with tile 3 ft up the wall. Hopefully I don't have to open the wall, but if I do, it'll be a nice reason to get rid of the dated wall tile.
 
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Old 10-06-15, 09:53 AM
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The leak may be a crack in the shower riser that opens up only when it expands from the temperature of the water. Keep this in mind when repeating the leak test at the time you are making the repair.

Alternatively your shower faucet may be of a type where, as the control is advanced from cold through hot, the overall volume increases. At a certain point near the hot part of the range, the pressure is high enough to squeeze through a leak in the shower riser pipe.

Hint: If you unscrew the shower head, allowing a higher volume and in turn lower pressures, does the leak stop even with full hot setting?

For tub baths, the pressure in the lines for mixed hot and cold water is somewhat less even if the diverter does not fully close off the shower riser when letting water out of the tub spout.
 

Last edited by AllanJ; 10-06-15 at 10:18 AM.
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Old 10-06-15, 01:15 PM
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AllanJ -- thanks for your information. Your answers definitely give answers to what I was confused about. I'm going to take off the escutcheon and knob tonight and see if I can visually see the leak. If not, I'll try your suggestion with removing the shower head. In either case, if it's not at the control valve, it appears I'll be opening the wall in the near future.
 
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