Slow Drip on new valve install - how to resolve?

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BrittanyATX

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Hi y'all. This is my first post, so hopefully I'm posting in the correct forum.

I had a plumber install a new tub/shower valve in my guest bathroom (Union Brass 531C valve). It is the old style with an individual valve for each the hot and cold side and then a separate center diverter for the shower. After the plumber installed, I noticed that the water would slowly drip from the tub spigot for about an hour after water was turned on and then turned off from either the hot or cold side. Water would also drip from the tub spigot at a slow rate when the water was on shower mode. The plumber said this was typical for new installs and that it would stop after a few weeks. Well, it didn't and after many call backs the plumber said one of the valve stems must be bad and that I needed to get with the manufacturer.

Union Brass was very helpful and sent me new valve stems and diverter. Unfortunately, the plumber refused to answer, so I got on the phone with union brass and they walked me through how to replace the hot/cold valves and diverter. But, after installing all replacement parts I still had the same problem. I spent 3 hours on the phone with them and ultimately they don't know what is causing the dripping. The previous valve that was in the wall didn't drip. The new one was tied into the old copper pipes via soldering. Even when I cut the water off to the entire house for the day I was working on this, the water would drip out of the tub spigot for the same slow hour long drip rate and then stop dripping eventually.

Any ideas on what is causing this and how to resolve it?
 

Jadnashua

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First off, what the plumber did could get him in trouble...you can repair an existing, non-compliant install, but you can't legally replace it without the valve having anti-scald technology. While possible to implement that with a 3-handle valve assembly, yours is probably not done that way.

Second, try this: when finished with your shower, leave the diverter part way between tub and shower for awhile. This will let the water trapped in the riser to the shower head drain out. What might be happening is when you quickly turn the diverter back to tub position, the water in the riser is trapped, but the seal isn't perfect...it can take a long time for all of that water to drip out the spout. If that doesn't resolve it, there's some other problem. This doesn't typically happen with a tub spout diverter, since the water in the riser can freely drain out when it goes back to the tub. There can be some in the shower arm itself, but that would drip out the shower head verses the spout, and that can take some time as well.
 

BrittanyATX

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Yes, both the plumber and I knew the install I was requesting does not meet modern code. I told him I wanted to replace the existing 3 valve system with a new 3 valve system to maintain the historic look, and that I knew modern code required a single mixer with an anti scald valve. I asked if he would agree to install this anyway.

During troubleshooting with the manufacturer, I had the diverter to the shower open the entire time, and also would periodically bring the shower head down into the tub for additional draining. The shower head does not leak at all. This slow tub spigot drip also exists regardless of if the shower is run or only the tub is run. Any additional ideas on the root cause?
 

Jadnashua

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There are ways to make your valve anti-scald, but it gets more complicated. They do sell 'stand-alone' anti-scald valves that could be plumbed in while retaining a 3-handle look. The plumber must not treasure his license...

IF it's not the shower riser full of water leaking back out the spout, then it must be one of the supply valves leaking...if you've replaced the stems and that didn't fix it, IF it has replaceable seats, that would be the next step. IF it does not have replaceable seats, the valve body is defective. They do make tools to resurface the seat, but I have no experience with them and do not know how well they would work. Your valves may not use a conventional valve seat, and may be a cartridge. While not common, you may have received defective ones. The odds are against having two defective sets, though.

While you're investigating, it wouldn't hurt to double-check your water pressure. Code calls for no more than 80psi in a home. If yours is excessive, the valves may be having problems keeping their seal. This is easy to check with an inexpensive pressure gauge. The easiest is probably one designed to screw onto a hose bib, either outside, or say to your washing machine. It should also fit on the drain of the water heater, but then, could become too hot to easily remove. If it exceeds 80psi, then you should install a PRV and an expansion tank to regulate it to something more reasonable.
 

Terry

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Most tub and showers will slowly drip for 35 minutes after using the shower head. There isn't anything I can do about that.
So yes, it takes a while for water to slowly drain from the pipes going up to the shower head. I see this all the time on every home I have ever worked on.
Next!!
 

BrittanyATX

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Most tub and showers will slowly drip for 35 minutes after using the shower head. There isn't anything I can do about that.
So yes, it takes a while for water to slowly drain from the pipes going up to the shower head. I see this all the time on every home I have ever worked on.
Next!!

Hi Terry,

The drip is not from the shower head, it is at the tub spigot. The drip occurs if either the hot or cold valve is turned on on the tub, even if the shower portion is not turned on at all and only a bath is run. Is this normal? The drip rate is about one drip per 9 seconds for the first 30 mins and then slows down until it stops after the hour.
 
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