View Full Version : Shower Drip Mystery

07-18-2007, 11:59 AM
Well, it's a mystery to us - maybe not to a plumber <g>.

We have a stall shower with a hand held shower head - in the master bedroom.

Overnight, and if the water hasn't been used in the house until say, 8 or 9 a.m., the shower head will start dripping. After the water has been used, it will stop.

When my husband gets up at 6 a.m. for work and uses the water, it won't start dripping again until around 11 a.m. - when I sleep in late. Yeah, don't tell me to just get up earlier :)

If I get up around 9 a.m. and use the toilet in the main bathroom, I will hear a swish sound like the water pressure is high.

We have a water pressure reducer although it hasn't been replaced since we have lived here - over 20 years. Our water pressure has been checked by a plumber in the past and it hasn't been over. We also have a pressure reducer tank (I guess that is the name) on the line right before our gas water heater. We had to have that put in when water company changed lines and the pressure increased so much that it made our tank leak - well, that is what we think.

My question - is our one handle Moen shower faucet just worn out (unfortunately, that was put in by Bath Fitters and we failed to get the model of the faucet so I can't order a free cartridge replacement - which I would do since I have done that with other faucets in the house. The faucet is 5 years old and the models change so often that I can't figure out which one ours is and Bath Fitters told us the incorrect model because it does not match the model picture on Moen's website.

OR is it a water pressure problem? We don't want to replace the faucet (which we don't know how to do and would have to pay to have done - after purchasing it through a place like Home Depot) just to have the problem be too much water pressure making that one leak as well.

Seems strange that the faucet doesn't leak all day while I am here using the water. Maybe it is just the faucet cartridge failing therefore it won't keep the faucet from dripping if the water pressure is the least bit up like it would be when no one is using the water.

Thanks for advice!


07-18-2007, 12:18 PM
With the pressure reduction valve, you also need an expansion tank. If you have one, and it is 20-years old, it is probably shot. Sounds like the classic water expansion problems when the WH heats the water after a shower or any other use, it expands and temporarily raises the pressure. Your old valve is leaking a little until the amount that expanded is leaked out, returning the pressure to something the valve can handle.

An expansion tank has a rubber bag or bladder in it with one side pressurized and water in the other. When the water expands from heating, it compresses the air. When the bladder is shot, it fills up with water and there is no place for the heated water to go but to increase the pressure. Since water doesn't compress, it expands rubber hoses, leaks out, etc.

Gary Swart
07-18-2007, 02:49 PM
What you referred to as, "a pressure reducer tank" is the expansion tank. It is shot and the expanded water is finds less resistance in the shower faucet than the T/P valve on the water heater. Expansion tanks are screwed into a fitting that is installed in the incoming water line. Since you already have an expansion tank, replace it is simple. You need to know where your pressure reducing valve is set. The expansion tank is air-charged to the same pressure just like putting air into a car tire. You must exercise caution doing this so as not to put too much pressure in the tank and blow the bladder up. Watts discourages using an air compressor for that reason, but if you are careful, that will work. You can use a bicycle tire pump. It doesn't require much volume of air. If you don't already have a water pressure gauge, they are readily available at any hardware store for under $15. Attach it to any faucet in your home that will accept a garden hose. Now turn the water off, relieve the pressure by opening a faucet, unscrew the old expansion tank, screw the new one on, and turn the water back on.

07-18-2007, 03:45 PM
It may also be that your pressure reducing valve may be shot...
The key is that while you are using water, there is no leak...
When you don't use it, there is a leak - If the PRV is leaking by slowly, it will take a while to allow enough water in to over-presurize the system...
To test if it is an expansion take issue or a PRV issue, use water like normal then, when the water starts dripping, use some COLD only until it stops dripping (via a sink or toilet etc...) - do not use hot...
If the leaking resumes, it is most likely the PRV...
If the leaking does NOT resume, then it is probably the expansion tank...

07-19-2007, 10:42 AM
Thanks for the replies.

I didn't make myself clear in the first message - the expansion tank is only about 4 years old - it wouldn't be shot by now, would it?

Also, answering markts30 reply, when the shower faucet is dripping and I use the toilet in the other bathroom plus use the cold water only in the bathroom faucet, the dripping STOPS.

So...you are saying that the expansion tank is the problem - even though it is only 4 years old...yikes.

That brings up another question - how does a person know when the expansion tank is working? Seems like it used to make a "bang" noise now and then but I haven't heard that in a while.

And...no one thinks it could be the cartridge in the Moen faucet? It is 5 years old. We have had drips in our other faucets - kitchen, and both baths - I have replaced the cartridges (free from calling the companies) and the leaks have stopped.

Thanks for further info.


07-19-2007, 12:09 PM
When set up properly, the expansion tank is mostly air. If you tap on it and it sounds more like a bell than a thud, it is still probably okay. If it feels heavy like it is full, it probably is. Also, it has an air valve (schrader valve) on it under a cap just like those on your car tire. If you check the pressure and it leaks water, it is shot.

If the tank wasn't presurized for your house (i.e., too low), it would expand and contract much more than it was designed for and could die within that timeframe as well. Or, it could have just been a lousy one! It needs to be big enough for the house as well. This is determined by the size of the WH, and the temp of the incoming water and how hot you set it to. The bigger temperature rise and the more water, the bigger the tank needs to be. If it is too small, again, it will strain the bladder and it will rupture sooner.

07-19-2007, 07:13 PM
....Overnight, and if the water hasn't been used in the house until say, 8 or 9 a.m., the shower head will start dripping. ...just a bit of water? dripping out after you left the diverter pulled to send water to the shower? Could be nothing serious. After each shower use, press the divertor back down to let the pipe drain itself out instead of leaving it full of water.

BTW, your sentence quoted isn't clear to me.


07-19-2007, 09:29 PM
just a bit of water? dripping out after you left the diverter pulled to send water to the shower? Could be nothing serious. After each shower use, press the divertor back down to let the pipe drain itself out instead of leaving it full of water.

BTW, your sentence quoted isn't clear to me.



This is a shower stall so there is not a bottom faucet. I am talking about a hand-held shower head.

To make my sentence more clear, well, the shower head does not drip during the day when water is being used - it only starts dripping in the morning about 4 hours after my husband has left for work and before I get up in the morning and use the water. On my husband's days off, he gets up later and the shower will start dripping since he has not gotten up at 6 a.m. It is can be a fairly fast drip or a slower one.

The reason I was thinking it is the Moen faucet cartridge is because our bathroom sink faucets have dripped over the years and I have called Moen for replacement cartridges and that fixes the problem. But, like I said, unfortunately, I don't have the model number for this single handle shower faucet plus my brother said it is more difficult to replace the cartridge in these types so I don't know if I could do it myself. I am the "plumber" in the house, husband knows less than I do :)