too much pressure?

18 years ago

Hi,

I just finished re-piping my entire house (except the hose bibs) with PEX to replace the 34-year old, ready-to-break-at-any-moment galvanized pipe. I installed a new Moen tub/shower valve in one bathroom (the other bathroom is just a shower, no tub) and now when I turn on the tub faucet, I get a fair trickle of water out of the shower head. I checked the spout, and it is clear. I even took the spout off and just let the pipe run wide open, and I still get water out of the shower head. I also know for certain that the shower valve is installed right-side-up (it has a stamp on it that says, "UP"! Kinda hard to get that wrong).

When the water is running at the tub spout, I get lots of good pressure -- MUCH better than I ever had with the old pipes.

The hot/cold lines running to the valve are 1/2" PEX. I also used 1/2" PEX to 1/2" drop ears for both the shower riser and the tub spout.

So, I am wondering...is it possible that I now have TOO MUCH pressure? Here are the changes I made to the overall system:

1) Replaced the main 3/4" gate valve with a 1" full-port ball valve. The output from that is reduced to 3/4" PEX.

2) Installed a whole house water filter (which should actually reduce the pressure a little bit, right?).

3) The line running to the water heater had been 1/2" galvanized. I replaced it with 3/4" PEX.

4) The old system was all branch and tee. The new system uses 3/4" PEX with 4 x 1/2" tee's at the kitchen (Sink, D/W, I/M), and then multi-port copper manifolds near the bathrooms with 3/4" inlets and 1/2" outlets.

Is my new plumbing system *too* good? :-) What should I do?

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Comments (9)

ctbosox
18 years ago
I wouldn't figure too much pressure, I'd look in the area of the tub/shower valve. Water is getting by the valve, or the diverter is partialy hung up, allowing water to go to the shower head.
dennisjones
Original Author
18 years ago
Well, it can't be the diverter because, like I said earlier, I tried without the tub spout installed at all (no diverter) and had the same problem. The valve is clear (as far as I know), it is installed correctly, and it is brand new, so I'm not sure what could be wrong with the valve.

Any other ideas? Still very confused.

- Dennis
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zl700
18 years ago
Yes it is possible to flow too much water through the T&S valve with the pipe and tub spout not being able to carry the capacity thus it backs up and exits the shower head (like partially closing the diverter on the spout)

Choices:

1. Bigger pipe, less bends to spout
2. Reduce water to valve.
3. Reduce pressure in whole house.

Did you get the Moen valve with built in stops? If so close down evenly a bit. Or use or install seperate valves
zl700
18 years ago
DUH,

Just reread your post

1/2 pex fittings can be very restictive, causing the pressure increase, backing up to head. (restriction at barbs)

Try replacing the drop from valve to spout with 1/2" copper and I'm sure your problem will be solved.
dennisjones
Original Author
18 years ago
No, the valve does not have built-in stops. But you've given me some ideas to work with. Thanks.

- Dennis
dennisjones
Original Author
18 years ago
No, the valve does not have built-in stops. But you've given me some ideas to work with. Thanks.

- Dennis
asolo
18 years ago
Just a quip....before I undertake any serious re-pipe job, I check the overall household pressure as a matter principal. I like to know what I'm working with. Pressure indicators are common, cheap, easily available and easy and quick to use.

Otherwise, tend to agree with zl700's thinking about it.
dennisjones
Original Author
18 years ago
Just to let you all know my progress...I replaced the PEX pipe and crimp style fittings with a piece of galvanized pipe (I'm not a plumber and don't have the expertise to do copper) and the problem is gone. Apparently, the *very* small opening (3/8"?) of the crimp style fittings was enough to restrict the flow to the point where water was forced up into the shower head.

If I had used the shark-bite style fittings instead of crimp style fittings, I might not have had the problem, but at this point the problem is solved and I don't care if I have a piece of galvanized going to the tub spout (I'm going to be moving and selling the house in a year or two anyway!).
zl700
18 years ago
Good to hear you corrected it!

The ID of those insert ftgs can be very resrictive. It is always better to attempt to sweep the pipe into an ell and use outside stiffeners if necessary to reduce kinking.

The fittings to your spout before replacing was like raising the diverter stem up halfway.

With exception to tub spouts, The restriction is hardly noticed on PEX piping systems, especially "home run" systems.