low pressure from new valve/diverter

Hello all,

I have installed this Moen valve for an overhead rain shower: MOEN Rough-In POSI-TEMP VALVE W/STOPS 62370

w/ this diverter for a handheld: Moen 3372 Three Function Valve, 1/2" CC Connection

Sorry, couldn't get links to work.

I sweated ~ 3 inch copper to each port to which I connected PEX to the original copper supply via SharkBites. I then ran PEX to a drop ear elbow for my overhead and then more PEX to another drop ear for my handheld. I wanted to check everything out to make sure I had no leaks before I close the wall in. I did this without the showerheads installed, I just collected the water in the bucket from each drop ear. The good news is there were no leaks but the bad news is it seems like the pressure is really low, even when only one port was on at a time. I don't know whether this is due to the fact that the water now has to travel further, or if the water has just not been supplied to the bathroom for such a long time I did not wait long enough for any pressure to build. Is this possible? Also, I do not have any shut-offs in my supply that could be partially blocking any water. The pressure beforehand was pretty decent. Any help would be great!

Thanks,
Lucas

Did your valve rough-in come with a pressure test blank? It is best to flush the lines with the blank in place lest crud gets into the delicate pressure balance valve. If the valve gets crud on one side, the balance mechanism may reduce the other side to match.

LLigetfa said:

Did your valve rough-in come with a pressure test blank? It is best to flush the lines with the blank in place lest crud gets into the delicate pressure balance valve. If the valve gets crud on one side, the balance mechanism may reduce the other side to match.

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I'm not sure. My wife picked up the valve from Ferguson's; only came with billing receipt and a plastic bag, no instructions or anything. What would the blank look like?

The blank would fit where the valve cartridge does but unlike the cartridge, has no inner workings.

LLigetfa said:

The blank would fit where the valve cartridge does but unlike the cartridge, has no inner workings.

Click to expand...

Then no, it did not come with a blank. Should I take the cartridge out and inspect inside of valve?

A wise person here made the following suggestion and I lay no claim to it, being merely a parrot.

Fill a white sink with water and then rinse the valve in it. The white sink should show up any dirt that may have got caught up in the valve.

LLigetfa said:

A wise person here made the following suggestion...

Click to expand...

Ah, found it. It was Phil Lloyd.

https://terrylove.com/forums/showth...e-balance-valve-be-reducing-my-water-pressure

Can anybody confirm that the problem IS NOT the fact that the water has to travel a couple more feet to reach the heads, or NOT the fact that I did not leave the water on long enough to allow pressure to build?

Thanks.

If water traveling a couple of feet could have that drastic an effect, an upstairs shower tens of feet away would not be possible. I'm thinking to factor maybe 2 or 3 PSI per hundred feet of horizontal run depending on the flow rate. Vertically, it is around 1 PSI per 2 1/2 feet.

LLigetfa said:

If water traveling a couple of feet could have that drastic an effect, an upstairs shower tens of feet away would not be possible. I'm thinking to factor maybe 2 or 3 PSI per hundred feet of horizontal run depending on the flow rate. Vertically, it is around 1 PSI per 2 1/2 feet.

Click to expand...

This is what I was thinking, and why the problem must lie in the valve. Thanks.

Pex has a smaller ID than the same diameter (OD) copper. So, if the other bathroom has all copper, it could have more volume available than with pex. Pressure doesn't 'build' in a system...it is the same everywhere with the exception of elevation - it goes down slightly with increases in elevation. For practical purposes in a typical house, it isn't noticable. What you may be experiencing is a difference if flow capacity, not pressure - two different things. A fire hose at 20psi will flow a lot more water than a straw at 100psi.

Current shower valves may have internal restrictions in them, since the shower heads can only be 2.5gpm max per code. The outlet to the tub is unrestricted, but that capacity is determined by the supply lines and the valve size.

A sharkbite relies on the internal ferrule to stabilize the pex so the o-ring and teeth can bear against a stiff surface. This may be smaller than a pex fitting, but still further restricts the ID and therefore volume.

All,

I turned off water supply, drained as much as possible from heads and then removed cartridge from valve and took a look. What remaining water was in supply lines seemed to be dribbling out at an even rate for both hot and cold. Regardless, I removed the valve and disassembled what parts I could and soaked in a white sink. Everything seems to be clean and in working order, so I removed diverter valve, and much to my own ignorance, realized it is a push/pull type, where pulling opens the line and twisting controls the diversion. When everything was installed this must have only been pulled out partially, causing the weak flow. I will put everything back together tomorrow and hopefully will get some decent pressure. Thanks for the help.