New Moen Shower Cartridge - Trickle of water

[k-n]

New cabin, new plumbing. It's all pex 3/4 inch until it reaches a T to the fixtures. I have very good water pressure and have tested the water flow before/after shower cartridge. I am currently only allowing water pressure on the cold side and the hot side is still blocked until the floor goes in under the HW heater.

This is a moen "entry level" shower/tub cartridge. I have both hot and cold plumbed but have only pressure tested the cold side. Turning on the shower valve gives me a very slow stream of water just enough to pour and not drip but by no means measure in gpm. More like GPH...

This cartridge does not have any screws or adjustments to balance flow. Instead, it uses a plastic gear-like thing to stop the handle from going too far into the hot side.

It is not upside-down though it doesn't matter. I've spun it all the way around looking for the spot where it will flow. I don't think there are any pieces of plastic or other junk in the pipes but I guess it's possible. I can pull out the insert and check, I guess.

Any other suggestions that I'm overlooking? I've not seen a cartridge that required hot water side pressure to work on the cold side but I'm not a plumber, either.

 

[LLigetfa]

I am currently only allowing water pressure on the cold side and the hot side is still blocked

That is your problem. The pressure balance spool is throttling the cold side to match the hot side pressure.

 

[Sponsor]

 

[Terry]

That is your problem. The pressure balance spool is throttling the cold side to match the hot side pressure.

Yes, pressure needs to be equal on both sides of the valve for it to work. This is standard for the Posi-Temp pressure balanced valve and the other brands that pressure balance.