What's the bottom line on flow restriction for shower/bath tub

In California and maybe all of U.S, is there a specific law regarding flow restriction on shower systems.
In the case of shower only, does the flow restriction happen at the valve or at shower head or both. Is this dictated by law or by how each mfg happens to design it.

in my case, even with shower head off, water is low flow. I replaced a brand new cartridge and still low flow. when cartridge is removed, flow is huge. It's a Price Pfister 08 with pressure balanced cartridge. I'm starting to think the pressure balancer is the cause of so much reduced flow. Wonder if a thermostatic valve will have higher flow.

in the case of shower and tub, shouldn't the tub be unrestricted?

Thanks

The tub is unrestricted. Shower HEADS are limited by law to 2.5 GPM, and some manufacturers put a restrictor in the outlet to the shower head, but that is not mandated.

jimbo said:

The tub is unrestricted. Shower HEADS are limited by law to 2.5 GPM, and some manufacturers put a restrictor in the outlet to the shower head, but that is not mandated.

Click to expand...

Would you be able to suggest any models that are not restricted before the shower head? The Price pfister 08 valve is not unrestricted to tub. Takes for ever to fill tub. Kinda useless.

The flow rate is determined by a few things: pressure, restrictions, and diameter of the supply pipe. NOrmally, the pressure balance spool does nothing to reduce the flow until one side's pressure drops.

Each valve will have a flow rate for a specific inlet pressure shown on its spec sheet. Raise the pressue, more flow, lower the pressure less flow. If your supply pipes are old and there's some galvanized piping in the system, you could have good static (no flow) pressure, but the inside is like a soda straw.

jadnashua said:

The flow rate is determined by a few things: pressure, restrictions, and diameter of the supply pipe. NOrmally, the pressure balance spool does nothing to reduce the flow until one side's pressure drops.

Each valve will have a flow rate for a specific inlet pressure shown on its spec sheet. Raise the pressue, more flow, lower the pressure less flow. If your supply pipes are old and there's some galvanized piping in the system, you could have good static (no flow) pressure, but the inside is like a soda straw.

Click to expand...

I attached a gauge to where the shower normally goes and got 65lbs. I took the cartridge out and turned on the water supply and it was a massive stream of water that came out. So I have no doubt that it's the PP 08 valve cartridge with balancer that is severly restricting the flow. I'll keep looking for something like the Grohtherm.

The valve body to the shower riser is the restriction, which is why I install my shower valves inverted when the valve's design allows it. (Moen is one of the few it cannot be done) Otherwise, I pipe the bottom, (tub), outlet up to the shower head, or connect it back into the shower riser above the valve.

hj said:

The valve body to the shower riser is the restriction, which is why I install my shower valves inverted when the valve's design allows it. (Moen is one of the few it cannot be done) Otherwise, I pipe the bottom, (tub), outlet up to the shower head, or connect it back into the shower riser above the valve.

Click to expand...

What model valve do you use? The PP 08 seem to be restriced on both sides.
thanks