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Volume per minute of water at 50psi through 3/4″ Pipe?
How much water would be pumped through 3/4″ pipe at 50 Psi per minute? I’m trying to run plumbing through a house while maintaining good strong water pressure. I was going to go with a tankless water heater but they’re all only 1/2″ inlet and outlet. I was told a 3/4 would empty a 40 gallon tank in about 98 seconds at 50 psi. Is that true? I already bought 2 100′ 3/4″ rolls of pex pipe. Should I take the hot water roll back and exchange for 1/2″ instead? Thanks
All the 1/2″ pipe will do is give you lower pressure at the far end and thus a less effective shower, slower tub fill, whatever.
It might be true that a 3/4″ pipe with an open end could move 40 gallons in a minute and a half – but none of your fixtures will come close to doing that. Shower heads are supposed to be flow restricted to 2.5 GPM these days. Even if you defeat the flow restrictor it probably won’t do more than 4 or 5 GPM and that would be a very heavy shower. Most tub fill valves aren’t capable of more than 8 or 10 GPM though you can get ones that claim to do 16 or 20 GPM. Most clothes washers are limited by their solenoid valves.
In any case, the 3/4″ pipe can easily serve a fixture or two at the far end of the house and if someone turns on the sink while you are in the shower, the pressure drop will be minimal. With the 1/2″ pipe you’ll start to see issues when multiple fixtures are on.
A lof of people seem to think that smaller pipe equals higher pressure, but it is just the opposite – Bernoulli’s Law.
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