1/2" or 3/4" tub supply...

[Plumbjz]

Pipe size for tub fill question... I have 80 psi throughout house with 3/4" pex supply line to Delta diverter/valve which has all 1/2" connections.

A plumber suggested I run 3/4" from valve to tub for maximum flow/volume. He said volume is improved with 3/4" vs. keeping 1/2" copper on valve outlet. So my question is, would the tub spout flow be increased running 3/4" copper downstream of a 1/2" valve? Thanks for your thoughts.

 

[Twowaxhack]

Run 1/2”. 3/4” would have less friction loss but not enough to notice.

With 80 psi it’ll work great.

If you have the shower valve with integrated diverter with the 1400 series cartridge it’ll flow almost 6gpm at 80 psi.

 

[Twowaxhack]

The 17 series will give you another gallon per minute. Up to 7 gpm.

The 17t cartridge will flow 8.4 gpm.

So the best way to get max flow is to pick a higher end cartridge because they have higher flow volumes.

You’re not going to get anymore water through the pipe than the cartridge allows through the valve.

 

[Plumbjz]

The 17 series will give you another gallon per minute. Up to 7 gpm.

The 17t cartridge will flow 8.4 gpm.

So the best way to get max flow is to pick a higher end cartridge because they have higher flow volumes.

You’re not going to get anymore water through the pipe than the cartridge allows through the valve.

Thanks, Twowaxhack! That makes sense. I didn't catch the logic from my plumber how larger diameter would = more flow after the 1/2 device. Sounds like you know your Delta stuff, too. Yes, we got the17T cartridge, so min. 7gpm with our psi. Thanks for chiming in!