1/2 pipes + 3/4 valve

[Adam G]

Because of a miscommunication, I ended up with a 3/4 inch Kohler Master Shower Thermostatic shower valve instead of a 1/2 inch. The plumber has run 1/2 inch pipes in the wall. He said there is no reason to return it and wait for the shipping of the new one as it will make no difference and in fact could result in a slight increase in GPM and no loss in pressure. Does this sound right to everyone? Is there any issue with using a 3/4 inch valve with 1/2 inch pipes?

 

[Terry]

The HansGrohe i-Box comes standard with 3/4" inlets and is normally bushed down to 1/2". The Kohler should work the same way.
Keep the valve, the plumber is right.

 

[Sponsor]

 

[Adam G]

Thank you! Good to hear confirmation!

 

[Adam G]

So the company ended up shipping out the 1/2 valves overnight and they got here in time for the plumber to install on Tuesday. Is it true that I "might even see a slight improvement in GPM" by going with the 3/4 inch valves? Or now that I have them should I just install 1/2inch to 1/2 inch?

The 1/2 valve specs on the website say max of 9GPM and the 3/4 inch says 17GPM. My understanding is that 1/2 copper pipe cant do more then 9GMP anyway. My building does have very good flow. I know my non-renovated bathroom get upwards of 10 GPM.

 

[Terry]

What's the part number on the valves so that we can look them up?

 

[Adam G]

What's the part number on the valves so that we can look them up?

http://www.us.kohler.com/us/Mastershower-XVII-3-4-thermostatic-valve/productDetail/valves/428602.htm


http://www.us.kohler.com/us/Mastershower-1-2-thermostatic-valve/productDetail/valves/428599.htm

PS. I know I am limited on my shower head, though mine is VERY good, but would like to fill the tub up as quickly as possible.

 

[Jadnashua]

The maximum flow on a valve generally increases with a larger valve, given the same design. So, yes, a 3/4" valve will USUALLY have a higher capacity than a 1/2" one. But, to achieve the full capacity, the supply lines to it need to be of adequate size. Using a 3/4" valve with 1/2" supply lines might have a slightly higher volume, but nowhere near as much as if it had 3/4" (or larger) lines feeding it all the way back to the source. The difference in cost for the slight benefit often isn't worth the increased cost of the valve if you can't increase the supply pipes accordingly. It certainly won't hurt except for your pocketbook.