Flow Capacity (Cv) vs. GPM?

[TheGewp]

Are they essentially the same when talking about a thermostatic valve? I am helping my sister repipe her house (1957 with original galvanized supply) and want to make sure we don't make the GPM worse with a valve that's too restrictive. Planning to install one for the whole house, rather than just the tub. Thanks!

 

[TheGewp]

Follow-up question, what is a normal GPM for a tub faucet?

Also, am i missing anything in this rough plan? The current galvanized supply has no expansion tank or anti-scald. Thanks!

 

[Sponsor]

 

[Reach4]

Seems good to me. You can run real hot to the dishwasher and washing machine if you want, and if it is easy enough to do. Otherwise you can run tempered water.

5 to 6 gpm is fairly typical for a tub spout, I think.

 

[TheGewp]

Seems good to me. You can run real hot to the dishwasher and washing machine if you want, and if it is easy enough to do. Otherwise you can run tempered water.

5 to 6 gpm is fairly typical for a tub spout, I think.

Most of the valves i'm seeing are pretty low Cv, which i'm finding is basically the same as GPM in a household system. The Honeywell i have been looking at is only 3.9 Cv. I'm concerned that will be a noticeable difference from the current supply. I dont have any experience with the thermostatic valves, all the houses i've worked on have been too old to have one. Is it pretty common for them to have a 2.5-4GPM flow? Or do they install the more expensive units that get 7+GPM in newer homes?

 

[Reach4]

I don't even know what Cv is.

 

[TheGewp]

I don't even know what Cv is.

It's listed as Flow Capacity in the specs of the valves i'm looking at. Since posting i have found that Watts seem to have a decent GPM for the same cost as the Honeywells.