Kohler Hint deck mount tub faucet with 3/8" copper

[tpsmith82]

So my plumbers brought to my attention something regarding the tub filler we had bought from Kohler. The model is Kohler Hint K-97070-4-BN. This faucet is listed on the Kohler website as having a 11 gpm flow rate, but our plumber thought this was not going to possible given it has 3/8" copper inlet for cold and hot ( has a 1/2" copper to faucet). His logic seems pretty sound in that the things I read online regarding flow rates for given diameters of copper pipe dont come anywhere near 11 gpm. So my querstion is, what gives? Will this faucet supply 11gpm? I did call Kohler and they seemed to reiterate that it will supply 11 gpm at 45 psi.

A couple of other notes....I have requested the supply lines to the thermostatic mixing valve (Watts 3/4" ID mixing valve) be 3/4". Then the mxing valve outlet will be 3/4" but then need to be reduced to 3/8" to connect to the Kohler faucet. We are on a well, and in the past have had seemingly good pressure.

 

[Reach4]

I have not been able to find what the supply inlets are. Could it be you are saying they are 3/8 compression, as might be used on a kitchen faucet? (9.525mm diameter on the outside threads)

"3/8 copper" should be plenty big.

Copper Pipe Size Chart | OD, ID, Wall Thickness & Tube Sizes

Explore our copper pipe size chart with OD, ID, and wall thickness details for Type K, L, M, and DWV copper tubing. Use this copper pipe OD chart to compare tube sizes for plumbing and HVAC applications.

www.petersenproducts.com

Often people, when referring to 3/8 compression, as might be used on a kitchen faucet. (9.525mm diameter on the outside threads). That is for much smaller stuff than type K, L, or M 3/8 copper, which is over 3/8 ID.

 

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[Breplum]

Yeah, I agree with your plumber that flow will be way lower than you desire for a big tub. Of course it is easy to bench test to see results into a bucket.
The small ports within the ceramic cartridge will add to the lower flow as well.

 

[tpsmith82]

I have not been able to find what the supply inlets are. Could it be you are saying they are 3/8 compression, as might be used on a kitchen faucet? (9.525mm diameter on the outside threads)

"3/8 copper" should be plenty big.

Copper Pipe Size Chart | OD, ID, Wall Thickness & Tube Sizes

Explore our copper pipe size chart with OD, ID, and wall thickness details for Type K, L, M, and DWV copper tubing. Use this copper pipe OD chart to compare tube sizes for plumbing and HVAC applications.

www.petersenproducts.com

Often people, when referring to 3/8 compression, as might be used on a kitchen faucet. (9.525mm diameter on the outside threads). That is for much smaller stuff than type K, L, or M 3/8 copper, which is over 3/8 ID.

Well the 3/8 copper "inlet" that I'm referring to is the supply to the faucet valve. So plumber will hook up the Uponor PEX hot and cold to the 3/8 hot and cold "inlet" to the faucet valve. When I measure the copper it's 1/2" OD and looks to be type L copper.

I tried the link you provided, but not sure how you're coming up with it should be plenty big.?

 

[tpsmith82]

Yeah, I agree with your plumber that flow will be way lower than you desire for a big tub. Of course it is easy to bench test to see results into a bucket.
The small ports within the ceramic cartridge will add to the lower flow as well.

Any idea why Kohler would be listing it far higher then?

Also, I like your idea of testing, but curious how I could do that now given I'm a ways off from actually installing the faucet. We are just at rough stage and it will likely be 6 months or more before I install the faucet. We hired the rough plumbing for this master bath, but I'll be doing the final plumbing.

 

[Reach4]

Well the 3/8 copper "inlet" that I'm referring to is the supply to the faucet valve. So plumber will hook up the Uponor PEX hot and cold to the 3/8 hot and cold "inlet" to the faucet valve. When I measure the copper it's 1/2" OD and looks to be type L copper.

I tried the link you provided, but not sure how you're coming up with it should be plenty big.?

I am saying that I think 0.403 ID for hot and 0.403 ID for cold should carry 11 gpm.

When people hear "3/8, they are usually thinking of 0.375 OD, and maybe 0.3 ID. So 0.403ID has about 1.8 times the area as 0.3ID.

Using https://irrigation.wsu.edu/Content/Calculators/General/Pipeline-Pressure-Loss.php it says that a 0.4 inch ID pipe a foot long carrying 11 gpm, would have a pressure drop of about 3.1 psi.

 

[Breplum]

just hook up to a hose bibb with adapters and say, a washing machine hose or garden hose to run the faucet into a bucket.