Ihave a brand new kohler K-10411-cp that I just installed. there is very low cold water flow and better hot water flow. Checked the supply valves and all are working OK. What's wrong?

Turn off the hot & cold water supply lines at the shut-off valves.

Yo need to use the correct replacement cartridge for the faucet you are fixing

The cartridge replacement procedure requires using food grade silicone lubricant around the base of the new cartridge and around the threads of the bonnet.

Then you must properly align the 2 bumps on the bottom of the cartridge with the inside body of the faucet.

Insert and tighten down the bonnet that holds the cartridge in place to where it is snug- do not over tighten the bonnet!

Then reinstall the trim piece and lever.

Slowly, fully open the hot and cold water shut-offs and check for leaks at the shut offs, sink handle, and spout.

If you are using the Watts brand floodsafe supply lines, turn the hot and cold water shut-offs, on slowly. Rapid flow and pressure may activate the floodsafe valve within the supply line, causing little to no water flow to the faucet.

Refer to the manufacturer's recommendations for back-flushing/descaling to flush out mineral deposits and build-up in the heat exchanger. You can check to see if this is a problem by comparing the full cold water flow with full hot water flow at the faucet. If the hot water flow is significantly slower than the cold then the heat exchanger is likely clogged with deposits and will not transfer heat sufficiently. If the flow is good then the heating element(s) maybe defective.

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First turn off the shut-off valves and remove the Forte faucet inlet hose from the cold water line. Then put a temporary inlet hose on that shut-off valve. Test how much water flows into a bucket when you open the valve. Assuming that you had good flow from the cold water shut-off valve through the supply hose, a trickle flow on one side suggests the cartridge plunger (mixing valve) or the inlet hose is blocked or damaged. Since this is a new unit, I'd recommend you replace the faucet. The best option may be to take it to the place where it was purchased (depending on the return policy).

I hope this helps and wish that I had better news for you.

Cindy Wells

Should be valves under your sink for the faucet. #1
Make sure they are opened up enough.
If either device is new, they should support this issue.
Old plumbing can also cause this. Build up in the lines.
They can only be replaced to fix. Some water heaters have adjustable valves, make sure if you have them they are opened as needed. Remember, too low flow can cause over heated water.

Cartridge may be 180 degrees off

If the faucet was working before and then just stopped, it is the mixing valve or a clogged supply line.
turn the water off and remove the mixing valve. Turn the water on and see if you have good flow from both hot and cold ports inside the faucet.
Caution- this procedure can get messy, close the shower curtain or door.
Call Kohler and ask for a new mixing valve for free.

If this is a new installation and has always beenj this way, then I would suspect that there may be an obstruction in the cold water line leading to the valve. Or something stuck in the valve at the point where the cold water is connected. If someone has worked on thius valve recently , then I would suspect that they got the valve cartridge in backwards, If the catridge is not placed in the valve correctly the opperation is messed up.

Probably some pipe rust clogged the exit.
If u have pretty low pressure on one or both, hot and cold water, try keep force closed by hand the water exit at shower pipe, then start both cold and warm water gradually as much as u can keep it closed with the hand.
The pressure of the water will try "escape thru the clogged pipe and hopefully unlock that debris or rust!
The hot water pressure going back thru the cold water pipe might unclog that debris.
Just a simple fix which many times works as a charm..
Otherwise if this is not fixing, try close both water from main service valve.
Then unscrew the secondary shower valves and manually clean them or replace if very damaged.

Just had this same thing, on this exact faucet. If you still have the manual, it has instructions on how to rotate the valve for back to back installations where one shower has the hot/cold reversed. Our contractor got ours in backwards the first time and I had to call and have them come out and rotate the valve this morning.

Hi pglaw,

My best guess is the supply valve for the hot side isn't open all the way. This valve is right on the valve and is accessed by taking off the front cover plate. This would still allow the pressure balancing valve to let water through but then you would have a small flow on the hot side.

If this isn't it then then cartridge is bad.

Please rate this response and good Luck,, phil