This is a weird one. I recently changed my bathroom faucet with a replacement faucet system from Kohler, which was under warranty.

When I reconnected everything, we can't get hot water out of the one handle faucet, unless the toilet is flushed. The water pressure is also low.

I've read that the toilet flush drops the cold water and thus the hot flows through, and / or that the drop in cold water pressure allows hot water to push past any built up sediment.

However, I have been turning off the cold water supply and the water that comes out is still cold, then we flush and it turns hot and then back to cold again.

Kohler sent a new cartridge, which I've just changed, I've flushed the hot hose (have read that I should also flush cold), I've checked the water coming from the wall, which gushes out and is very hot.

I have yet to check the faucet spout screen for sediment, which could be part of the problem, but even if it has built up sediment, why would the water be cold when the cold inflow is shut off?

The water inflow is from the other side of the apartment (it's in a condo building), so it has always taken a bit of time for the hot to make it to the taps, but this is clearly something different.

Any insight would be very much appreciated, thanks!

Looks like you have a crossover somewhere, cold water flowing into the hot water line. Usually happens at a shower valve. The hot water pressure might be lower than the cold water pressure in your high rise.
As I understand it, you have a single handle sink faucet. Even when you turn the cold water supply to the faucet off under the sink, the water coming out of the faucet is not hot. Is that right?



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