Why does the hot water run cold at less than 'full throttle'?

Question

I'm as environmentally conscious as the next American (probably not very) but here's an example: I like to rinse dishes that I've just washed in a stream of hot water as this works best for drying. I would like to run the faucet at a trickle, as that's all I need to rinse off soap and put onto the drying rack. But if I run the hot water at a trickle, it is COLD, like 65 degrees F. Opening up the valve fully results in hot water.

Conversely, the cold water tap gives lukewarm water (85-90 degrees F) unless it is opened fully. Both these behaviors persist over time, so it does not seem like it's just room temperature water in the lines. This particular dwelling is also equipped with hot water baseboard heat and recirculating pumps for the hot water lines, which I thought was to avoid this sort of thing.

Is there something wrong with the recirculation pump, where it's forcing backward flow when not overcome by a higher volume due to a fully opened tap? That's the only thing I can think of, I'm stumped. I should also note that this place is a rental, so I will need to get the landlord to fix this, but he's not very, er, mechanically inclined...so if I present the problem in a nutshell with proposed solution, hopefully it will get fixed. Also the fact that we actually have hot water and plenty of it mitigates against action. I just would like to stop wasting so much hot water!

Answer 1

Many new kitchen faucets use a single arm and a cartridge to control how much hot vs. cold water is released through the fixture. Sometimes, the cartridge can go bad as it wears out, causing the mixing process to not work correctly. Shower controls use a similar system. You may be able to get your landlord to replace the cartridge (a simple process for most major brands), solving your problem.

You might also try balancing the hot and cold water using the water shutoff valves under your sink. You can open the hot water valve all the way and then turn the cold water valve down some. This might help if you have significantly more cold water flow vs. hot for some reason.