I live in an apartment building where the hot water comes from the heating boiler, and is simply not hot enough for the kitchen sink. It only needs to rise 10 or 15 degrees higher. There is a 20-amp circuit for the garbage disposal that could be utilized. Is there a product that could could be hooked in line and heat the water slightly hotter?

A tankless water heater would be too costly/\. Here's what I would do. If you're going to use that 20 ampm breaker replace it with aa 30 aqnp breaker. I would then purchase a 30 gallon single element water heater and install it in series with the hot water from the boiler connrcted to the cold water inlet and let it fed the rest of the house. Good luck, Tom

Tom, never doubting your expertise but just replacing the 20 amp breaker with a 30 and not knowing the wire ampacity should not be done. Don't know that this could be done in an apartment either. I would get a small under sink demand heater.

Brain,
Most breaker panels are wired at 150 amps, The water heater only pulls 19 amps. Since the disposal feed is already in and the heater feed will be a new installation with heavier wire I fail to see your concern. Regards. Tom

For about $225, you can get a 4 gallon water heater that fits under a sink and plugs into a 110v outlet. Bosch makes one.

Bosch Water Heating GL4 Electric Mini-Tank Under-The-Sink Water Heater

Brain,
Most breaker panels are wired at 150 amps, The water heater only pulls 19 amps. Since the disposal feed is already in and the heater feed will be a new installation with heavier wire I fail to see your concern. Regards. Tom

I did not see a comment about a new service feed. That's why I commented. I concur.