I have a puzzle:
The water heater in a small building was too hot — scalding. Turning the thermostat down to warm or even vacation didn't seem to make a measurable difference. We were about to have someone out to replace the thermostat.
The gas water heater is only one year old. This building is small. Four bath sinks, one urinal, 3 toilets, one kitchen sink.
We turned off the hot water valves in the bathrooms sinks for safety. We then observed that two sinks in ONE bathroom had just a trickle of cold water (each with their own shutoff valves). Hot water (when it was enabled) seemed to have full flow. Cold water in ALL other locations in the building seemed to have full flow.
I scratched my head and didn't put the two things together – asked someone else for their help and he noticed a hose bib outside had only a trickle and that it was part of the shut off valve for the building. So he completely opened the shut off valve.
We regained cold pressure in the bathrooms. We also saw a reduction in the hot water temperature. (I also verified that when turning the thermostat that the thermostat clicked over at the low temperature as I passed it — which is what one wants.)
At first I assumed there must be two water entrances to the building, which would explain the full flow in some locations but not others (need to confirm there isn't a 2nd entrance. It seems so odd I'm having doubts about that theory.)
Note, this shutoff valve is also right next to the bathroom sinks in question.
I'm trying to come up with a model in my head how all of these things could be related.
Pressure built up in the water heater which pressurized part of the system? Why only part? Air in the water heater? But I never get any popping at the taps. The pressure release valve works fine.
Is there a coherent explanation of this behavior?
Best Answer
The final piece of the puzzle reveals what was going on.
What I thought was a 2nd or 1st building shutoff was a shutoff outside the building that only shuts off those two specific bathroom sinks' cold water supplies.
Why!? Who knows! It's an old building.
But that explains why those two taps were too hot and why none of the other fixtures in the building were affected.
Another factor was that I was using the kitchen sink faucet to test the water temperature, but those are probably not anti scald.