Weird plumbing

We have a recirculating pump connected to our master bathroom. The pump died and the bathroom did not have any hot water. I took the now dead pump offline and now the bathroom gets hot water, but not quite as hot as it used to. Also, the kitchen, which used to have hot water now does not, no matter how long I let the water run. Can anyone think up a scenario to explain this weird situation. Our plumber, who has fixed the pump in the past cannot explain the piping.

This probably is not the answer, but it would not hurt to check the kitchen faucet cartridge if it is one of those one handle jobs.

I had a bad one at an old apartment, and strangely, the kitchen sink worked fine, but because of a closed valve somewhere in the plumbing, since the cartridge leaked, it allowed my toilet to fill with hot water. It is possible yours has failed in a different way.

I can assure you, a fresh BM in hot water will render the entire apartment uninhabitable.

Usually the hot water circulating line comes off the water heater, makes a loop feeding all of the fixtures which require hot water, then tie back into the cold water right before it goes back into the water heater. There might be an expansion tank and a check valve to keep the cold water from going into the hot return line. All I can think of is that your problem has something to do with the check valve malfunctioning. Is it too much trouble to get the pump replaced?

Do you have a two pipe or a three pipe system?
with a three pipe system check the check valve at the pump.
A two pipe system will have an automatic valve near the sink connecting the hot water line to the cold water line. That valve may be staying open.

I am feeling stupid, but now I think the problem might be with the hot water heater. I am concerned that it is only putting out luke warm water. What is the best way for me to check this, and what might I consider to fix it.

open the faucet closest to the heater and let it run until hot, there might be a tap right above the heater.

If you have a garden hose you can connect to the spigot at the bottom of the water heater, run it to a nearby drain and open of the valve. You should be able to tell how hot it is just by how much steam is coming off of it. But, if this water heater is more then 5 or 6 years old and you’ve never opened that valve, then nix that idea, it’s possible that’s there’s so much sediment down there you won’t be able to reclose the valve.

Considering the recirculating pump and the possibility of a bad mixing valve somewhere in the system, I would shut off the cold water valve under each sink and then see how the hot water is at the problem sinks. If it’s cold, it’s likely the water heater. If it’s hot, it’s not the water heater, it’s likely a bad mixing valve somewhere in the system. Start by turning the water on for every sink that has two handles since it’s less likely that they are the problem. Then test the hot water for a few minutes. Then do the same for the other sinks, one at a time until you figure out which one is the problem.
Don’t forget the showers.

A recirc pump is generally not used for any potable water source.

If you have a recirc pump, it is most likely that the you have a furnace that supplies hot water for heating the house in zones, and also has one zone that is valved to a coil in the tank of your hot water heater.

If that is the case, then a failure of the recirc pump will both stop the production of the potable hot water, and also stop hot water radiant heaters from working.

If hot water radiant zones are working, you probably have a bad thermostat or automatic zone valve going to the water heater coil.

Also, if there is a leak in the closed loop system (furnace water), and the automatic makeup water valve isn’t functioning, you just don’t have water to pump through the system, resulting in little or no heating.

I have a hot water circ pump on my water heater, no closed loop system. The water heater is gas fired. The furnace has nothing to do with the hot water. My son has the same thing in his house.

As above, I have a forced gas furnace and a gas hot water heater, both totally separate. The recirc pump is strictly for the master bathroom, at least that is what I believe.

two different types of circulating pumps have been mentioned. the OP seems to be the second by my understanding (IANAP).

if you have indirectly heated domestic hot water (you have a boiler and hydronic heat) then there will be a circulating pump on the loop that goes to the hot water heater. each heating zone and that hot water loop could have its own smaller pump.

there is a case of a circulating pump used in some cases where a faucet is far from the water heater and you don’t want to wait for the time for the hot water to reach the faucet. a small pump keeps an amount of hot water circulating in a loop to at that far faucet to eliminate the wait.

if a plumber who has worked on the system can’t figure it, then it will be a long shot that it might get solved here. though the pumps aren’t that common (IANAP) and it could be beyond that plumber’s experience.