I am having problems with my shower hot water. If I turn on the water in the shower (a single lever mixer faucet) it takes forever to heat up. If I turn on the bathroom sink faucet (one lever for cold and a separate lever for hot) at the same time as the shower ,the shower gets hot quickly. If I turn off the sink faucet the shower gets cold quickly. I have a second sink in the bathroom that reacts the same way the shower does.

I have a recirculating pump on my water heater which no longer works. Could the pluming set up for this pump have something to do with my problem? If not what would cause this problem?

I would have the pump repair or replace and the circulating system put back in operation. If that doesn't clear the problem click on back and let us know. Good luck, Tom

How long has the recirculating pump been down? If it is a long time, then I'm inclined to think that the issue is not at the pump, but more likely, you have a cross connection somewhere where a single handle valve (including the shower valve) has lost its ability to balance temperature/pressure and will need to be repaired to resolve your issue.

I would start by shutting the hot water shut off OFF under each sink with a single handle valve or faucet and then try the shower again. If the problem is resolved, then you need to open one hot shut off valve at a time until you see the issue return. When (if) the issue returns, you'll know which valve or faucet needs to have its parts replaced...;)

Note that single handle valves/faucets can also include any single handle washing machine valves, any washing machine with two handles supplying water to the washing machine (simply close the hot shut off valve), or any other place, such as an outside faucet that may have a mixing valve installed to allow for warm water to the outside faucet, etc...

Finally, shower valves are notorious for NOT having shut off valves to isolate the valve, so if no issue shows up after you go through all steps then the issue is probably with the balancing spool of your shower valve itself, OR with the recirculating pump and the CHECK VALVE at the pump...;)

Check these things and then post back, OK?

Mark