We did a whole house copper repipe and installed a Bosch tankless. We have not been able to get consistent water temperature. It goes from very hot to very cold to hot and is unpredictable. We changed all the pipes (from main street to floor up to the second floor). We did not change the pipes from the floor to the faucets or showerheads. Could this be the problem? We don't believe we have crossovers. But, we still have the old pipes close to the faucets and showerheads. We have not a consistent shower in weeks.

Any suggestions? Is it the tankless water heater? Our contractor says "it will work itself out". I don't think so... :mad:

Since you hired a contractor you should stay on his case until it is resolved, I would not accept an answer that it will work itself out. I never see plumbing issues that fix themselves, well almost never. Do not pay him and you'll see how this helps things work out. If you can reach those pipes I'd cahnge them but I doubt that they are causing your probablems. Do ALL faucets have the same hot water variation or the shower?

When you read the original post you can't help asking:

1) Where are the inconsistent temperatures? All fixtures, shower fixture?

Any suggestions? Is it the tankless water heater? Our contractor says "it will work itself out". I don't think so...
Your contractor is blowing smoke up your skirt. Bob's right! Plumbing problems don't just "work themselves out" they temd to get worse. It's not the older pipes that's causing the problem. One of two things is happening here. Either the plumber left you with a "crossover" or you have a faulty tankless heater. Call the lazy contractor and make hime do the job right. Don't loet him stall you until the warranty, (you did get one didn't you?) runs out. Good luck, Tom