No Hot Water in one Bathroom

[DG3299]

At the house there is a 75 gallon gas hot water heater, with a recirculation system for instant hot. The problem is in the last bathroom on the 3rd floor there is no hot water when the recirculation pump is on. All the rest of the bathrooms and sinks have hot water. If the recirculation pump is turned off the water gets warm, but not hot. We are pretty sure that the cold water line is either tied to the cold line or the recirculation line because if you turn off the hot water completely you get cold water out of the hot taps. This is not an entirely new problem, since the house was built in 2002 there was a problem with the hot water in that bathroom, especially the shower. At that time there was a different hot water heater, and the water in the shower would get warm for 1-2 minutes, get cold for 1 minute, and the hot for 1 minute, and then be cold the rest of the time. We have shut off the hot and cold valves to each shower to make sure they weren't the problem. Is there a way to narrow down where the cross might be? is there a way to find the crossed line without tearing down all the walls? We are at a loss for what to do to fix this, and any suggestions you have would be greatly appreciated. Below is a timeline overview of what happend and what we tried.

1. Original problem, started upon move into new house. The hot water in the MBR Shower is hot for 1-2 minutes, then cold for 1 minute, then hot for 1 minute, then cold for the rest of the shower. All other fixtures have hot and cold water.
2. Thought that the mixing valve was the problem so it was replaced. That did not fix problem
3. Problem persists with no change, new thought is the lines are crossed because if you turn off the hot water completely, there is still cold water coming out of hot water taps.
4. Hot water heater breaks.
5. New hot water heater installed.
6. No hot water in MBR shower or sink if the recirculation pump is on. If it is off there is hot water in sink but the water only gets warm in MBR shower. Owner does not want to leave recirculation pump off, as he doesn’t want anyone to have to wait for hot water.
7. Any Ideas on how to narrow down where the crossed line might be, find the crossed line without ripping out all the walls, or any other suggestions?

 

[Smooky]

Pictures of the plumbing at the hot water heater so that the lay out of the plumbing can be seen, might help. Pictures of the area where the recirculating pump is located and the mixing valve might help too.
Is there a separate return line or is the cold water line the return line? Are there backflow preventers installed in the system and if so where?

 

[Sponsor]

 

[DG3299]

I will try to get pictures of the Hot Water heater tomorrow, both the old setup and the new setup. Don't have access to the pictures right now. There is a backflow outside for the meter and some check valves along the way. I have uploaded the drawing for the house incase that might help.


If you want you can PM me your email and I can send the drawings over. Not sure if they are too small to see, and I am not sure if there is any file size limit on PM messages.