OK... this is a weird issue. I have a dedicated recirc line with a pump and a timer that I only run an hour a day or so in the morning, due to energy costs of heating the water. The problem I am having is that when I am not recirculating the water, the master shower and master tub only get lukewarm at best, unless I turn on one of the bathroom sinks. Once a bathroom sink is on (which is farther down the loop than the shower), then the shower gets hot like it should, and the water coming out of the faucet is cold. (The tub never gets hot however because it is the last stop on the loop) However, once the recirc pump is on, everything, including the tub, works well. One thing that I was wondering is my kitchen sink took forever to heat up so I had the plumbers come and patch a line through the loop, and I wonder if this is bypassing the Watts valve and allowing the water to backup through the loop so the cold water that is in the hot line is being mixed with the hot freshly drawn. However I could not feel any heat going back through the pipes, and I have no idea why multiple outlets would affect anything. Is this confusing enough? Any help would be appreciated!

To me it sounds like you need to install a check valve on the line from the pump to the water heater. I think when the pump is off the water is coming out of the water heater backwards through the pump and to the faucets that are only getting cool water. A check valve would stop the backflow of water but still let water through when the pump is on.

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Originally Posted by letmetellu

To me it sounds like you need to install a check valve on the line from the pump to the water heater. I think when the pump is off the water is coming out of the water heater backwards through the pump and to the faucets that are only getting cool water. A check valve would stop the backflow of water but still let water through when the pump is on.

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There already is a check valve between the pump and the waterheater (it says Watts on it and arrow is pointing down towards the waterheater on the return line... at least I think that is the valve. I am by no means a plumber... or even remotely handy for that manner). I think the water still could move backwards through the loop though due to the loop patch, but I would assume that if that is the case, hot water would soon follow backwards... but I am finding no signs of that. The return line still feels ice cold to the touch (unfinished basement) after 20 minutes or so of running hot (that comes out lukewarm) water in the master shower.

I am not sure what you are talking about when you mention the loop, but if the check valve is installed and it is the right type valve and installed in the right position, no water can get out of the water heater.
You said something about hot water should soon follow backwards. When water comes out of the bottom, and I a assuming that your return line is in the bottom os the heater, it will be hot for a few minutes and it will gradually get cooler till it is completely cold because of the way a water heater is designed. There is a tube in the heater that takes the incoming cold water to the bottom of the heater so that it does not mix with the hot wanter in the top of the heater.

I could be way wrong, but what I am thinking and the only thing that make sense is that hotwater is coming out of the waterheater correctly, but it comes to the T halfway through the loop where the shortcut was put in to the kitchen, so the hot water splits and goes both ways through the T. Since there is no valve after this shortcut, I think water can go either way. Since the water already in the pipes is cold, and since the water that chooses to travel through the longer option via the T takes a lot longer to get hot, the cold mixes with the hot and I get warm. I would be convinced if I could tell that hot was actually moving backwards through the T. I can't find any evidence of this, and can't think of anything else that would cause my problem.