I own a 10 room bed and breakfast. Over the years I have remodeled all the bathrooms and installed PB values in all. Over half the showers, some are double showers, have the normal K-304 Kohler valve. I have had no problems with this valve. My plumber used high flow pressure equalizing shower valves on 4 showers that have given me fits,
On an intermittent basis, no cold water is available in the room. The shower is scalding hot in the cold and hot position, the toilet
is filled up with 140 degree water, and the sink has no cold water coming out to the cold faucet. Only scalding water. No, the lines are not plumbed backwards as it is intermittent. What do I do? I remove the valve cover, flow regulator (stem) and PV valve. Shake the PE valve, sometimes open it up and move the piston back and forth trying to see if it is sticking. I usually end up scratching my head, putting it back together again and praying that the problem has miraculously cured itself. Sometimes the problem is fixed. Or not. I have tried other things better left unmentioned but nothing solves the problem.
The town I am in has installed back flow prevention valves between the water main and the house for every home that has an irrigation well for which I am one. It occurs to me that heated water has a higher pressure in a closed system and that possibly higher pressure hot water is displacing the cold water in the plumbing lines, traveling through the shower valve and over to the toilet, or sink, and onward to other rooms as well. What a nightmare when you have 20 people staying over and no one can take a shower or bath because of the temperature issues. This situation has cost us thousands of dollars in unhappy guests and with social media it is a business killer.
Would a expansion tank solve this situation? If so, what line should I put it on? - Before the hot water tank on the incoming cold water line? As an aside, our city has installed back flow prevention valves between the water main and every house that has an active irrigation well for which I am one. I am afraid no plumber i have talked to has a clue on what to do. I have torn out two of the high flow units and replaced them with the cheaper normal ones and they work fine. If you can't come up with a solution I will have to tear out the last two as well. Keep in mind, these are high end showers with valves hidden by tiled walls with the outside walls sitting 35 feet off the ground. I am beyond upset. Why we used high flow valves is beyond me.