Isn't the PRV spring loaded? Once the pressure is released, it should close and seal. In this case, when I flipped the test valve, the "plunger" pulled out but was not pulled back in. I think the spring is shot. I doubt its actualy due to high pressure, more likley the PRV has failed on its own. The only other thing could be the supply side pressure reducer failed and is allowing to much pressure into the system. Unfortunatley, there is no pressure gauge on the system to check. I may place a pressure gauge over a boiler drain and open the drain just to check the pressure is OK. I can isolate the boiler from the zones so repair is not an issue for me. Just a threaded 3/4 connection, so thats easy.

I have to agree with Homebound, under the general heading of "the toilet still leaks" there are a number of possibilities. You stated that you changed the flapper and the flush valve so I am assuming that you mean the water level in the tank is slowly dropping and causing the fill valve to repeatedly open momentarily. If you changed the flush valve a new flapper should have come with the flush valve kit, so for the moment we can rule out the possibility that you have the wrong flapper. There was a time when the flappers were all the same and we just carried a box of "Corky's" on the service truck, but with the advent of low-flow toilets they had to slightly redesign the flappers and flappers are now rated by the GPF (gallons per flush). (They now make universal flappers that have a rigid plastic mount and the rubber ball can be rotated on the mount to adjust for the GPF) There are primarily two different methods of mounting the flappers. Most flappers have two arms that extend to the standpipe and there are holes in the end of the arms on the flapper that fit over cast plastic fingers extending off either side of the standpipe. Check the holes in the rubber arms on the flapper to make sure there is no excess rubber in the holes that might prevent the flapper from freely swinging on the fingers, then check the plastic fingers to make sure there is no excess "mold Sprue" plastic on the fingers that would interfere with free movement of the flapper. There is a style of flapper mount where there is no fingers on the standpipe. Instead the flapper has a molded rubber ring that fits around the standpipe. This type of mount can be a real PITA to adjust because if it is even slightly too high it keeps the back of the flapper elevated above the flush valve seat, and if it is slightly too low it puts a downward force on the back of the flapper which causes the front of the flapper to be raised slightly. Personally i try to avoid that type like the plague. Lift the flapper and run your finger nail around the top mating surface of the flush valve. If you feel any slight bumps use a piece of 600grit emery paper to smooth off the seating area. Check the length of the flapper lift chain from the flush handle. Properly there should be 2 links of slack in the chain. (The flush handle lift arm should be able to move about 1/4 to 3/8" before it begins lifting the flapper.) If the chain is too tight it can hold the front lip of the flapper above the flush valve seat. If the chain is too long it will produce a sluggish flushing action. Check the tank water level. In the inside wall of the tank you will find a "Water Level" index mark either painted on the tank wall or perhaps embossed into the ceramic casting of the tank. If the water level is too high or too low adjust the flush valve float. (The index should be about 2" below the top of the standpipe.) Check the trap primer line, which is the small diameter plastic line that runs from the fill valve to the top of the standpipe. Make sure that the line is positioned so that it cannot interfere with the free movement of the flush handle chain. At this point you have covered all the common problems associated with water leaking from the tank to bowl and causing the fill valve to repeatedly cycle. If this has not resolved your problem please give us more detailed information about the type of leak your having and we can offer additional information.

Quote;"I much prefer using ball valves in applications where they are to be in either the fully on or fully off position. In in-between positions, they tend to 'sing' (and I don't favor their taste in music)." Gate valves & ball valves are defined as "Full Bore Valves" and they should never be left partially closed. They are intended to be either fully open or fully closed at all times, no exceptions. Leaving a full bore valve partially closed can and will lead to a number of other problems on the line including an increased risk of pin-holes on the downstream side of the valve. I prefer ball valves for 3 reasons. 1. A ball valve is constructed of a round ball with a hole drilled through it equal to the diameter of the pipe. When the valve is open the interior of the valve is almost equal to the interior of the pipe so there is no associated turbulance or friction as the liquid flows through. 2.Generally the ball is suspended in a nylon or teflon bearing pad between the ball and the valve body that primarily serves as a seal but it also serves as a bearing to make turning the ball easier. 3. The handle should be attached so that it is in the same direction as the hole through the ball. When installed in that manner you have a good visual indicator of when the valve is open or closed. When the handle of the valve is parallel to the pipe, the valve is open, and when the handle is at right angle to the pipe, the valve is closed. It is almost impossible to look at a gate valve and tell if its open or closed, unless or course, you elect to use OS&Y(outside stem & yoke) gate valves, but I doubt if you will ever see an OS&Y gate valve in a residential structure because they are typically only used on lines that are 3" and greater, and OS&Y valves are extremely expensive.

I just don’t have time to fix it. When I called the foreman, he said that it was necessary to change the valves ... I had to look for the best industrial valve manufacturer usa. I spent quite a lot of time comparing reviews of different companies (it's a pity that I didn't think of creating a topic on the forum and asking you). Anyway, now I don't have this problem. The only negative is that the accident site dries up for a very long time. Maybe there are some ways to speed it up?