I am unable to control the temperature in my master shower. Water is either scalding hot or goes cold. My water heater is a tankless Bosche. This problem has been going on for several years which I can somewhat mitigate by changing shower heads, but it does not work for long. Problem had vexed multiple plumbers. Initially, the shower diverter valve was replaced. Did not work. Later I replaced the whole fixture in the shower. No solution. No other fixture in the house is affected by problem, leading me to believe the water heater is not the problem. I found a bulletin released by Bosche on an old, old water heater sales site that gave possible reasons for the problem, one being a crossover of cold water into the hot water stream causing a backup to the heater, thus causing it to fire incorrectly, if I understood right. Sure enough, when the hot water is turned off at the heater, cold water still streams out of shower when turned on hot. However, plumbers still are not sure how to fix it. Plumber wants to replace cartridge again (which I think is a waste of time) since it has been done twice, the move on to replacing the washer solenoid. I have read washer solenoid could problem, but I do not know how to prove it. Also, when I cut off valves to washer, crossover still occurs. Does anyone know how to test if washer machine is causing problem, or does anyone else have any other brilliant ideas of where a crossover can occur?
Cross Connection Crossover in Master Shower
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look and see if showervalve was installed with the shower head as spout and spout as shower head
valve has either arrow pointed up or H C SHR
valve has either arrow pointed up or H C SHR
Do you have any 2 handle faucets in the house?
Shut off cold supply to water heater.
Open hot only on a 2 handle faucet.
No 2 handle faucets??
Then shut cold angle stop off to a faucet so you know 100% that when you open that faucet you will only get hot ( if Hot was on at heater )
You should have ZERO water flow from that faucet. If you have water flow, then YES you have a cross over some where.
Let the faucet run. make sure the drain can take it before you walk away.
Now go listen to the other fixtures ( Closed ) for water passing through them.
Older style MOEN's are known for crossover problems but mostly when the hot and cold systems are unbalanced.
The auto washer. turn off the supply valves and disconnect the hoses to make sure the valves do shut off 100%.
Shut off cold supply to water heater.
Open hot only on a 2 handle faucet.
No 2 handle faucets??
Then shut cold angle stop off to a faucet so you know 100% that when you open that faucet you will only get hot ( if Hot was on at heater )
You should have ZERO water flow from that faucet. If you have water flow, then YES you have a cross over some where.
Let the faucet run. make sure the drain can take it before you walk away.
Now go listen to the other fixtures ( Closed ) for water passing through them.
Older style MOEN's are known for crossover problems but mostly when the hot and cold systems are unbalanced.
The auto washer. turn off the supply valves and disconnect the hoses to make sure the valves do shut off 100%.
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I have done the crossover test where I cut the cold water supply to the heater and opened all my hot faucets and left the cold closed. Every faucet stopped pouring water except the master shower. I let it pour for over 20 minutes to just to be sure. The master shower is not two handles. The shower located very close to the heater, probably less than 5 feet through a wall. I will disconnect the washer machine hoses instead of just turning off the valves and try again either tonight or tomorrow. Does there happen to be any chance of a crossover at the valves the washer machine hooks up to as oppose to it being the washer itself?
most washer have 2 separate valves. if you have one valve with a single lever that you connect the 2 hoses to like the picture below, IT IS NOT a mixing valve. water does not pass between the hot and cold. basically 2 valves with a common handle.
What you did is not how I said to do it. read it again.
By opening all the faucets you defeat the purpose of listing to the crossover in the other fixtures. You are looking for crossover in the other fixtures while they are turned off. Even the shower. The only one you have on is the two handled faucet ( hot only ) NO chance of crossover in a 2 handle faucet unless both the hot and cold are turned on. You will be able to here the water flowing through the closed fixture if it has crossover.
I guess in theory an autowasher solenoid can cause a crossover but I have never seen that happen before. Not to common from my experience.
Good luck
What brand and model of shower valve do you have. Is it a Pressure balanced or thermostatic balanced?
What you did is not how I said to do it. read it again.
By opening all the faucets you defeat the purpose of listing to the crossover in the other fixtures. You are looking for crossover in the other fixtures while they are turned off. Even the shower. The only one you have on is the two handled faucet ( hot only ) NO chance of crossover in a 2 handle faucet unless both the hot and cold are turned on. You will be able to here the water flowing through the closed fixture if it has crossover.
I guess in theory an autowasher solenoid can cause a crossover but I have never seen that happen before. Not to common from my experience.
Good luck
What brand and model of shower valve do you have. Is it a Pressure balanced or thermostatic balanced?
I have a single handle so I think that means a pressure balancing shower. It is a Delta Windemere Chrome Single Handle Shower Valve according to my plumber's receipt.
I guess I initially thought that if any other fixture had a crossover in it it would have failed the test I mentioned. I did the test leaving my kitchen sinks hot water on, all the rest of the fixtures in my house off. I did not hear water flowing through any of them. I did randomly discover that when my wife turned on a master bathroom faucet while I was doing the test, the cold water flowed out the kitchen's sink's with only the hot faucet on. Not sure what that proved. I cut both faucet's valves completely off but it did not stop the crossover occurring in the master shower.
I guess I initially thought that if any other fixture had a crossover in it it would have failed the test I mentioned. I did the test leaving my kitchen sinks hot water on, all the rest of the fixtures in my house off. I did not hear water flowing through any of them. I did randomly discover that when my wife turned on a master bathroom faucet while I was doing the test, the cold water flowed out the kitchen's sink's with only the hot faucet on. Not sure what that proved. I cut both faucet's valves completely off but it did not stop the crossover occurring in the master shower.
Okay. So let's be clarify something.
When you had only the kitchen hot open, was the cold supply off to the water heater and no water coming out of the kitchen? That is important.
That means you do not have a crossover between the hot and cold system when every thing is closed. If cold water is flowing from hot side of kitchen when the supply to WH is off and no other fixtures are on then you have a crossover or the valve to isolate your WH is leaking by.
A single handle fixture does not make it a balance valve. I'll check into yours later. Have to go for now. any mixing valve can allow water to pass from cold to hot or hot to cold system when opened if one of the systems has more pressure than the other. so if you have Zero pressure on the hot and you open a mixing valve the cold will flow into the hot and back to the kitchen faucet like you experienced.
When you had only the kitchen hot open, was the cold supply off to the water heater and no water coming out of the kitchen? That is important.
That means you do not have a crossover between the hot and cold system when every thing is closed. If cold water is flowing from hot side of kitchen when the supply to WH is off and no other fixtures are on then you have a crossover or the valve to isolate your WH is leaking by.
A single handle fixture does not make it a balance valve. I'll check into yours later. Have to go for now. any mixing valve can allow water to pass from cold to hot or hot to cold system when opened if one of the systems has more pressure than the other. so if you have Zero pressure on the hot and you open a mixing valve the cold will flow into the hot and back to the kitchen faucet like you experienced.
CW was off to heater, kitchen hot was open and no water was running out. It was a two handle faucet. Thanks for the explanation on the single handle bathroom faucets. I thought I might be on to something but then after work I checked all my single handle faucets and noticed they cause cold water to back up into the hot out the kitchen sink. Then I thought it might be normal and you confirmed it.
I starting the there is no crossover at another fixture. I've ruled the washer out by disconnecting and every other fixture passes your test and the one I originally tried by just opening the hot valve of each one. I have also shut off every fixture's supply valve and water still leaks out my shower's hot with the CW off to heater. The overall problem is that in the four years I have owned my house I have never been able to control the water temp in my master shower. It comes out scalding hot, and then will go cold, then back to scalding hot. I take short showers. Plumber 1 replaced the mixing valve. No avail. When he took the head off, we had complete control of temp. So I replaced head with one with more flow rate. Worked for about a month. I have replaced head several times with several different types. They solve problem for about a month. Also discovered water pressure in house too high. Had flow reguator valve replaced. Plumber told me that wouldn't fix it and he was correct, but I needed it anyway. Plumber 2 replaced whole fixture. No fix. Meantime I finally found a service bulletin on a random plumber's supply site from Bosche that mentioned temperature fluctuation problems with my model tankless water heater and possible solutions and I found my shower failed the crossover test. Mentioned it to second plumber and now he wants to replace washer solenoid. He works at a very good company that charges a lot, but trains there employees very well and he actually discussed this problem with several of his coworkers and boss before mentioning that solution. This is all getting expensive. In the end, it may not even be the crossover causing the problem. Should cold water getting into the hot line cause scalding water anyway? Other shower and all other fixtures control temp fine, making me think water heater is fine. Could a shower being so close to water heater (like 5 feet) cause a temp problem? I really appreciate the help, but if nothing else really jumps out you don't have to keep writing back. When I save up some money I can get a plumber back out to throw money around at other fixes that probably won't work.
I starting the there is no crossover at another fixture. I've ruled the washer out by disconnecting and every other fixture passes your test and the one I originally tried by just opening the hot valve of each one. I have also shut off every fixture's supply valve and water still leaks out my shower's hot with the CW off to heater. The overall problem is that in the four years I have owned my house I have never been able to control the water temp in my master shower. It comes out scalding hot, and then will go cold, then back to scalding hot. I take short showers. Plumber 1 replaced the mixing valve. No avail. When he took the head off, we had complete control of temp. So I replaced head with one with more flow rate. Worked for about a month. I have replaced head several times with several different types. They solve problem for about a month. Also discovered water pressure in house too high. Had flow reguator valve replaced. Plumber told me that wouldn't fix it and he was correct, but I needed it anyway. Plumber 2 replaced whole fixture. No fix. Meantime I finally found a service bulletin on a random plumber's supply site from Bosche that mentioned temperature fluctuation problems with my model tankless water heater and possible solutions and I found my shower failed the crossover test. Mentioned it to second plumber and now he wants to replace washer solenoid. He works at a very good company that charges a lot, but trains there employees very well and he actually discussed this problem with several of his coworkers and boss before mentioning that solution. This is all getting expensive. In the end, it may not even be the crossover causing the problem. Should cold water getting into the hot line cause scalding water anyway? Other shower and all other fixtures control temp fine, making me think water heater is fine. Could a shower being so close to water heater (like 5 feet) cause a temp problem? I really appreciate the help, but if nothing else really jumps out you don't have to keep writing back. When I save up some money I can get a plumber back out to throw money around at other fixes that probably won't work.
Although I don't have any constructive input for you, I can tell this is very frustrating for you. Hang in there, and please keep us in the loop as to what eventually solves this dilemma.
