[Archived]

Charles,

Have you confirmed the are no issues with your expansion tank?(air set properly and not waterlogged) That would be assuming there is no check valve isolating the cold supply to the water heater from the expansion tank. If there is disregard as it would have no effect. What youve described is all there is to replacing that valve.

[Deleted User]

I have the same situation with one valve , was just going to do a search for the replacement. I know it has been discussed to make sure to get 75 # instead of household 150# release valve.

Mine is only few years age also.

[Archived]

Mine drips a little after driving awhile but quits once parked no problem

[Andy]

Sometimes you can just open the valve and close it, but you run the risk of a worse leak. I’m always reluctant to remove and replace because they are so tight it’s possible to damage the heater by removing. Years ago I did one and cracked the female threaded casing.

[Corey]

The pressure valve in our water heater failed after just a few years. Found the water heater leaking upon arrival at ETLC and Jeff’s guy replaced it. Then a year or so later we were on the road, stopped at an Interstate rest stop, got out of the coach and there was a a steady stream of hot water pouring your from under the coach … coming out the pressure escape line.

I ordered a 75# valve off the Internet (can’t remember where). Carefully removed the flexible hose and then more carefully removed the valve with a large Crescent wrench; “righty tighty, lefty loosy”. The “old” valve which wasn’t that old had lots of lime on the inside. Put plumbers tape on the threads of the new one and screwed it in by hand. Final tighten with the wrench to get the discharge pointed in the right direction. Reconnected the discharge hose and we were good to go.

Biggest problem is reaching into the water bay to get at the water heater. If you have short arms its a reach. Not a difficult project in my book.

[Archived]

The advice regarding the expansion tank is right on. But those temperature pressure valves will also open on temperature and unless the coolant temperature heating the tank while driving is regulated that almost 200 degree temp will also cause issues.

On every one of my Liberty coaches with the Raritan type water heater I added a solenoid valve in the coolant line to the tank controlled by a thermodisc type thermostat. The benefits of doing that are the coolant flow stops heating the tank when the water in the tank reaches the 125 degree thermodisc set point, and the risk of scalding from the use of hot water after driving is eliminated.

[Archived]

When we replaced the raritan in the Liberty, we opened the valve three quarters of a turn. That valve ( gate type) controls how much engine coolant is allowed to influence the water temp in the hot water tank. If you are running an EGR Detroit (hotter running), only open it half a turn. Opening it wider = early and often failure.

This is the simpler/cheaper way to do what Jon is doing (but less elegant).

[Bernard]

The only thing a partial valve opening does is slows down how fast engine coolant raises the water temp. If the valve limits the coolant flow sufficiently the water in the tank may ever get hot, which a lot of owners choose to do rather than deal with scalding temps or pressure temperature valve issues.

If you are very, very patient or extremely lucky you vary the valve opening to allow the precise coolant flow that will bring the water temp to an acceptable level, but not enough to overcome the heat loss so the water temp is limited. Of course that depends on the bay temperature, how long the coach is being driven, how much hot water is being drawn, all of which vary.

[Archived]

Jon,

What do you use for controlling the valve? An aquatstat or the line voltage off of the water hearters limit switch?

[Fred F.]

I added a solenoid valve in the coolant line to the water heater and control it via a second thermostat, My manual valves are wide open.

My second thermostat has a set point the same as the thermostat that controls the electric heater so our hot water temp is the same whether we are driving or parked using a power pole.

[Dennis & Jackie]

Thanks

[Dan]

I just want to swap out the valve with a replacement, not add more complexity to my coach that requires tablet computers, retinal scan security and a Flux capacitor to determine when to open a pressure release valve 🙂

[Doug]

Charles,

Before you change out the valve, accept the advice provided in an earlier response to check the accumulator tank and make sure it has the correct bladder pressure. If your accumulator has lost pressure or is water logged you might as well buy the pressure relief valves in quantity.

Having said that, if you do not wish to add some means of limiting tank temp, either by turning off the coolant valves to the tank, or installing a thermostatically operated solenoid valve, you are still going to dump hot water on occasion through the relief valve because the tank water temps are going to open it.

[al]

Jon, I realize this is an older thread, but I was wondering just exactly what you used as a temperature control valve. Was is a Dwyer 38R ? I too have had a hot water blow-off a few times due to 200 degrees plus series 60 engine temps and would like to install a temperature regulating system for this issue. Another issue or problem is the high coolant temperature can trip the electric system safety breaker causing the wife to shout out from the shower the next morning “There is no hot water!”.

[Roscoeapproved]

Jim. I used the internet and without digging through the log book in the bus the modifications I made to regulate water temp when the engine coolant is the heat source was two simple searches. The first was a continuous duty 24V DC solenoid valve suitable for water with pipe fitting threads of 1/2″. The solenoid valve is normally closed.

Then to supply or interrupt power to the solenoid valve I used a bi-metal thermostat (commonly known as a thermodisc) normally closed, but opens at 125 degrees F. I brought power to the disc which was mounted in contact with the tank near the factory tank thermostat from a key-on power source from the rear electric box. I put the solenoid valve in the coolant line feeding the HW tank. I ran the ground wire back to a terminal in the rear electric box.

Now hot water, regardless of if it is heated via engine coolant or the electric heater is limited to 125 degrees F. Before the addition of the coolant control the HW was absolutely scalding when heated via coolant, and often the temperature pressure valve on the tank would release water. Not any more.

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Jeff and Lindsay

91 Marathon XL