My pressure relief valve on my hot water tank is 150 psi. The domestic water pump is max 40 psi. I am considering replacing it with a 40 or 50 psi relief valve as the 150 psi will never be reached as it will blow every hose onboard. Before I change it I would appreciate the considerable experience and expertise of collective forum. So over to you. Thanks.
Hot water relief valve
- Thread starter east coaster
- Start date
The pressure relief valve needs to be high enough to avoid nuisance blows. Setting it too low, at 40 or 50 psi will cause it to blow every time the HW tank gets hot.
When water heats up, the pressure increases, the pressure relief valve is there to dump the pressure before the tank blows up. Trident potable water hose has a burst strength of 250 psi which is well below the 150 psi of the T&P valve.
So, there is no need to replace the valve. At least once a year excercise the valve by lifting the lever a couple of times to make sure it releases.
When water heats up, the pressure increases, the pressure relief valve is there to dump the pressure before the tank blows up. Trident potable water hose has a burst strength of 250 psi which is well below the 150 psi of the T&P valve.
So, there is no need to replace the valve. At least once a year excercise the valve by lifting the lever a couple of times to make sure it releases.
An additional item to Dave's dissertation above is to install an expansion tank. This will avoid overpressuring the system each time you start your engine with a cold hot water tank. This usually causes your relief valve to weep on startup.
I think this comment is backwards. The burst strength of the potable water hose mentioned is 250psi and is well ABOVE the 150 psi of the pressure relief valve dump point.
Oh yes, very true, very true indeed but we try not to mention these minor little things in polite sailing society.
But Jeez, talk about getting it backwards. Holy Crap, I think Dave was smoking the drapes when he said :
Everyone and his pet dog knows that when water heats up, it's the volume that increases. But if that original volume is constrained, then and only then does the pressure increase.
BTW, don't mention this to Dave. I hear he upsets easily.
First you accuse me of writing a dissertation, then you tell me the explanation isn't long enough. Will you make up your mind.
Gentlemen, thank you for your colourful and interesting responses as well as your repartee with respect to one another. I will therefore leave the system as it is and contemplate where a possible expansion tank will be placed physically. Again thanks to you both and others who had read this thread and gave it some thought.
Tips on CHECK VALVES:
1) Flapper type or Ball type [in line orientation important]
2) Double Clamp connections.
3) Function tested each season.
______
The Water Heater "Relief Valve" is a Check Valve
________
Visual of a Big FLAPPER type.
______
In the chemical industry we had a saying.
Like Murphy's 1st Law.....
Check Valves DON'T
Jim...
While the relief valve is a check valve, it is not in the proper place for that function, and cannot serve that function.The Water Heater "Relief Valve" is a Check Valve
In the chemical industry we had a saying.
Like Murphy's 1st Law.....
Check Valves DON'T
Jim...
The worst that can happen with a check valve on the cold water inlet is that the cold water circuit gets hot water flowing back into it. Which would be the case if there wasn't a check valve. Pretty much all water heater manufacturers prescribe a check valve on the cold water inlet.
Mark