Plumbing pressure relief

I have to agree that the problem is the toilet, not the WH or the pressure, or a lack of an accumulator tank. I've been RVing for more than 30 years, owned 3 different RV's (and grew up camping in several more prior to buying my own). I also camp regularly with at least 3-5 others. None of them used an accumulator tank, and in EVERY case of a water leak, it was a "LEAK", not a pressure or air pocket or WH problem. An accumulator tank is a nice add-on to smooth flow, add some small water use without the pump waking your wife up when using the toilet at night, etc., but a leak is a LEAK, and leaks should be fixed. We all know of the major damage that a water leak can do to our rigs. Covering one up with an accumulator tank is a bandaid that doesn't address the actual problem, and is a temporary fix at best; one that can and likely will lead to damage down the road.

Razorback wrote:
May want to check the water heater thermostat. If the low temperature thermostat (or both low and high) is stuck the water may be heating higher than it should causing excessive pressure.

If 'normal' temp t-stat fails then High Temp t-stat trips shutting down DC

Both failing......highly doubtful

But toilet valve is STILL leaking thru overfilling toilet

May want to check the water heater thermostat. If the low temperature thermostat (or both low and high) is stuck the water may be heating higher than it should causing excessive pressure.

Toilet valve has already failed....it is fill the toilet bowl and overflowing

Replace the toilet valve, add an accumulator and re-establish air pocket in WH Tank....done!

time2roll wrote:
80 psi is the max pressure according to plumbing code. More like 50 to 65 psi is normal. The T&P valve at 125psi is there to prevent tank rupture not to regulate pressure to code. The air bubble in the water heater is not reliable and one more maintenance headache. The accumulator can take the place of the tank air bubble on a permanent basis.

Yes the valve or a fitting could be weak. The spike in pressure can still exist and exasperate the issue.

Not sure why such resistance to the accumulator as a permanent solution.

So who uses 100+ psi to blow out the water when winterizing?

Accumulator in this case most likely is not the real "fix" which is why the "resistance".

Accumulator is not REQUIRED to a RV water system to work properly, period.

Adding a accumulator in this case just basically shovels the real problem under the carpet..

The real problem in this case is most likely a FAULTY TOILET VALVE OR CONNECTION TO THE TOILET VALVE..

I KNOW THIS FROM EXPERIENCE..

I mentioned before that myself, I replaced a old toilet with a brand new one and the brand new one while it was fine with my house pressure of 50 PSI, it WAS NOT FINE WITH CAMPGROUND PRESSURE ABOVE 50 PSI.

The water valve in the new toilet was DEFECTIVE, the valve when manufactured is made in two separate parts, internal parts are put in and the two halves are then sonically welded together..

Sonic welding depends on having two pieces in good alignment.. Mine looked like the two halves were slightly misaligned when welded.. That misalignment created a weak spot/ microscopic pin hole in the weld that would seep when the pressure was above my home water well. It NEVER LEAKED AT HOME but yet leaked at the campground.

Drove me nuts to the point I turned off the water to the toilet until I needed to flush it.

This IS the reason I mention that the OP NEEDS TO LOOK AT AND WATCH THE CONNECTION AND TOILET VALVE.

Fix the problem, not mask and hide the problem.. Adding a accumulator is MASKING the problem and a dangerous game you are playing since a defective/bad toilet valve or even plumbing connection could fail down the road.. I would rather IDENTIFY the problem and REPLACE the valve and or plumbing connection now before the OP floods their RV.

Keep in mind that the issue happens after TEN minutes after they purge the pressure. TEN MINUTES. That is a pretty fast ramp up of pressure, water heater would have to be near boiling to pressure up the water that fast and an accumulator is eventually going to go past that tipping point of leaking again.. Eventually Accumulator WILL run out of "cushion" and the pressure overall will still climb (you can only pressure up an accumulator so far and then the cushion of air will not compress much more if any).

Accumulator will not prevent a failing valve from failing it only will DELAY the failure of the leak.. It is not a "fix all"..

I don't know why the resistance to verifying the leaking spot on the toilet and possibly replacing the toilet valve and/or possibly replacing the plumbing connection to the toilet.

time to roll, If you are asking me you are asking the wrong person ;)

I have had an accumulator in my system and a pressure regulator set at 45-50 for years. :h

80 psi is the max pressure according to plumbing code. More like 50 to 65 psi is normal. The T&P valve at 125psi is there to prevent tank rupture not to regulate pressure to code. The air bubble in the water heater is not reliable and one more maintenance headache. The accumulator can take the place of the tank air bubble on a permanent basis.

Yes the valve or a fitting could be weak. The spike in pressure can still exist and exasperate the issue.

Not sure why such resistance to the accumulator as a permanent solution.

So who uses 100+ psi to blow out the water when winterizing?

Old-Biscuit wrote:
T&P on RV water heater will weep at 125 psi


Not many RV MFGs install a check valve on INLET
And not many have issues with T&P weeping but it does occur
Some can experience weeping EVEN with an air pocket....that is where an accumulator tank can help
** most install accumulator tanks to help with pump cycling during low demand & being able to turn pump off at night and still be able to flush the toilet
But they will also help control system pressures

My WH Tank does NOT have ANY check valves..has 3 shutoff valves
And even w/o check valves I have never had T&P weep except when air pocket was lost.

I think the thread has drifted a long ways from the OP..

To refresh, I am quoting the OP that started this thread...

I am Yu wrote:
I'm running on internal water (not city water). I don't leave the water heater turned on all the time (too wasteful to do so) and when I turn it on it raises the pressure in the whole plumbing system way too high, and I get water leaking from the toilet onto the bathroom floor. The only way I've found to deal with this is to shut off the pump and briefly open a faucet every 10 minutes to relieve the pressure, until the heater gets hot and the pressure stabilizes, which gets pretty annoying.

There is a pressure relief valve on the water heater, but apparently it's only intended to protect the heater tank, and opens at too high a pressure to do anything for the plastic plumbing.

Is there some kind of relief valve that opens at a lower pressure, which I could install somewhere in the system and have it drain overboard?

So, the real issue the OP has is the TOILET LEAKS, but ONLY WHEN THE WATER HEATER IS RUNNING.

To "fix" OP turns off the water, bleeds down the pressure on the water heater then restarts everything.

So, the REAL issue is the TOILET leaks when there is MORE PRESSURE.

Bleeding pressure off the system stops the leakage.

Issue IS NOT the water heater, nor is it lost air space nor is it not having a bladder tank..

The issue is most likely the TOILET FILL VALVE IS FAULTY and it shows up ONLY when there is more pressure.. I HAVE BEEN THERE DONE THAT.. Relieving pressure is just hiding the symptom temporarily.

Op needs to gain access to the back of toilet where that water line connects to the fill valve and observe EXACTLY where the water is coming from.

T&P on RV water heater will weep at 125 psi


Not many RV MFGs install a check valve on INLET
And not many have issues with T&P weeping but it does occur
Some can experience weeping EVEN with an air pocket....that is where an accumulator tank can help
** most install accumulator tanks to help with pump cycling during low demand & being able to turn pump off at night and still be able to flush the toilet
But they will also help control system pressures

My WH Tank does NOT have ANY check valves..has 3 shutoff valves
And even w/o check valves I have never had T&P weep except when air pocket was lost.

Lynnmor wrote:

Gdetrailer wrote:

Lynnmor wrote:

mobeewan wrote:
Accumulator tanks are now required at the hot water outlet pipe of water heaters on residential construction and when replacing WHs in existing homes.

I believe that is local codes, it wouldn't make sense for those on a well with an open system that has no check valve after the tank.

A "properly" installed water well WILL have a check valve at the pump.

Never want water to flow back into your well.

My well driller put a check valve above the submersible pump down the well.. I have an additional check valve between the pressure tank and well head for good measure.

Correct, the check valve(s) is on the PUMP side of the tank, not on the HOUSE side. The tank has the air pocket to keep pressures from going too high. What I said before is correct.

I was giving a bit more complete explanation on a HOME well system which lead into the fact that the OPs TOILET VALVE actually may be at fault similar to what I ran into.

Something else also, unless the water heater is heating the water to high enough temps to create steam I highly doubt that it will cause enough pressure without an air pocket to cause the toilet to start leaking unless there is a FAULT at the toilet..

The T&P valve IS there to relieve WATER PRESSURE in the event of over water heater overheating..

From HERE

In a standard water heater, the water is heated by a gas burner or electric elements. As the water reaches temperatures between 120 and 140 degrees Fahrenheit, both the water and the water heater's metal tank expand. Some expansion is normal, but too much expansion is unsafe. When the temperature reaches 210 degrees or the pressure reaches 150 psi (pounds per square inch), a properly functioning T & P valve opens and expels hot water and steam through the discharge tube.

One would really need to put a pressure gauge on the system and monitor the pressure to see what is really happening rather than making a bunch of guesses..

OP could even have a faulty pressure switch on the water pump but in reality the toilet should not leak even with CITY water pressures up to 100 PSI or better (yes, city water CAN get there).

Under NORMAL conditions with RV water heaters I have seen T&P valves "weep" some even with a newly filled water heater tank. And that may be partly due to a small air pocket but also have to consider RV water heaters operate at a much higher temp, of 135F to even 140F..

As far as the check valve goes on the inlet of the water heater, it should have had one from factory, even my 1980s TT HAS ONE.. Of course, with the factory check valves they use the cheapest ones they can get their hands on which are typically the plastic body with inline spring and plunger and the plunger has a rubber gasket that fails.. I changed mine to a all brass swing check valve for more reliability and much quieter operation (that plastic valve would "sing" when water was moving and DW didn't like the noise).

And yes, I would agree that some expansion tank may be nice to have as it will buffer the water pump but it is most likely not the fix or issue here.. I suspect the issue IS the OPs toilet water valve..