Pressure Relief Valve - Power Wash Network "The Power Wash Contractors Forum"

the_GUNN_man · #1 (**permalink**) 03-12-03

I had my pressure relief valve open up on me today. Every time I turn on my machine it sprays out of the hole on the side of it. I get low pressure out of the wand. When I turn the machine off I notice that it still drips out of the hole in the relief valve. That makes me think the relief valve isn't resetting. I figure that when the machine is turned off the pressure drops and the valve should seal back up, but what happens is you can see it still drip from the hole meaning that the valve is still open even when the machine is off. How do I tell if my pump is bad, it is an unloader problem, or it is a bad relief valve? I did notice earlier today I was getting some leaking form the pumphead. I thought earlier today that my pressure wasn't what it should have been. By the way I wasn't running any hot water today. Any help or thoughts would be appreciated. Gwas is coming over tomorrow to try and help me figure it out. He is a really great guy. I would never have thought that a fellow pw'er so close to my area would be this helpful.

Larry L. · #2 (**permalink**) 03-12-03

Take a wrench and tap it,it may unstick it

Mark · #3 (**permalink**) 03-12-03

Steve,

it sounds like it is time to either disassemble and clean your pressure relief valve or replace it.

The relief valve / pop off valve leaking would cause a drop in pressure at the nozzle, however a leak at the pump head also would create low psi at nozzle.

If the water is leaking from underneath the head it is probably worn packing.

I am available to help troubleshoot by phone feel free to call me.

B.E YOUNG Sr, · #4 (**permalink**) 03-13-03

GUNN MAN,
A thermal releif valve functions like a thermostat. It will open if the water temp. in the pump gets above 140 F or temp. specified by valve. It should close once the temp. drops back down.

Some of the valves can be disassembled and cleaned like Mark said. The valve should not open up on start up unless it is defective or you have low flow to the pump.

Check to make sure you have good flow to the pump. No collapsed, pinched hoses, stuck float valve or inadequate water source.

Ater checking the above you can try this:
A quick test of the pressure releif valve would be to remove it and install plug. If the valve was defective you should be back to normal pressure at the gun!

Replace the valve asap if it can't be cleaned. If you purchase a new ($10.00-15.00) one try and get a Hypro valve or one that can be disassembled and cleaned. You can also test a valve after cleaning by placing it in hot water. Place on the stove in a pot
of water. Cut heat on and bring temp. up to valve spec. using a thermometer. The valve should open. Cool down it should close.

Beleive it or not the pump is the most durable part of any system. Low pressure is usually the fault of an external component.

Hope this gives you some insight!

Mark · #5 (**permalink**) 03-13-03

B.E.

Great description of the function of a pump thermal valve.
I believe you were referring to a pump thermal valve.
aka: pump saver, pump guard etc.

I was referring to the pop of valve or high pressure safety relief valve, which is set at a pre-determined pressure and when the pressure exceeds that setting the pop off valve opens preventing damage to the system.

Both valves provide pump protection, the thermal valve protects from excessive heat build up in bypass, and the pressure relief valve provides protection from damage caused by over pressurization.

Austin · #6 (**permalink**) 03-13-03

I had one of them boogers break on me due to the winter weather. Like 6 or 8 bucks for a new one.

I thought earlier you might have been refering to the rupture disc.

Mark · #7 (**permalink**) 03-13-03

GP COMPACT 1/2 MPT 145F THERMAL RELIEF

General Pump Thermal Relief Valve:

Protects the pump from damaging heat build up while it is in bypass mode. The thermal relief valve, sensing a rise in temperature opens and discharges a small amount of heated fluid. This allows cooler water to enter the system and cool the pump. When the gun is discharged the cooler water will cause the valve to close immediately.

FEATURES:

* Most consistent temperature range on the market
* Quickest response to rising temperature
* Less stress on the pump
* Shorter overall length
* Most cost effective thermal protector on the market
* Mounts easily in the pump manifold, inlet water supply or bypass loop plumbing.

Mark · #8 (**permalink**) 03-13-03

The pressure relief valve is a safety device on the pressure washer. When a pre-determined pressure is reached within the system, the valve opens and releases water into the atmoshpere, or back into the line. The pressure relief valve is normally a second line of safety defense when used in conjunction with an unloader. It can also be used as the sole pressure safety device when installed in an open gun system.

There are other styles of pop off and thermal valves the 2 I posted are for illustration purposes.

Giant pumps used to frequently use "rupture discs" instead of resetable valves.

oguard · #9 (**permalink**) 03-13-03

Pressure relief valves like the RV500B from General are usually factory set and prevent an over pressure situation. Once they pop, although ostensibly automatically resettable, the spring inside is neither large enough nor strong enough to remain at the original setting. The same applies to a thermal relief valve. The former is a pressure sesitive relief spring the latter a temperature sensitive relief spring. The RV500B should cost $20-30.

BUT, you need to determine what caused the over pressure in the first place. Plugged coil? Worn unloader? Grit in the gun/tip? nce you know that then you can replace the pressure relief valve. To set properly run the machine to full pressure and open the valve until it releases, once the valve pops turn it back 1 1/2 turns and lock it in.

Hope this helps? Cheers.

B.E YOUNG Sr, · #10 (**permalink**) 03-13-03

Mark,
Yes I was refering to the thermal releif valve. Sorry about that!

Would it help to install two TRV's on a tee. Thinking would be you would flood the pump with cool water faster in a heat up situation?