PSI the same when gun trigger pulled or not

[MEP001]

An unloader relieves the pressure from the system when the trigger is let go and is best used with positive shutoff guns.

It only works that way with a shut-off gun.

Using an unloader or pressure regulator can be used on electric motor or engine powered systems.

You basically just said that none of it makes any difference.

 

[Stuart]

It only works that way with a shut-off gun.


You basically just said that none of it makes any difference.

...............trigger is let go and is best used with positive shutoff guns.
Yep, an unloader is best used with shutoff guns. A weep gun can be used but the unloader will pulse the pressure- but can be used.

And I am not sure where where you are reading that I stated it makes no difference. Motor or engine driven pumps can use either the unloader system or pressure regulator system. The difference is in the operation of the unloader system vs the pressure regulator system.

 

[MEP001]

An unloader will work the same as a bypass regulator with a weep gun because the weep is enough to keep it from trying to unload the pressure from the system. A small leak will cause an unloader to pulse trying to maintain the downstream pressure.

 

[Stuart]

An unloader will work the same as a bypass regulator with a weep gun because the weep is enough to keep it from trying to unload the pressure from the system. A small leak will cause an unloader to pulse trying to maintain the downstream pressure.

well I guess all six of my pumps with unloaders and weep guns did not get that memo.

 

[MEP001]

well I guess all six of my pumps with unloaders and weep guns did not get that memo.

So when the trigger is not pulled, the pressure on the gauge is continuously dropping to zero and coming back up to pressure?

 

[Stuart]

So when the trigger is not pulled, the pressure on the gauge is continuously dropping to zero and coming back up to pressure?

You got it! when I got into the carwash business 32 years ago, that was the setup I walked into. Giant unloaders with weep guns and the pressure gauges looked like kids on pogo sticks.

 

[2Biz]

Hmmm...That's interesting. I use the Giant 1400 PSI Unloader with weep guns:
https://www.kleen-ritecorp.com/p-1961-giant-adjustable-unloader-1400-psi-13-gpm-yellow-springs.aspx

I have the pressure set at 1200psi (Trigger pulled) and when the trigger is released, pressure goes up to about 1250 psi and holds that pressure steady. No pulsating...When the unloader starts to wear, the pressure will spike a little higher when the trigger is released. But still no pulsating on and off. The pressure stays constant. I had some unloaders in service that looked like they were 20 years old! The paint had wore off the springs before they failed....

 

[I.B. Washincars]

I have that same Giant on some of my Mark VII equipment as well. Correct me if I am wrong, but I think a check valve in the outlet of the unloader has been removed, which makes it a regulator. I was told something to that effect a long time ago from James at Arimitsu, but I may have it mixed up somewhat.

 

[MEP001]

The check valve is there so the pressure can stay trapped in the hose when a non-weep gun is used. I've seen the check valve break and stop flow to the bay and had to remove the poppet, but as a rule people that use unloaders with a weep gun don't remove it.