Pressure drop at gun- CAT 310 pump

[Husker37]

Hi all- I've learned a great deal from many on this forum from reading posts over the years, but have never actually posted. I have a problem that I can't seem to solve and I'm hoping that you can help me figure out what I'm missing.

I have a bay that lost pressure slowly over time, and when I finally got around to dealing with it, I found some issues, but still have a problem I can't solve. The bay was pulsating and had very low pressure. I found an air leak on a push to connect fitting that feeds the pump which took care of the pulsating. I know the pump is pretty old and worn and the head is washing out, so I swapped the head with a rebuilt head with new high and low pressure seals and that fixed my overall pressure problem.

Now I have plenty of pressure and no pulsating, but when the gun trigger is depressed the pump pressure drops by about 50% (if I have it regulated to 1500psi, it drops to 700, regulated to 1800 drops to 900, etc.) and it is apparent in the bay that there is a pressure drop.

Things I have tried:
-Swapped gun with a different bay that is working- No change
-Replaced gun/tip to new - No change
-Replaced the regulator/unloader on the pump- No change
-Replaced the check valve at the bay that prevents pressure from bleeding back to low function lines- No change
-Checked water flow to pump and compared to other bays- Gravity fed from overhead- Water flow seems just like other bays
-Swapped out all 6 valves in the pump head to new- No change
-Shut off the ball valve to my weep system to take check valve out of the equation- No change
-Tightened all hose clamps on supply line to ensure no air leaks- No change
-Checked to make sure that my spot free check valve isn't leaking on that bay- Check valve good

I'm at a loss of where to go next. I'm running a CAT 310 pump on a D&S mini stack setup. I've attached a picture of my pump setup to show all connections and regulator setup.

I've had many similar problems over the years and have been able to figure them out. I am wondering if I'm overlooking something simple here?

Any help would be greatly appreciated.

Thanks!

Tom

 

[MEP001]

You could have a bad regulator even though it's new. Normally I would test it by pinching off the bypass hose but the way it's plumbed there isn't one.

There may be a weep check valve on the other side - if that's bad, your pressure could be lost through it.

 

[Husker37]

The pump outlet goes into the regulator, through the regulator, and to the bay. Regulator was replaced with a like for like with the same fluid path. The regulator is there, just hard to see in the picture as it sits behind the blue hose.

 

[MEP001]

The pump outlet goes into the regulator, through the regulator, and to the bay. Regulator was replaced with a like for like with the same fluid path. The regulator is there, just hard to see in the picture as it sits behind the blue hose.

Sorry, you replied to a post I edited. I didn't see the regulator at first.

 

[Husker37]

Thanks MEP. I can try swapping the regulator again.

I do have a weep check valve, but I have installed ball valves inline so I can anti-freeze and shut down certain bays in the winter, so I've got it valved out of the system right now.

I appreciate the ideas!

 

[mgmtoo]

You could also have a bad hose, partially collapsed internally.

 

[Randy]

He's got a pump head problem. Been there and done that

 

[Husker37]

Yep, Randy strikes yet again and calls the problem. He had me swap heads on two of my pumps and the problem followed the head. Haven't had a chance to dig into the head yet to see exactly what is wrong, but Randy got me down the right path.

Thanks everyone. Much appreciated!

 

[cantbreak80]

He's got a pump head problem. Been there and done that

I was gonna say that.