Simpson 4400psi 4gal chatters when on tank

I see so many of you that built a rig useing a tank for your PW backup water supply. My PW chatters and cries for water… Why??? I just built a rig for my soft wash 7.5gal pump using a 55gal white plastic drum laid on it side. I have a 3/4 water inlet with a Hudson valve. Estimated captured water to use is about 45 gals. The outlet is 2in reduced to 1in pipe for supply. It works great when reduced from 1in to a 3/4-1/2 barb into the banjo mixer and out to a 3/4 hose to the 100ft flexzilla hose to softwash. Big problems when I supply water to the PW. I use a 1in pvc line to the pump an connect with a 3/4 braided hose . There is about 8Ft of 1in pvc with 1 90degree and about 2ft of 3/4 braided to connect. When the PW is running, it’s almost cavatating and low on pressure even with a full tank… pumps like an animal when on a hose line… what’s so special on your rigs that keep this from happening??

Is your machine belt drive, direct drive, or gear drive? And why would you lay the drum on the side?

Are you running both pumps at same time?

Direct drive. Laid on side to prevent toppling.

Could. No problems with tank going low. Changed to 3/4 braid on PW water intake to check for any air draw. Saw none. Could it be water psi from tank?

Direct drives don’t work well off a buffer tank. They need some head pressure like from hooking up directly to a customers garden hose.

Thought so… well at least I have a great softwash and scrubber combo… maybe when I grow a little, I’ll go belt and a bigger rig. Still works for a one man band. LOL Thanks for confirming my thoughts.

Definitely more aerodynamic with tank on side but probably time to upgrade the pump, ah just saw last picture. I understand it on wheels but it’s not a mobile home all that pvc gotta go, especially hat 45

Direct drives don’t pull water. But you can make it pull a draft. Sometimes. Try holding the gun open,lower the throttle to idle. When you get water at the tip slam the throttle all the way open. Also those pumps are famous for destroying check valves. It may be replacement time


I had the same issue when I first started and bought a 110v water pump. It worked well enough but finding an outlet was problematic at times.

Could get one of the gas pumps from Harbor Freight…we use one on our water trailer to transfer the water into the truck’s buffer tank.

Thanks guys, all of that sounds good but the PW has less than 50 hours on it. I did run it with the hose hooked up direct and it runs great. I think I’ll just use the tank as it sits for soft wash for now instead of a buffer. Have had no line in water restrictions yet.

1 Like

Raise the buffer tank above the inlet on the high pressure tank. That should resolve your problem. I have a direct drive that the buffer tank is sitting above the inlet to to PW and have no problems with it.

That’s a great idea… water pressure builds while running downstream. Now to figure just how to move the buffer up about 8in. Or I could drop the rig hitch to the ground. …but I’d need a jack to rehook. LOL or I could get one of those 225gals… fill it it up 1/2 and let the tank water weight downpressure do the work. That’s a lot of customer water waste… I can’t see a real solution right now but to run a few 45s to replace the only 90 and use the PW connection for a hand wash/ tank drain outlet… looking foward… for my size of biz… the only reasons I can really see for a buffer is for softwash and a pressure pump bypass return to help keep it cooler… I’ll just need to grow a little and apply the profit to upgrade… thanks for the great suggestions…

How about just hooking your customers water supply direct? A 4 gpm unit will be fine 99% of the time with standard homes water supply.

1 Like

I second @Nickski with just trying to use the customer’s spigot as your supply. You’d lose being able to let off the trigger for prolonged periods of time but you’d save your pump from air cavitation.

If set on using the buffer, also consider lowering the washer - 4 bolts and it’ll come off the frame.

He could also just plumb it to shoot bypass water on the ground when not on the trigger.

That’s what I was doing before this project and what I’m doing now with no problems…

Did you ever get it figured out on using a buffer tank without problems?
I have a few jobs lined up that I don’t have access to their water…
4gpm direct drive, I was thinking about using my softwash motor 7gpm to feed the pressure washer lol