Buffer Tank?

I am sure this has been asked but I am not able to find the answer to my question. I have a 4200 psi 4 gpm pump. When I hook a normal garden hose up to the pump with the motor off, water with shoots out of the high-pressure side where the pressure wash hose hooks in. when I did a test tho it took a minute and forty seconds to fill up a five-gallon bucket with the garden which I think means the pump isnt getting 4 GPM. SOOO with that being the case I have set up a vertical 65-gallon water tank which as a buffer tank. When I hook it into the pump with the motor off nothing shoots out of the high-pressure side like with the garden hose. I did a test with the biuffer tank and it fills up a five galllon bucket in just over a minute. So is the water not shooting out of the high pressure side with the motor off a problem. Sorry if this is confusing.

I forgot to mention that the water only comes out of the high pressure side when the high pressure hose is not connected.

Belt driven?

No. Direct drive which I understand does not pull water like a belt driven would. But I have read a lot of post where people are using buffer tanks on Direct Drive machines which seems like my only option since the water hose is only putting out about three gallons a minute.

Get rid of machine and get a belt driven. Problem solved.


Technically a direct drive won’t pull water from your tank. However lots of people use a buffer tank with a direct drive. Try and get you tank outlet above your machine’s inlet and if you park on a hill make sure that the is still lower than the buffer.
Hopefully someone with experience will chime in.

@Aschultz89 Other option is to buy a 12v 5.5 gpm pump, a marine grade battery, water tight battery box, plumb in a draw tube to the 12v pump because it can’t be gravity fed, then you can run a buffer tank, but you’ll blow through a 65 gallon tank pretty fast. Refilling the 65 gallon tank from a hose that’s barely pushing 3 gpm you’re going to have to take a lot of breaks though…

And after all that trouble, the money and time you’ve spent would probably be more than the difference between the cost of your machine and a belt driven machine.

But yes. If your tank is above your inlet, your hose out of your tank is 2" reduced to 1" right up next to your machine’s inlet, the tank is vented properly. The higher the tank above the machine the better. There are a number of people on this forum who run tanks that way.

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Consider checking Craigslist for a belt driven. I see good machines for sale all the time for around $600ish. I just bought a belt driven 4/4 with 13 hours on it from a painter for $650. Couldn’t be happier with it

@Aschultz89 here’s my set up. Sometimes I have to take my machine off the trailer when water pressure is low and I wanna use the 5gpm machine. Actually I rarely carry the 4 gpm machine anymore.

I’m doing a lot with a little here in KC, but everyday I wish I would’ve been able to get a belt driven machine locally. Was in a time crunch on a huge job. Anyway. I won’t own a direct drive machine ever again because it’s such a pain to have to worry about water pressure or getting the machine down blah blah. This set up gives me 10 gpm and I can send video if you’d like to see it.

You can find IBC totes on Craigslist. I got mine for like $60.

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Really appreciate you taking the time to upload the photos. They are definitely helpful. Still working on my trailer set up
And figure things out.

I posted about this a while ago. I think the title was “help! flow problem?”.

I’ve got the same set up except my PW is belt drive. My buffer tank is also 100 gal so a little bigger.
I was not getting enough flow from my tank either. So I plumbed in a 1in suction hose to the tank. (i had 5/8 before) and that fixed my flow problem. Then the problem is there isn’t enough pressure from the tank to prime the pump. So I hooked up a regular garden hose to the pump to prime it, then unhooked it and connected my buffer tank hose and made sure there were no air bubbles in the line. Once I did all those things it started working great.

I am no expert, I am just starting out as well. It’s my understanding that you can’t suck water from a buffer tank with a direct drive pump, I don’t know how it works I just know they say you can’t.

I can take some detailed pictures tomorrow of my now working set-up and post them here if you like.

Does yours have easy start? Or a 1/4 inch hose that runs from the inlet to the unloader? If so you can run that hose back to the buffer tank and it will assist in priming it.

Got some detailed pictures here of my setup.

Here is my 130 gal tank.

I have a Hudson Float Valve set up to fill the tank to 100 gal

2in PVC running from tank. I have two ball valves plumbed in. One to turn off water to the pump, the other so I can empty the tank.

From the PVC to the tank I go to a 1in suction hose. So I have plenty of flow and the hose won’t collapse.
Here is the link for that

My water level is about 5 inches above the pump inlet. When testing the tank at that level I got about 5 gal a minute.

Then I have a unloader valve that feeds back into the tank

It’s not the best setup, but it will get me by till I upgrade. I hope this helps you

In my opinion your feed line is too small coming out of the tank and has too many 90 elbows in it. In addition to that the buffer tank is squatty so you could benefit from putting the tank on a riser to help use gravity to increase the flow rate.

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Didn’t you put up a video recently?

I have 2 inch line to 1 1/2 in line to 1 inch all the way to the inlet. 1 - 90 degree turn, but it’s 2 inches and sloped downhill. I get nearly 10 gpm out of my buffer tank, but only if it’s 50 gallons full or more. Should’ve raised it, but I already have the tank U-bolted on, pvc glue up for the outlet and inlet. No time this season to change it, next year is a new set up. Oh well.

No need to raise tank. My machines sit 3 feet above my water outlet. You are getting air in the line. Probably from draining the tank thru same line that feeds machine. If all the water is drained it will take a minute to purge the line of air. Replumb or put a check valve. Quit draining the tank would be easiest. Get rid of the pressure gauges also. Friction loss and air leaks need to be minimized