Stuck in a pickle

As some of you may know, i’m running some low tier 4/4400 machine as i‘m still getting my foot in the door of the business. It’s a simpson 4400/4gpm turd box. Yesterday on a house wash my pump practically blew up, its got a hole on the bottom that leaked all the oil out. I’m looking to get a new 4gpm since it’s all my 13hp motor can push out. I know the best pumps for 8gpm are udor pumps, maybe general too. But for these weaker 4gpm pumps my options seem to be AR/GP. Is there any brand in particular that reins supreme for these lower flow pumps? I’ve been suggested by a few people to buy this AR pump i’ll link below

Here’s the link im about to pull the trigger on so i can get back to work asap

I’ve heard bad things about built in unloaders off my memory idk if this is classified as a built in. Is this a waste of money? Can i plumb a buffer tank to it or do i need a belt drive? or is belt drive only needed if you’re running exclusively off the buffer/reservoir supply?

The GPMxPSI/1100 says 4gpm is the highest i can go with a decent amount of pressure for flatwork. But i do see some people going over that limit. Would a 5/3500 be possible with 13hp or should i just stick to 4/4000? 4k is way more than i’ll ever need but it seems to be the only option for the pumps i’m seeing at 4gpm

I run a 5.5GPM 3800PSI Allison pump with gearbox from Envirospec on my GX390. I have it set to 2500PSI which is what the GX390 can provide with 5.5GPM. $579 price. Includes the gearbox, takes 4 bolts to attach which it comes with.

Link to Pump with Gearbox


@TexasPressureWashing I was just trying to find that page on Envirospec.

Do they give veteran discounts? I saw something on there about it.

I forgot to ask actually.

When my built in unloader gave, I got this unit here. Easy install and power horse. With good flow I swear it was closer to 5 gpm.

You have the ability to bypass the water to a tank with this unit as well. Just have to reconfigure the hose.


You could just get the pump as well if you have another unloader in mind . That link includes the unloader

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I would definitely spend the extra $400 (including a ZK1) to not have an unloader attached to the pump. But that is thrifty.

So you reckon I can get that with my current 420cc 13hp engine, maybe get 2800-3000 psi out of it? Most of my work is flatwork like driveways patios etc so the extra psi does help. It’s out of my budget right now since I just had to pay for insurance and school the other day, although I was in the middle of a $385 job that once completed could let me buy that pump. I might have to rent a 4gpm from home depot and finish the house wash with my X-jet. Shouldn’t be a problem i believe

I can’t say for sure but I could see an actual 420cc pushing it to 2800-3000 PSI. The GX390 is actually 11.7HP which Honda finally admitted.

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The pump you linked says 6.3 gpm. is that correct? I’m gonna go ahead and rent a washer to finish this job so i can purchase the better pump you linked. Im skeptical if my motor is even 420cc… got the whole thing with 4gpm pump for $800 which sounds too cheap considering the gx390 alone is around that if not more.

That’s what I linked

It will get you by so you can save for a real set up


Predator makes 420cc motors. The website has a text error. The previous page shows 5.6GPM when you click it lists the bigger one. You can call and order as well.

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You must be bypassing quite a bit of water when you’re on the trigger no?

@mikesPWclean where are you located? If your close to Charleston SC I’ll loan you one of my backup units.

For which the 5.5? No I don’t seem to be.

When you set the unloader were you able to see how much was bypassing or was it going in to the tank?

Curious why this is in the lounge?

i’m in north texas, i appreciate the offer though!

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Lol yeah for the price of gas you could just buy a new one, thought I’d offer though.
I never mind helping someone if I can!


It was a small amount when on the trigger. Most of the flow for both went to the gun.

It’s just supposed to trickle when on the trigger. I bet you can get a bit more than 2500