8 gpm with GX 390?!

I’m planning our next build and would like to move up from our 4k 4 GPM machine. We probably do 95-99% residential, mostly siding and decks, with some concrete here and there. I was looking into the bigger units, but came across this guy: https://www.3rpressurewashers.com/psi-b-k8025hc.html

8 GPM, 2k PSI and runs off the GX390 for around $2500 shipped. I just wanted to hear if anyone has some thoughts on what I’d be sacrificing to go with a unit like this, as opposed to the larger engines traditionally associated with 8 GPM units. Even though my current unit is 4k PSI, I almost never use it at that pressure. I looked up the pump specs, and ran the calculations online and everything is showing 13 HP is enough to get to those numbers. Any thoughts on whether a larger engine capable of a higher PSI will be better for mostly resi work? Any reason I’ll regret buying this and wish I’d have gone with a bigger setup?

Can’t do concrete effectively at 2000psi, it would strictly be a house washing machine.

Look, I just went through this whole mess a year ago. If you plan to do a lot of resi with concrete, do yourself a favor and find an 8/3000 v-twin of some flavor, at a minimum.

I ran the standard formula and came up with 14.5hp to achieve 8/2000, so the GX390 comes nowhere close to that.

(GPM x PSI)/1100= HP needed

BTW I’m also a window cleaner.:+1:


A vendor that will lie and sell crap like that is a vendor to avoid


Build your own 8 gpm with a predator engine, gear drive and cheap 8 gpm pump for about $2,000.


Even if you’re getting both 8 gpm and 2k psi after loss of pressure due to hose length, fittings, etc you’ll only be getting 1500 psi. Add in the fact that @dcbrock ran the numbers can came up with needing 14.5 hp you’ll be lucky to hit 1k psi. If that combination worked many others would be doing it. There are some running a 5.5 gpm off of a gx390 and they’re getting about 2500 psi. That should show why you’d be lucky to get 2k psi.


If you don’t wash any bricks or concrete that will be fine. But, what kind of house washer cant wash a driveway or front porch steps?

If you are already growing to the point of dropping $2500, you may as well go all the way to 8/3000. You can go the Predator Gear Drive route for the same budget or drop $1000 extra and build your own Honda Gear Drive. 8/1500 sounds too much of a one-trick pony for $2500. Even at 2,000 PSI which sounds highly improbable, that just won’t cut it for concrete work.

$3149 for a Honda GX690 with udor pump (CKC 30/24 8GPM/3500PSI), udor gear box, and Honda muffler all assembled on a skid. Sprayer depot. Have to call to order.


Do you know if they offer financing? Asking for a friend :joy:

I don’t think so. But just save up from your jobs. :slight_smile:

@apexwindowcleaning if you’re already $2500 in, this is a no-brainer.


Super helpful advice, guys thanks a ton! I’ll def just go with a 5.5 or an 8 with a bigger engine that can support it


That’s a really good price, I’m into my 30/24 & Kubota setup for around that and I had to do a ton of custom work. I might do that when I need to expand and hire someone else.

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How is that kubota build coming along? Mounted it yet?

The trailer people are dragging their feet, thinking it’ll be here next week though. I got that thing sitting there with a half-plumbed pump next to it on a can of bondo just waiting. Been running it 5-6 hours a day testing it out without a load, lol. I’M ITCHING TO GET WASHING!!! :smiley:

Edit: I have tested just about every combo of tips on my 12v so far, 40’ is about the farthest I can reach. Getting bored shooting water out of the garage across the lawn.


3R sales is a Great company . They stand by the product they sells

If you’re mostly doing decks and other wood, 8 GPM is too much water. I have one and almost never use it for wood. I use my 5.5 for wood.


I understand using the 5.5 on pickets and other parts of the wood that are more meticulous but say you’re doing a deck that has no pickets and is all deck board would you not want the 8 gpm for that to speed up that process

I find it makes a mess unless it’s an elevated deck. JMO, others may differ. I also price decks so I can take my time. Fences are another story.