8gpm down streaming setup

Im about to take the leap of faith into getting an 8gpm unit. Im going to reserve my 12v for only roofs from now on. I am curious, what setups are you using for down streaming? Im not sure what unloader I need, or what gun is best for that sort of thing. Also going to be using a remote downstream injector. Any advice is very much appreciated.


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GP stainless/kynar injector from Dultmeier. The one with a gray barb on it. Get the proportioning tips recommended for it.

Flowpro.Solutions remote control

K1/zK1 unloader

Suttner 2315 gun

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Yep, I can’t see any reason to change your unloader, or gun, to downstream. I can’t speak on the SS injectors, but I wonder if the innards match (since that’s where they all go bad anyway). We run the brass GP 100776 on all our 8gpm machines. We bucket tested at about 10:1, and we get about $30-40k of work on average before one dies.

Our first FlowPro just arrived yesterday…so we’ll see how that plays out.

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Are you bypassing the injector when not in use? I looked at the one that came w/my machine. It’s a GP 2.3. I did not want to install it because the orifice looks small and afraid it would create too much back pressure and restrict flow.

I may have answered my own question. I have the same injector. I just installed it and there’s no loss of flow. Just goes to show how much water can go through a tiny orifice. There’s a lot more distance just coming out of the ball valve but on the gauge there’s no added pressure. It’s pulling soap w/250 ft. of hose. I may try w/300ft 'cause I have a lot of ground to cover in the next few days.

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I highly doubt that. I use my 12v all the time when downstreaming isn’t cutting it.

Yeah, the flowpro remote bypasses the injector. I believe the injector I use (linked above) is a 2.1mm orifice (they sell them labeled in thousandths, for some reason). So it creates some flow restriction.

But the upside is that it pulls a stronger mix than a 2.3, and I don’t have to worry about still pulling soap with 350+ feet of hose.

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It’s surprising how much water can go through. With the 2.3 I was still getting the 8-8 1/2 gallons. Some of the giant industrial pumps do hundreds of gallons per minute through just through a small pipe. There’s a chart somewhere on this forum about that. Makes me wonder about all the upsizing on hoses.

I use a 2.1 with my 8gpm for max draw…which isn’t saying much. When I take it off for surface cleaning there is a noticeable difference, the SC wants to lift off more.

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I slapped a 5.5 gpm 12v together a couple weeks ago & used an adapter bushing to downsize the output from 1/2 inch to 3/8 so I could use my pressure hoses. Through 100 feet of hose with the ball valve wide open, 2.6 gpm. But then again, it’s only 60 psi.

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Friction loss is a function of diameter and length. 2.3mm through a tiny distance is ok (it does reduce the pressure by a few hundred psi, but flow is not really lost as long as it’s not generating enough pressure to cause a partial bypass situation.)

But if you tried to force 8gpm through 200’ of 1/4” hose instead of 3/8”, you would be losing hundreds more psi at the gun, and it would more than likely prevent most downstream injectors from pulling soap due to all the back pressure. You might even lose some flow due to the partial bypass issue I mentioned above.


Switching to the 2.1, you’ll lose about 1gpm flow running thru the injector, but you’ll pull probably 10-20% stronger mix. About the only time I ever bypass my injector is doing surface cleaning.


Just curious, how are you turning off your soap when not bypassing?

Ended up going with something similar based on your comment, forgot to thank you!

I went with the unloader from the factory, seems to be decent enough. Suttner 2315 gun and a 2.1 dual draw injector for soap / SH, and a flow pro box.

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