Help replacing chem injector


Just recently purchased a little trailer rig and doing some repairs. The downstream injector was not working at all, so I’m looking to replace it. However I can’t find anywhere that sells this specific injector.

Here are some images of the piece:

As you can see, this part has the typical chemical injector valve that I’ve seen in images and videos, but there’s also this additional valve that fits into the pump. I have no idea what this secondary valve does.

I managed to find the product that I believe I have, and it seems to be a “combo” part that comes with both the pressure controller and a chemical injector in one part. Here is the link to that:

My question is; can I get away with just installing a normal chemical injector that doesn’t have that secondary valve? Or do I need to purchase this exact part? I’m not even sure where and if they sell just the injector for this setup.

Any advice here would be very much appreciated.


In short, yes. But, let me do you one better and offer a suggestion:

If this is a 2 wheel roller unit, get a 2’ piece of whip line and add the injector at the end, prior to your full length hose, and match the qc’s accordingly. This is how I have setup my auxiliary unit (4gpm/4200 psi) and it works like a charm.

This will move the chemical away from backsiphoning into your pump and damaging it with corrosive SH.

If this unit is mounted and you have a hose reel, install the injector right at the swivel of your hose reel, or just prior. (Super swivel is most resilient to this configuration)

This is the setup I have run for some time, mixing my chem/surfactant in a 5gallon bucket right at the site of the injector. Simple, and it works. Main rig 8gpm/3500 psi.

It’s about matching your gpm to your injector/proportioner.

Image of auxiliary injector attached

That isn’t necessary. It is impossible for soap to back feed into the pump

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I wonder why there’s so much literature out there about distancing your ds injector from your pump?

I will continue to have mine at the swivel for my hose reel since that setup works for me.

If SH somehow overcomes the force of the water flowing through your injector and hose and makes its way into your pump then it was preordained. The reason we place our injectors further from the pump is to limit the turbulence at the injector so that the Venturi effect can do it’s thing. Has nothing to do with back siphoning at all.

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Further from the pump allows the steam to straighten before it enters the injector. The homeowner model in the pic isn’t going to make much difference where the injector is. Distance of the injector from the pump has zero to do with it back feeding into the pump

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Basically what @DisplacedTexan said. I didn’t read his part before I posted

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Thanks for the replies!

So, from what I’m gathering, there is no need to worry about that little secondary valve on the old downstream injector, and I can simply attach a new injector where the old one was? What about that o ring that’s almost dissolved on the right side of the old injector? If I just stick a regular old 1/2" brass in there where that used to be, will that be okay?

Also, I recently purchased a new injector from Northern Tool, but it has 3/8 fittings on both sides (the fitting on my pump outlet is 1/2"), so I was thinking of getting a 1/2" to 3/8" adapter to go from the pump to the injector.

Thanks again @Innocentbystander @DisplacedTexan

I’m not really saying that. I would replace the pressure washer before I messed with the injector. Your injector is probably ok anyway if you just reset the spring and ball in the intake.

Glad to help. You basically just need to delete all of the external stuff off of that unloader and plug those ports with brass plugs. Or, replace the unloader altogether with another VRT3 (may be a good idea since you picked it up used) and it will come with those ports already plugged. After you get that squared away, put a 3/8" stainless steel nipple on the “out” port and run your whip line to your injector and from injector to swivel on reel. And Voíla you’re rocking and rolling. But, yes, you can just run a standard injector like you bought at Northern Tool. I’ll shoot you some pics of how mine is. It’s incredibly basic and very similar to what you have.

It’s dark so the pictures are awful but you should get the idea.

Here you can see the outlet side of the pump with a short whip line running to my unloader block.

Then you’ll see the unloader with only two ports in use. The bypass hose to my buffer tank and the whip hose going to my injector at the reel.

Nevermind the leaves. It’s a daily battle.

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That first photo does not want to play ball. Give me a second.

I wouldn’t suggest that the chem would travel against the flow of the unloader while in use, but I don’t think it far fetched that chemical could be in the line/injector once the machine is shutdown, and find its way into the pump. Regardless, placing a ds injector right by my pump is not a move I am going to make.

Hey man,

I really appreciate you helping me out. Those pics are putting things into perspective for me.

So from what I understand, your main water outlet is plugged directly into the unloader, and the injector is all the way down the line just before your reel. Also, you have a bypass hose coming out of the side of your unloader, which cycles cool water through your pump constantly.

I’m definitely going to be copying your setup if I can. My trailer is a little smaller so things are going to be a bit more crowded but I think I can make it work.

One last thing and I’ll leave you alone; is that a filter you have on your intake line from your tank? If so, how necessary is it to have that? It seems like a good idea just to be on the safe side and not have random ■■■■ get in your pump. Might I ask what kind of filter that is?

Thank you!!

People that do this for a living will rinse their injector after each use. There’s nothing left in the line when the machine is shut down. It’s simple as that. So, no, there is no back siphoning and you’re worrying about something that won’t ever happen. No one ever suggested to place your injector at the pump. It must always go downstream of the unloader. All I’m saying is the whip line has nothing to do with back siphoning because that doesn’t happen. Got it?

I’m sure you can make it all fit. There’s plenty of folks on here running micro trailer builds or even out of a short bed truck. You’ll be fine. Yes, you absolutely want a filter between your buffer tank and your pump inlet. That’s a 1" inlet and outlet mesh filter. You can pick them up at Tractor Supply or other farm stores. Or you can order the clear ones online so you can see when you need to stop and clean your filter. I have a clear one but have been too lazy to change it out. I think I clean my filter about once a month and it’s never really that dirty.

Jeez man. Die on that hill. It may come as a shock, but I do this for a living too. Full time. Nothing else. For years. As someone else said on another thread, just because someone does something different than the way you do something, doesn’t make them wrong. Just offering help on a forum that people go to for help. Got it?

Nothing wrong with the way your doing it. Nothing wrong with using a whip line. Just trying to curtail the bad advice that it can back feed into the pump, that’s all. Make a ton of money and do what works for you.


There’s no hill to die on, bud. You made a statement that made absolutely no sense and multiple people informed you that you were wrong. It’s as simple as that. Since you’ve been doing this for years you should already know this stuff. Rinse your injector and then the only thing left in the line is clean water. Day one stuff right there.

You have a very fragile ego. Nowhere in my post did I imply that you were a newbie or that you didn’t wash for a living. Take that thin-skinned crap on down the road, hoss.