Dewalt 4gpm Pw powered by Honda Triplex pump

Just purchased a 4gpm Dewalt PW/Honda/triplex pump. It says it has a downstream chemical injector. Should I purchase one? I see everyone has 1 and yet there machines are bigger & nicer than mine

return it while you still can… use the search tool at the top right of your screen


Thanks Juan, I tried searching I couldn’t find. So your saying the downstream I have with the unit is fine? why does everyone say to buy one

Joined May 26, '18

Read 4h (29m recently)

You aren’t spending enough time searching. I’ll sum it up for you and you can continue to search from there. The one on your machine isn’t gonna cut it. I hear it won’t pull with over 50ft of hose and you’ll only get about a 20-1 ratio which is not enough. Remove it by unscrewing it, taking out the the orifice, and plug the hole. You can then buy a downstream injector and get at least a 10-1 ratio. Including what I just said, all other information you need is on this forum already. While you search you will find answers for questions you didn’t even know you had. Good luck.

Yep. Awful machine. Search dewalt or Simpson. Identical machines. Garbage.

I’ll say it again, return the machine you have now if you still can and then proceed to spend at least a couple of days on here reading. If you cant return the machine, follow @Max1 advice.


I wouldn’t say ‘garbage’, my Simpson is a GX 390 and Cat pump, 4/4. Granted General pump would be better but I’ve put my machine through it’s paces and it works quite well for what it is.

But I agree, probably best to try and get a belt drive washer now and be done with it.

Max said it though, if you plan to keep that machine unscrew the existing injector, take the orifice out (do NOT unscrew the injector hose barb) and install the GP injector. Did that on mine, works very well.