In this article we are going to discuss downstream injectors, covering how they work, some problems we have with them, and how we keep them on the truck so that I can replace them quickly and easily.
We use the general pump downstream injector. It comes with a simple brass piece that we can put quick connects on each end. Quick connects are preferred because, quite frankly, things go bad and these are easy to replace. We typically get 6-8 weeks out of each one. Prices typically range from $15-20 each, plus the coupling, so you're spending about $35 every six weeks, which isn't too bad. There's also a kit you can get, where you can replace the ball & spring in there when needed. I prefer the quick connects, but there are people who prefer the it, so that's another route if you prefer.
The way the downstream injector works is you have pressure coming in, and going out. If you have low pressure going through, around 100 PSI or less, it allows the valve to remain open and will draw soap from the soap tank into your line. If you have high pressure the valve will shut off and no soap will be drawn.
The injectors only go one way. There is a little arrow on the injector that shows you the direction of the flow, and underneath it it shows you how many gallons per minute it is, and what size the injector is. You want to make sure your flow goes with the arrows. If you go the other way, you will not get soap and it will not work.
What are some issues we have with a downstream injector? If the hose that goes back into your tank gets pinched, it won't work. If the hose gets a hole in it, even a tiny one, it won't work. If any of the plumbings in the fittings on the tank get a little leak, it won't work. Anything that causes it to suck even a tiny bit of air into it, and it will not work.
How do you know if it's sucking air? One way to test this is to pull the hose off and pull the trigger on the gun. If you put your finger on there you should be able to feel if it's sucking on your finger. If it is, then you don't have a problem. If you don't feel it sucking on your finger then that means the ball valve is either gone or stuck, and usually if it's stuck it's about to go bad anyway. If the ball is stuck, then while you're pulling the trigger you can take a small item like a nail and push the ball down and you should hear it sucking again.
The ball & spring in the downstream injector is made out of metal. We use sodium hyprochloride, which will rust metal, another reason they usually don't work that long.
Now, some people prefer to use an X-Jet. They do last a long longer, but the cost is about 10x what you will pay for a downstream injector. An X-Jet will last you 2-3 years, but you also have to carry your bucket & hose around with you. With a downstream injector we can keep it all on the truck and not have to carry it around. That's why we prefer the downstream injector, but you do have people who swear by the X-Jet, as it is a good quality tool.
A downstream injector will get you one gallon of soap for every 10 gallons of water, but we're also diluting in our soap tank as well, so while we start with 12% sodium hyprochloride, we're only using about 0.75% when we actually clean, which is how we can clean around a house and not kill the landscaping.
An X-Jet can go stronger than a downstream injector. If you're doing mostly vinyl siding, a downstream injector is all you need. If you do a lot of stucco or brick, then an X-Jet might work better for you because it can go up to a 3:1 ratio on the soap, and you can put a pretty strong mixture in there, which is what is needed to kill the algae, molds, and other growths in those materials because they are more porous than siding.