Chemical Injectors

Soap does most of the work on a house wash, and the chemical injector is what gets it to the wall. Sun Brite Supply sells downstream chemical injectors for machines from 1 GPM up to 8 GPM, plus high-draw acid injectors built for fleet washing and concrete work. Tell us your machine's GPM and we will match the orifice in two minutes. Call 301-519-9274.

How a Downstream Chemical Injector Works

A downstream injector is a venturi. Water leaving the pump squeezes through a narrow orifice, speeds up, and creates a vacuum at a side port. That vacuum pulls chemical up the clear tube from your bucket and blends it into the line. The only moving parts are a spring and a check ball, which is why a part that costs less than a dinner out can meter chemical all season.

The catch is pressure. An injector only draws when line pressure falls, and that happens when you switch to a low pressure soap tip or a large orifice nozzle. Put your high pressure tip back on and the draw stops. That is the design doing its job, not a defect. It also means chemical enters the system after the pump, so bleach and acid never touch your pump packings, unloader, or heating coil.

Sizing a Chemical Injector by GPM

Injectors are rated by flow range because the orifice has to match the water moving through it. A 1.8mm orifice fits 2 to 3 GPM machines, 2.1mm covers 3 to 5 GPM, and 2.3mm handles 5 to 8 GPM rigs. Put a 2.3mm injector on a 2.5 GPM machine and the water cannot build enough velocity through the orifice, so it never pulls. Go too small and the injector chokes flow and robs pressure at the tip. Size for the machine you run today, not the one you want next year.

Hose length is the other half of the sizing question. Back pressure builds with every foot of pressure hose, and most standard injectors pull reliably through 100 to 150 feet. Past that the draw fades or quits. Fixes that work: step up to a high-draw model, run larger diameter hose, or shorten the run. Shooting uphill makes it worse, so budget for that on two-story work.

Not sure what your setup actually lands on the wall? Our free SH Mix Calculator has a Downstream mode. Enter your machine GPM, hose length, and injector orifice and it estimates your draw ratio and tells you what to put in the bucket to hit your target strength on the surface.

Fixed, Adjustable, and High-Draw Acid Models

A fixed injector pulls at one set rate, usually landing between 10:1 and 20:1 depending on your machine and hose setup. Adjustable injectors add a metering knob so you can lean the mix out. Here is the honest counter advice: most pros run the knob wide open and control strength by how they batch the bucket, because bucket mixing repeats and knob settings drift. High-draw acid injectors are the third group. They use chemical-resistant internals so aluminum brighteners and wheel acids do not eat the check valve, and models like the Adams 20% draw far richer than a standard venturi for work that needs strong mix on the surface.

Injector Match-Up by Machine Size

Prices change, so confirm current pricing on the product page or by phone before you order.

From the Field

Treat injectors as a wear item, not a lifetime purchase. Sodium hypochlorite chews on the o-rings, the spring, and the check ball every day you downstream, and a tired check valve is the quiet reason a rig starts leaving stripes. The cheap habit that doubles injector life: drop the pickup tube in clean water for the last 30 seconds of every job and flush the bleach out. Carry a spare on the truck too. A $25 backup injector beats driving off a job that stopped soaping. When one quits pulling, check in this order before blaming the injector: soap tip installed, pickup filter clear, tube not cracked, then pull the injector and inspect the ball and spring. We keep acid-rated models in the lineup for a reason. Standard brass injectors die fast on brighteners and wheel acids, so match the injector to the chemical, not just the machine.

Related Gear for Chemical Application

• SH Mix Calculator with downstream mode for GPM, hose length, and orifice size
• Soap and foam tips that trigger the draw
• Soft wash equipment for roof and siding work
• X-Jet nozzles for applying chemical without an injector
• Foam cannons and foamers
• Chemical hoses and chemical strainers
• House washing chemicals and roof cleaning chemicals
• Quick connects to plumb your injector in and out
• Local? Stop by our Gaithersburg pressure washer store

Frequently Asked Questions

Why is my chemical injector not pulling soap?

Start with the tip. Injectors only draw through a low pressure soap nozzle, so a high pressure tip shuts the draw off. Next check the pickup filter for clogs, the clear tube for cracks, and your hose length. Past 150 feet most standard injectors fade. If all that checks out, the check ball or o-rings are worn and it is rebuild or replace time.

What size chemical injector do I need?

Match the flow range to your machine. A 1.8mm orifice fits 2 to 3 GPM, 2.1mm fits 3 to 5 GPM, and 2.3mm fits 5 to 8 GPM. An oversized injector will not pull and an undersized one costs you pressure.

What ratio does a downstream injector pull?

Most standard injectors land between 10:1 and 20:1, water to chemical, depending on your machine and hose run. Batch your bucket mix around that dilution so the strength on the surface comes out where you want it.

Can I downstream bleach for house washing?

Yes, that is the main reason downstream injectors exist. The chemical enters after the pump, so sodium hypochlorite never touches your packings or unloader. Flush the injector with clean water at the end of each job and the internals last far longer.

How far can I downstream chemical?

Figure 100 to 150 feet of pressure hose for dependable draw with a standard injector. Longer runs and second-story work weaken the vacuum. A high-draw injector or larger diameter hose buys back some distance.

Do adjustable injectors really control mix strength?

Within a range, yes, but the knob drifts and readings do not repeat well. Most contractors run the knob wide open and control strength by how they mix the bucket. Save the adjustment for fine tuning, not for your main dilution math.

How long does a chemical injector last?

Daily bleach users should expect to rebuild or replace once a season. Weekend users get years. Milky or weak draw that a new tip does not fix usually means the o-rings and check ball are done. Call 301-519-9274 and we will tell you if a rebuild makes sense or if replacement is cheaper.