downstream

A

alvarojustino

New member
Hi everyone, I’m about to start a PW business, but I’m still very green. Until I start reading this boards, the only way I knew to apply chemicals was by upstream and pump up sprayer. I read somewhere that downstream cut a lot with chemicals and improve the life of the PW machine.
How exactly does Down Stream works? How is that done? Any help will be much appreciated. Thanks.
 
Downstreaming involves an injector installed on the outlet of the machine and a nozzle to reduce operating pressure. The injector is based on a venturi principle, like the air moving through a carburetor draws gas from the jets. As the water passes through the orifice in the injector, it accelerates into a larger chamber, drawing chemical with it. When you put your high pressure tip in, it backs the water up against a check valve, shutting off the flow of chemical. Once you get the mixture right at the injector, you can call for soap or rinse at the gun. There are injectors available to give you a 5:1 ratio, or 20% chemical strength out the nozzle. Choices for lowering pressure include interchangeable tips, rollover nozzle holders, adjustable nozzle holders, and dual lance wands with 2 pipes coming out of a valve that you use to turn one on and off. Hope I have helped and not added to your confusion.
 
I would like to point out that there is a difference between draw rate and end mix rate.

A 20% draw rate injector means a 5 gpm machine will draw 1 gpm of chemical(s) or 20% of the water the machine pumps.

The end mix % will be a smaller %. It's an easy mistake most folks make and it may not be critical at high dilutions such as 1:25, however, it becomes important at low ratios:

1:5 ratio or 20% draw rate is a 16.7% dilution or end mix %.

Think of it this way:
1 part chemical plus 2 parts water is a total of 3 parts;
1 part divided by 3 parts = 33% or 1/3rd of your mix is chemical

1:2 ratio is 33% end mix
1:3 ratio is 25% end mix
1:4 ratio is 20% end mix
1:9 ratio is 10% end mix
etc., etc.
 
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