Need Advice Using a North Star Pressure Washer

I recently bought a North Star Washer, 3200 psi with a 9 Hp Honda Engine and a Cat Pump. The manual that came with it is very incomplete in explaining the use of the machine. I have used it for some small jobs it seems very well made. I have some questions though. I want to wash my deck with a deck cleaning solution, mine is an oxalate solution. The bottle has several dilutions it recommends but says to refer to your users manual. The manual only says what nozzle to use and to put the siphon hose in the solution. I take that to mean undiluted solution but am not sure. The injector appears to be after the qwater passes through the pump so I am not to worried about damaging the pump itself.
There is also on the top of the pump a "pressure adjustment knob". The manual makes no mention of how this is used. Do any of you North Star owners have advice.
I asked if there was a better manual somwhere and the customer service rep while very nice said wysiwyg.
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I suggest that you abandon the idea of applying the cleaning solution with the sprayer. The cleaning solution needs to reside for a period of time on the deck surface before you pressure wash. I prefer to apply the cleaning solution with a hand sprayer (one that will tolerate the chemicals you're using) and then pressure washing.
3200 psi is quite a bit of pressure if the nozzle is anywhere near the deck. If you aren't very careful you will remove pith from the wood and be left with a corrugated surface. I turn mine down to 800 or at most 1000 psi when working on most wood.
Oxalates are good and appropriate if you have iron (rust) staining because oxalic acid reacts with iron to create water soluble iron salts. I find that most of my deck stains are mold and just plain dirt. For this Clorox (5 or 6% calcium hypochlorite) is enough when diluted at a ratio between 4:1 to 6:1. Commercial deck cleaning products are usually around 10:1 but I find the higher concentration to be more effective. The dirt can be addressed quite effectively by using trisodium phosphate, not the fake TSP sold so often now. The down side of real TSP is that it is like topical steroids applied to fungus...watch them grow! Phosphorous will cause algae to bloom, especially in bodies of water so you need to be very careful. When I use TSP on my deck I first saturate the soil under it with an aqueous solution of lanthanum carbonate. That way most, if not all of the phosphorus is bound up and not available to damage the water in the harbor.
If you really want to hit the mold the addition of a substited phenol, such as is found in Zinsser's Jomax works well to prevent reassurances.
B
Michael Bushey wrote:

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