Outdoor Power Equipment and Small Engines - pressure washer plumbing

Hello everyone. This is a re-post..I screwed up and put it in the wrong forum above. Anyway... I have a pressure washer unit with a Honda 6hp on it and a 2500psi crankshaft style Cat pump. It's the DX29 model. I need to know a couple things about how to plumb it correctly. First, it came with a chemical syphon hose barb fitting on it that I won't use alot. Can that remain open when not in use or should it be capped off or put a little ball valve on it? It looks like it would draw in air and cause problems if not closed off when not sucking in additives. All the ones on the show room at Northern have them but none have shutoffs. Store 'associates' where I live know nothing about that. Secondly, some pumps have a bypass type hose between the inlet and outlet for cooling. Again, no help at the store. I do have the temp relief valve. Is that sufficient or would the bypass be a better deal to protect the pump from overheating? Last..pump oil. Straight 30 non det, synthetic (Amzoil) or dedicated 'pump' oil? Which is best? I would like to get it right the first time. It doesn't take long to trash a pressure washer if it's wrong. Thanks in advance for any and all comments.

The siphon nipple has a check ball in it, and won't let pressure spray out. It won't let enough air in to make a difference.

I don't know if the bypass hose is a better working design or not, but both ways work fine. In any case, don't rely on either for cooling. If you aren't going to be pulling the trigger on the wand for more than 30 seconds, then shut the machine off. That's the biggest reason for major pump failure on pressure washers I believe.

I havent seen any test results confirming whether it's better to use SAE 30 syn than regular pump oil. I'd suggest using what the manual says...at least while it's under warranty.

Thanks for the tip on the hose barb ball check. I guess since this isn't a commercial unit cooling is better handled by paying attention to how I use it rather than depending on trick plumbing to do it. I have also stocked up on 'pump' oil and will keep watch on the sight glass. All good advice...thanks Cheese!

With a Cat pump, I'd say it's close enough to commercial quality. Even the commercial ones can't self-cool though. The water has to cool the pump, and the only way for it to do this is to flow through the pump.

Glad I could help!