Combining two PW units?

Hello everyone! A newbie here. But I have a question(s). After browsing the Web for a bit I came across claims and a video of people combining two or more units together to increase flow and or psi. My question is is this a safe operation as far as equipment damage etc.? Is it now a standard operating mode for those without a huge super skid type machine? I currently have a 4gpm 4000 psi unit because I currently don’t do any big commercial jobs (not yet). But let’s say I added another unit in the future for example a 3 gpm 3000 psi. My math says if I combined the two I’m now at 7 gpm and 7000 psi. How would that be safe with a 5000 psi hose? Or would I have to upgrade hoses, wands, spray gun etc? . Any insight would be greatly appreciated. Thanks.

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Only add the gpm not the psi. Average the psi. 4gpm 4000psi + 3gpm 3000psi= 7gpm 3500psi

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The psi falls to the lower of the two. You are correct that the gpm adds up.

Thanks Bucket Bobby thanks Tim. I’ve seen several very low cost belt drive units locally for sale. Prices are cheap enough that it takes the most of the risk off buying a used unit. I’m gonna look into this and see where it goes. Thanks again for the info.

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Something else came to mind. With the two unit set up. If at times I only wanted to use one. For example to wash a patio furniture, car etc. Is it as simple as not running one unit and shutting off a valve. Or would I need to readjust the unloader valves and all sorts of other components?

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Something else came to mind. With the two unit set up. If at times I only wanted to use one. For example to wash a patio furniture, car etc. Is it as simple as not running one unit and shutting off a valve. Or would I need to readjust the unloader valves and all sorts of other components?

Sent from my SCH-I545 using Pressure Washing Resource mobile app

Sent from my SCH-I545 using Pressure Washing Resource mobile app

A properly set up Siamese kit will allow one unit at a time.

A properly set up Siamese kit will allow one unit at a time.

Get a siamese kit with check valves. Hooking two machines together is awesome. Just remember to keep your ball valve open or keep the trigger pulled until both machines kick in, or one of the machines will stay in bypass mode.

Good advice. Thanks Ralph

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I just recently went through all of this. It was a pain and kinda expensive but it was well worth it. I bought 2 high pressure valves(3/8). Then went to a hydraulic shop and had them make up the hoses and the Tee. It cost me about $140 for 15ft of hose and the ends pressed on. That was the tee also. No the check valves. You will need to use 1/2" hose instead of 3/8 because of the reduction of the size in the inner tube. 1/2 won’t restrict your flow. But max PSI for my 1/2 hose is 4100 psi.

Why didn’t you just buy the siamese kit from Russ. I think I paid $120 with the check valves.

Our siamese kit consists of:
hydraulic grade steel fittings (no brass)
stainless 6,000 psi check valves (again, no brass)
2 wire, 4’ connector hoses (other lengths available)
Hansen brand quick couplers (no chinese sub-standard parts)
For $98.00 plus shipping.

Is there a part number for the Siamese kit?