Pics of my 5HP DIY electric power washer

[Dan Friedrichs]

Didn't want to hijack John's thread, but thought some might be interested in this.

5HP Baldor motor - $400
Hypro 2300 triplex ceramic piston pump - $300
Lovejoy coupler between them, covered with a 3D printed shield
General Pump ZK1 unloader valve - $100
Magnetic starter - $100
Pressure gauge, over-pressure pop off, inlet filter, etc
All bolted to a piece of 1/4" steel with wheels on the back
40' hose on a Sampson hose reel
MTM gun, all connectors stainless

2500psi, 3GPM, can run up to 160F hot water
Aside from the stupidly-expensive hose reel, I think I have <$1k in it
Just press the green button to go, press red button to stop - no gas, no pull starting, no fumes
Sits in my garage and never moves - I have an extension hose long enough to get to the back of the house

[Michael Schuch]

Nicely done, I like the way it is integrated in a single compact package. 2500psi, 3GPM is what my Sun Joe pressure washer is rated at too... I bet yours probably puts out 3 times or more cleaning power than mine with its cheap universal motor, even cheaper low end pump and imaginary specs from the marketing department.

Does the motor run constantly while the washer is powered on? I thought (I could be wrong) that the unloader valve bypasses water from the high pressure side to the intake when the wand valve is closed leaving the motor (engine) running constantly? I ask because I have a couple of TEFC motors sitting around and haven't figured out how to turn the motor off when the wand valve is closed. I figured the little plastic pressure washers like my Sun Joe just used a pressure that shut off when it hit a particular psi which then shut the motor off.

[Dan Friedrichs]

Does the motor run constantly while the washer is powered on? I thought (I could be wrong) that the unloader valve bypasses water from the high pressure side to the intake when the wand valve is closed leaving the motor (engine) running constantly?
Yep, correct. The General Pump ZK1 is a "flow sensitive" unloader, so when it detects that water has stopped flowing out the wand, it bypasses it back to the inlet (in the side-view pic, you can barely see the bypass hose exiting the bottom of the unloader and routing back to the inlet). In bypass, the pump is hardly doing any work (just circulating water at low-pressure), so the motor is just loafing.

[Bill Dufour]

My Landa is like this but direct coupled. You are not supposed to let the pump idle more then a few minutes or it will overheat the water.
Bill D

[Tom M King]

Looks good! That's a good pressure for working on a house, and the flow rate is not enough to wear you out, but still can get a lot of work done. My 2500 4.4gpm one is quite tiring to run for long periods. Are you running 3.0 tips?

We never close the trigger with the pump running for more than a few seconds at the time. A remote for an electric would be a good thing to have. The Briggs and Stratton motor wore out when the pump was 19 years old, and I've never done anything to the pump but change the oil and put RV antifreeze in it over the Winters. It's a belt driven pump.

[Dan Friedrichs]

Yep, orifice size "3" tips.

I've not been too worried about leaving the motor running with the trigger closed and it in bypass mode. I've put a small thermocouple in the bypass line and watched if the recirculating water temp goes up (it's a small volume of water, after all), and it really doesn't. There is a spring-loaded pop-off valve on the high-pressure outlet that would open if something bad happened (e.g. water getting hot enough to boil).

[Curt Harms]

Nicely done, I like the way it is integrated in a single compact package. 2500psi, 3GPM is what my Sun Joe pressure washer is rated at too... I bet yours probably puts out 3 times or more cleaning power than mine with its cheap universal motor, even cheaper low end pump and imaginary specs from the marketing department.

Does the motor run constantly while the washer is powered on? I thought (I could be wrong) that the unloader valve bypasses water from the high pressure side to the intake when the wand valve is closed leaving the motor (engine) running constantly? I ask because I have a couple of TEFC motors sitting around and haven't figured out how to turn the motor off when the wand valve is closed. I figured the little plastic pressure washers like my Sun Joe just used a pressure that shut off when it hit a particular psi which then shut the motor off.

If I understand correctly, you might not want to start/stop a TEFC motor that often. Dust collectors with TEFC motors usually have a limit of 4 - 6 starts/hour. Universal motors don't have the same limitation I don't think.

[Tom M King]

If you need some flow in between tip sizes for 3.0 flow, you can find that by using tips with different flow rates. For instance if 25 degrees is too strong, but 35 degree not strong enough, you can use a 35 degree tip in a lower flow rate. The fan width is the same, but the orifice is smaller, so it comes out a bit stronger.

[Kev Williams]

Reading this thread has lead me to read up on how these pumps work, especially how they bypass water when not spraying. I got a kick out of the horror stories about running or idling for extended periods while not spraying because of the 'heat buildup'. The 'act' of pumping water DOES heat the water. I can testify to that, years ago our then-teenage kids left our new hot tub running for 8 hours (they bypassed the 10 minute timer), and the water temp went up to 115° just from the pumping friction. However, simply moving water around the insides of a relatively smooth-walled pump at ~1gpm isn't under anywhere the friction that's imposed on water being moved at ~13gpm via a 3200 rpm centrifugal impeller blade...


I've not been too worried about leaving the motor running with the trigger closed and it in bypass mode. I've put a small thermocouple in the bypass line and watched if the recirculating water temp goes up (it's a small volume of water, after all), and it really doesn't.
--real world proof-- :)

I've left my washers running for up to 1/2 hour several times because of phone calls & such. I've only had one ever problem with a power washer ever, and that's with the *!^&% that stole it out of my truck...

[Michael Weber]

That’s an impressive build demonstrating lots of different skills. Good job.

[Michael Schuch]

If I understand correctly, you might not want to start/stop a TEFC motor that often. Dust collectors with TEFC motors usually have a limit of 4 - 6 starts/hour. Universal motors don't have the same limitation I don't think.

That is a very good point that I had not considered!

I have a 1ph 5hp C-Face TEFC motor I was considering using but I can see how many starts could cause an issue if it stops via a pressure switch. I also have a couple 3ph TEFC motors that I was considering controlling with a VFD. I don't see much need for variable speed but soft starts as well as a bit of intelligence in the motor control sounds attractive. The Fujitsu VFD's I have allow for a fair bit of configuration. Maybe use a thermal switch to shut the motor off if it idles in bypass for to long?

I gave up on the idea of making my own and recently purchased a cheap Sun Joe so I don't have an immediate need to build another power washer so my interest is more academic at this point.