Overkill electric pressure washer - school me

[86turbodsl]

I'm looking to build an electric pressure washer. I have industrial controls experience, and lots of power at my home.
I would like to build a pressure washer for a wall mounted, heated cabinet in my house attached garage, where i typically do
vehicle washing. Is there any recommendations for a very high quality pump and a horsepower requirement to run it? I know
electric drive tends to be lower gpm / pressure, but i have ability to run higher HP motors on my electric service.
Ideally, i'd have a pump that monitors line pressure and shuts down at pressure like my graco paint sprayer. Suggestions on flow/pressure
are great.

 

[danski0224]

You will probably be limited by the available power.

You should figure out how big of a motor you can power, then that will limit your pump choices.

 

[strutaeng]

Well, I built one myself about 6 years ago. Had a 5 HP TEFC Baldor laying around and wanted to find a use for it. Bought a CAT belt drive pump, a sheave, 2 belts and unloader valve. The pump manufacturers have some basic equations for PGM, PSI, HP and rpm. That's how I calculated mine.

I think mine is like 2.5 GPM @ 2800 psi. Thing is a beast. You really need to use with both hands, otherwise it wears out my hand out with one grip. Mine is on a misc. steel frame on a service cart. It's heavy!

I don't use mine too often, mainly to wash engines and transmission cases.

 

[86turbodsl]

Well, I built one myself about 6 years ago. Had a 5 HP TEFC Baldor laying around and wanted to find a use for it. Bought a CAT belt drive pump, a sheave, 2 belts and unloader valve. The pump manufacturers have some basic equations for PGM, PSI, HP and rpm. That's how I calculated mine.

I think mine is like 2.5 GPM @ 2800 psi. Thing is a beast. You really need to use with both hands, otherwise it wears out my hand out with one grip. Mine is on a misc. steel frame on a service cart. It's heavy!

I don't use mine too often, mainly to wash engines and transmission cases.

Got any pics? I have a 50kVa transformer all to myself. 200A on the house, 200A on the shop. Overkill is my middle name... lol.

 

[mike93lx]

Even the biggest electric units can't touch what gas can do, but maybe you don't need that much power. For car washing, 5hp is more than enough, but if you were doing real surface cleaning, or drain jetting, gas is 100% the way to go.

Northern tool has a decent selection of electric units. That should give you an idea of what pressure and flow levels are possible

 

[PoorUB]

I have a pressure washer that originally had a 5 HP electric motor. I was rated a 4 GPM @ 2,000 PSI. The last few years it seems higher pressure and lower GPM is more common.

Any way, I pulled the motor and put it on the air compressor as I didn't use the pressure washer very often and it sat for a couple years. Then one day I got a free 8 Hp Tecumseh engine so I bought a pulley for the engine and mounted it on the washer. When swapping from electric to gas most places say to double the Hp so the 8 HP is a little lacking so I turned down the pressure a bit, but I am thinking it is about 1800 PSI and 3.5 GPM. Still does what I need an it is more portable with the gas engine.

I have been on the look out for a cheap 10 HP engine but I really do not need the extra pressure or GPM.

Most pumps will have pressure/GPM/HP ratings.

 

[strutaeng]

Got any pics? I have a 50kVa transformer all to myself. 200A on the house, 200A on the shop. Overkill is my middle name... lol.

It's kinda ghetto and been outside for some years. I think at some point I said to myself it was going to get a magnetic contactor...

 

[sherrillkelby]

There's a popular belief amongst car detailers that around 1K PSI is safe for paint, and you want a high flow rate. As far as I know, this was popularized by Obsessed Garage, a detailing supply retailer and YouTube channel, so it's not a scientifically determined number or anything. He sells Kranzle as a commercial solution, also some other brands that do around 1k PSI and 2 GPM.

 

[MileHighRover]

1,000 to 1,200 psi is perfect for car washing. 2 gpm is about the standard goal for home use. Obviously more gpm isn't a bad thing, just most residential users are looking for something to run off 120 so that's the limit.

For you I'd get a CAT Pumps (not the heavy equipment brand) or General Pump brand pump with 3-3.5 gpm. You'll have to run that off a 240 motor. Direct drive is most common or you could go belt drive. You may have to have a mag starter depending on the HP requirements to get your desired flow. Your pump will be rated higher than 1,000 to 1,200 but you can bring the pressure down with a larger nozzle, which is the correct way of doing that versus adjusting the unloader. You'll also want to add auto start/stop to the system, either by way of a pressure switch or flow switch.

You're probably looking at $2,500 or so for that setup. Of course you'll need to add a wall mount, hose, trigger gun and a lance if you'd like. A hose reel makes things easier as well. All in you're in the $3,000 range.

There are plenty of wall mounted pressure washers already built with those PSI and GPM specs. Plenty of places online that sell them, too. With a lower quality pump and motor you can be in the $1,700 - $2,000 range.

I have a CAT 430 pump rated at 1,000 psi and 5 gpm. I have it set up to push 3.1 gpm at 1,000 psi. Running mine off 240.

Here's a bunch of reference material with nozzle charts, HP charts, etc. CAT Pumps Reference Documents

 

[MileHighRover]

Here's an example of one with good specs. No mention of pump brand, though. Pressure Pro

 

[86turbodsl]

Excellent. I'm a pretty good scrounger with a lot of industrial parts sitting around. I can do 240 easily, i'd run a new line to the garage. Pretty much the pump and the drive is what i'd have to buy. I am swimming in 5hp 3ph motors.

 

[86turbodsl]

Here's an example of one with good specs. No mention of pump brand, though. Pressure Pro

That's a nice looking unit. i was thinking if i used a pressure sensor and drive, i could maintain the pressure and use the drive to throttle down the output as needed to maintain the pressure. I have spare PLC's. I could avoid the mag starter also. 5hp drive might cost a bit though.

 

[86turbodsl]

It's kinda ghetto and been outside for some years. I think at some point I said to myself it was going to get a magnetic contactor...

Have you had any issues with the side loading on the belt drive of the pump? I'm more a fan of direct drive for pumps, but maybe it's not that big an issue. Trouble is most manufacturers don't publish data on allowed side loading, which leaves it open to design interpretation.

 

[86turbodsl]

1,000 to 1,200 psi is perfect for car washing. 2 gpm is about the standard goal for home use. Obviously more gpm isn't a bad thing, just most residential users are looking for something to run off 120 so that's the limit.

For you I'd get a CAT Pumps (not the heavy equipment brand) or General Pump brand pump with 3-3.5 gpm. You'll have to run that off a 240 motor. Direct drive is most common or you could go belt drive. You may have to have a mag starter depending on the HP requirements to get your desired flow. Your pump will be rated higher than 1,000 to 1,200 but you can bring the pressure down with a larger nozzle, which is the correct way of doing that versus adjusting the unloader. You'll also want to add auto start/stop to the system, either by way of a pressure switch or flow switch.

You're probably looking at $2,500 or so for that setup. Of course you'll need to add a wall mount, hose, trigger gun and a lance if you'd like. A hose reel makes things easier as well. All in you're in the $3,000 range.

There are plenty of wall mounted pressure washers already built with those PSI and GPM specs. Plenty of places online that sell them, too. With a lower quality pump and motor you can be in the $1,700 - $2,000 range.

I have a CAT 430 pump rated at 1,000 psi and 5 gpm. I have it set up to push 3.1 gpm at 1,000 psi. Running mine off 240.

Here's a bunch of reference material with nozzle charts, HP charts, etc. CAT Pumps Reference Documents

Any issues feeding the pump with house hot water? Or even "warm" water? Would help the cleansing/sudsing ability of the washer. I could put a thermostatic valve on the inlet to maintain a temp. I'm going to deep dive into the doc you sent now...

 

[theoldwizard1]

A "general purpose" PW needs about 4 GPM. To get that you will need at least a 2 HP motor, maybe 3. Both will need 240V to deliver that power.

 

[theoldwizard1]

Any issues feeding the pump with house hot water? Or even "warm" water?

I don't know, but every PW pump I have seen says "cold water only" !

 

[strutaeng]

Have you had any issues with the side loading on the belt drive of the pump? I'm more a fan of direct drive for pumps, but maybe it's not that big an issue. Trouble is most manufacturers don't publish data on allowed side loading, which leaves it open to design interpretation.

"Side loading?" Not sure I'm following you there... Like the trust loading from a gas engine?

No issues that I'm aware of...

I once rented a large Bobcat-type machine to excavate for a retaining wall project at THD. They required that the machine be "as clean as I received it." I used the PW to wash the thing...took like 30 minutes, maybe longer at full blast. The motor was barely warm. Don't rent tractors from THD BTW.

It would be nice to hook up a clamp-on ammeter and see what the actual amp draw is.

I originally thought I was going to use it to wash my vehicles, but I think it's overkill. I "suspect" that high of pressure may be bad for the vehicle finish, maybe depending on the nozzle used? It's considerably stronger than my local drive-up car wash.

 

[MileHighRover]

Any issues feeding the pump with house hot water? Or even "warm" water? Would help the cleansing/sudsing ability of the washer. I could put a thermostatic valve on the inlet to maintain a temp. I'm going to deep dive into the doc you sent now..

Each pump will have the inlet water temp specs. Most of your name brand pumps will be 140 degrees. CAT Pumps have high temp seal kits available for most of their pumps that push that to 190.

 

[MileHighRover]

Have you had any issues with the side loading on the belt drive of the pump? I'm more a fan of direct drive for pumps, but maybe it's not that big an issue. Trouble is most manufacturers don't publish data on allowed side loading, which leaves it open to design interpretation.

Those pumps, like mine as well, are made to be belt driven. So there's no issues with side loading as long as you stay within the HP requirements of the pump. I'd imagine there could be some issues if you used a higher HP motor than is recommended.

 

[MileHighRover]

A "general purpose" PW needs about 4 GPM. To get that you will need at least a 2 HP motor, maybe 3. Both will need 240V to deliver that power.

The GPM of a pump is just half of the information needed to determine HP requirements. The formula for HP needed is GPM*PSI/1460. So if your pump is putting out 3,000 psi at 4 gpm, you'd need just over 8 HP to run it.

 

[86turbodsl]

In the past i've read that gpm is much more important than pressure, and with the fine finishes on cars, i'd tend to want to keep the pressure lower. I calc'd out about a 3hp motor for the flow and pressure i'd want. That's easily do-able on house 240V.

 

[86turbodsl]

Each pump will have the inlet water temp specs. Most of your name brand pumps will be 140 degrees. CAT Pumps have high temp seal kits available for most of their pumps that push that to 190.

My house hot water is about 140F so thats' about perfect i think.

 

[mike93lx]

In the past i've read that gpm is much more important than pressure, and with the fine finishes on cars, i'd tend to want to keep the pressure lower. I calc'd out about a 3hp motor for the flow and pressure i'd want. That's easily do-able on house 240V.

Yes, GPM is what really matters. High pressure with low flow will do damage and clean poorly

 

[blazemaster83]

I work on big boats, the pressure washer at work is 7.5hp 3 phase motor, 4000psi, 4gpm. it still takes some effort to get all the bottom growth off. I have a machine shop at home with 3 phase tooling and have thought about building one with the same specs at my shop. It would be nice to just walk up to it, grab the hose and turn it on. Not have to fuss with a gas engine, no oil change, noise, starting problems.

 

[86turbodsl]

I'm betting your boat growth is a lot tougher than road grime once a week.

 

[MileHighRover]

GPM is king. You'll have no problem putting together a very nice machine that will suit your needs perfectly.

 

[MileHighRover]

You'd have to be next level stupid to damage your paint finish with even a 5,000 psi machine. The high pressure is near the tip. Just two feet from the tip and I bet it's a tenth of the pressure.

With car washing there's just no need to fight that kind of pressure when ideally you'll be around 1,000 psi. So lower PSI and higher GPM will make the experience so much more enjoyable.

 

[mike93lx]

@86turbodsl any progress on this project? I've been contemplating a new electric PW and was thinking about this thread

 

[86turbodsl]

Not yet. Lot of irons in the fire right now.

 

[mike93lx]

Not yet. Lot of irons in the fire right now.

But it's been 3 months! Gotta prioritize us, buddy!

 

[86turbodsl]

Lol. Gotta have a car to wash first man...

 

[milkovich]

Any issues feeding the pump with house hot water? Or even "warm" water? Would help the cleansing/sudsing ability of the washer. I could put a thermostatic valve on the inlet to maintain a temp. I'm going to deep dive into the doc you sent now...

Funfact I learned from a chemical manufacturer, the "sudsing" has no bearing on the cleaning ability of the soap but they have to put it in because the customers demand it, just like the fragrance. In fact, more foam may mean a cheaper soap. That said even experienced detailers won't buy a cleaner that doesn't foam or smell good so they have to put it in their products.

 

[86turbodsl]

Wow did not know that

 

[wkndwarrior29]

As mentioned above, you should check out the obsessed garage group and youtube channel. He does a lot of testing and product recommendations specifically for washing cars. You can piece together similar packages on your own a little cheaper. I understand the desire to DIY a unit, but it's hard to justify with what's out there already. Even if you decide to build your own, check out the recommended accessories.

 

[PoorUB]

That's a nice looking unit. i was thinking if i used a pressure sensor and drive, i could maintain the pressure and use the drive to throttle down the output as needed to maintain the pressure. I have spare PLC's. I could avoid the mag starter also. 5hp drive might cost a bit though.

I sold and serviced pressure washers for some time.

I would not bother to stop and start the pump, or ramp the motor RPM up and down to maintain pressure. After all a pressure washer is on and off. You squeeze the trigger and get water, or release it and zero water. Also the typical pressure regulating valve just works with zero issues.

The one thing I might consider is a flow switch and a time delay relay to run the motor. When you drop the trigger on the gun, the flow stops, times out 30 seconds and shuts off the motor if the trigger is not squeezed again. You can drop the wand, walk away and the pressure washer shuts off. An hour later you walk back, grab the wand, squeeze the trigger and it starts up on it's own. I would still put on a main on/off switch to kill all the power.

 

[86turbodsl]

Great idea. I can use the pressure switch and plc to time how long it sits on the prv and shut down after a time. I used an old graco like that back in the day. It would only run when the trigger was on. Just like the graco paint sprayers. It was pneumatic drive though.

 

[insidethehoax]

There's a popular belief amongst car detailers that around 1K PSI is safe for paint, and you want a high flow rate. As far as I know, this was popularized by Obsessed Garage, a detailing supply retailer and YouTube channel, so it's not a scientifically determined number or anything. He sells Kranzle as a commercial solution, also some other brands that do around 1k PSI and 2 GPM.

People saw some guy on YouTube who has a couple of bucks and was able to fool viewers in to believing that he was something that he is not. That is where the those figures came from. He used 1000psi because he said at that psi his hand would hurt when putting it in front of the pw gun therefore if it hurts his hands that must mean it hurts the paint. I wish this weren’t the case but I’m not lying. Realistically anywhere from 1200-2500psi and 1.2-2.0gpm is perfectly fine.

 

[86turbodsl]

@86turbodsl any progress on this project? I've been contemplating a new electric PW and was thinking about this thread

Made some progress on this. I bought an ancient triplex pump locally, it's huge. It was labeled as a "Whisper washer" by commercial mechanisms, inc. It's got a 1.116" bore and 0.75" stroke on each cylinder. The valve head is solid brass, and the valves are stainless. O-rings on each cylinder. The volume of the pump calcs out at 0.0095 gal/rev. So 3gpm is 315 rpm. Belt drive is obvious. I have to figure out the horsepower needed and get a motor and drive to suit. I am fairly sure i will shoot for about 5 hp on 240v and variable speed drive to match pressure sensor. I am thinking 1000-1200 psi target and vary speed as needed to match nozzle.

 

[MileHighRover]

Nice. Looking forward to the end result.

 

[Ing3018]

Here is an online catalog I have used to find pressure washer components. https://www.epageflip.net/i/1344445-2021-nilfisk-hpw-parts-accessories-catalog/0?