"Dialing back" a 4000 PSI pwasher

G

GraffBuster

New member
I hope this is the right section for this question. And I'm not a contractor, but I might be if I get all this stuff figured out. ;)

Earlier today, I saw this jab by stan in another thread:
My new (Sam's) unit is a 2.7gpm at 2300psi machine and I am gonna clean up Atlanta.
Click to expand...
I had already decided to "go big or stay home," figuring on getting a machine (preferably hot/cold) that will do at least 4 GPM and 4,000 PSI, but that clinched it. :p
Besides being able to blast graffiti off of concrete walls, I was looking at the possibility of some work cleaning crusted cement dust off of covered hopper (railroad) cars. I've seen a recommended minimum of 3,046 PSI and maximum 5,077 PSI for that, so the 4,000 PSI machine should be about right.
From some formulas Paul Kassander posted, I've started looking for at least a 15 HP gas-engine unit. BTW, a trailer won't go a lot of the places my (intended) truck would go, so I'm looking at a skid-mount fed from a 250-gal. "IBC" water tank. Then both the skid-mount and the tank can be hoisted from the back of the truck so the truck can be used for other projects.

And now the real question in all this: can the pressure of that 4,000 PSI unit be scaled back enough to not dent the walls on any future residential jobs? Without shutting off the pump completely, what would be the lowest practical pressure available?

(Let's see what the noob has learned so far: "The zero-degree tip would probably not be optimal for most residential washing." How's that? :D)
Okay, that's one question down, at least nineteen more to go. :p
 
GraffBuster said:
I hope this is the right section for this question. And I'm not a contractor, but I might be if I get all this stuff figured out. ;)

Earlier today, I saw this jab by stan in another thread: I had already decided to "go big or stay home," figuring on getting a machine (preferably hot/cold) that will do at least 4 GPM and 4,000 PSI, but that clinched it. :p
Besides being able to blast graffiti off of concrete walls, I was looking at the possibility of some work cleaning crusted cement dust off of covered hopper (railroad) cars. I've seen a recommended minimum of 3,046 PSI and maximum 5,077 PSI for that, so the 4,000 PSI machine should be about right.
From some formulas Paul Kassander posted, I've started looking for at least a 15 HP gas-engine unit. BTW, a trailer won't go a lot of the places my (intended) truck would go, so I'm looking at a skid-mount fed from a 250-gal. "IBC" water tank. Then both the skid-mount and the tank can be hoisted from the back of the truck so the truck can be used for other projects.

And now the real question in all this: can the pressure of that 4,000 PSI unit be scaled back enough to not dent the walls on any future residential jobs? Without shutting off the pump completely, what would be the lowest practical pressure available?

(Let's see what the noob has learned so far: "The zero-degree tip would probably not be optimal for most residential washing." How's that? :D)
Okay, that's one question down, at least nineteen more to go. :p
Click to expand...

Different nozzles and orifice sizes will determine pressure..

John
 
Gonna clean up Atlanta with that unit? Wow, what is he washing? cant be more than just washing his own vehicle.
 
GraffBuster said:
I hope this is the right section for this question. And I'm not a contractor, but I might be if I get all this stuff figured out. ;)

Earlier today, I saw this jab by stan in another thread: I had already decided to "go big or stay home," figuring on getting a machine (preferably hot/cold) that will do at least 4 GPM and 4,000 PSI, but that clinched it. :p
Besides being able to blast graffiti off of concrete walls, I was looking at the possibility of some work cleaning crusted cement dust off of covered hopper (railroad) cars. I've seen a recommended minimum of 3,046 PSI and maximum 5,077 PSI for that, so the 4,000 PSI machine should be about right.
From some formulas Paul Kassander posted, I've started looking for at least a 15 HP gas-engine unit. BTW, a trailer won't go a lot of the places my (intended) truck would go, so I'm looking at a skid-mount fed from a 250-gal. "IBC" water tank. Then both the skid-mount and the tank can be hoisted from the back of the truck so the truck can be used for other projects.

And now the real question in all this: can the pressure of that 4,000 PSI unit be scaled back enough to not dent the walls on any future residential jobs? Without shutting off the pump completely, what would be the lowest practical pressure available?

(Let's see what the noob has learned so far: "The zero-degree tip would probably not be optimal for most residential washing." How's that? :D)
Okay, that's one question down, at least nineteen more to go. :p
Click to expand...

One of the most versatile pumps I think in the industry is AR's 7gpm at 5000psi,........ respectable flow and all the pressure you need and some. Size your engine and coil at an industrial setting and you will have a killer machine.
 
Maybe so, but there are plenty of people that have that frame of mind.
 
The easy and cheap way to clean with that low gpm and psi is just to stick to small jobs and drink a lot and p*** on it.
 
810f250 said:
One of the most versatile pumps I think in the industry is AR's 7gpm at 5000psi,........ respectable flow and all the pressure you need and some. Size your engine and coil at an industrial setting and you will have a killer machine.
Click to expand...
Thanks for the info; I'll look those up.
 
Before I joined PWI, I thought Annovi Reverbri worked on some of those early Clint Eastwood movies. :p

I just saw one of those pumps on eBay, starting bid $536.50, and another one on Amazon for $610. I had been hoping to find a good used washer for around that price.

Anything with all those heatsink fins on it must have been built for some serious work.
 
I personally have no experience with the AR pumps, but when I was doing research before having my unit built, that was one of the pumps that stood out on paper (theoretically), it looked and had impressive engineering. (Udor pumps too, they have the largest oil reservoir in this pump class 41 oz)

Most manufactures build their machines with pumps they either have a good experience with or that they get at the best volume discount. (that would be mostly the general pump TS2021) The TS2021 is an industry work horse 5.6 @ 3600 psi (tapered roller bearings, nice)

The thing is when you are washing vertical surfaces (houses etc) flow gives you much more speed (it does give you more speed on faltwork too but then you may have more wash water run off to control also). Most of the guys love their 8 to 8.5 gpm pumps (I love mine too General TSF2021)

If you ever used a 4 gpm machine which is almost the standard cold water machine you could appreciate the difference going to TS2021 5.6 gpm.

Ron loves the # 6gpm for flatwork, some guys love their 8 gpms, Dave, and Henry love their 10 gpm pumps.

The funny thing is most may not have all the flow we think we have, because the the pump must be rotated at the manufacturers rpm under engine load to hit the max gpms.

Sorry getting carried away (I love mechanical)....... the other nice thing about the high flow 1750 rpm rated pumps you could run it slower if need be to reduce flow. The pumps most of us use are commercial duty class, to upgrade to industrial duty, it cost 5 to 6 times more for the pumps.
 
GraffBuster said:
Before I joined PWI, I thought Annovi Reverbri worked on some of those early Clint Eastwood movies. :p.
Click to expand...

That is hilarious.

And one of the easiest way to "dial back" the pump is by changing nozzles...as some of the others have mentioned.

Normally you would use a 4.0 tip to maintain your 4 GPM at 4000 PSI. You change that tip to a 5.0 and you are getting 4 GPM at 2500 PSI. If you are using an 8.0 tip you are down to 4 GPM at 1000 PSI.

Another way to change the PSI is with a dual lance wand. They have a handle that you turn that moves the flow from the "working" nozzle to a "dump" nozzle, basically changing the PSI with the flick of a wrist. These are easier in my opinion than keeping up with several different nozzles.

Just please don't mess with the unloader. Not only does that reduce your PSI but it also reduces your GPM. Kinda like cutting your nose off to spite your face. lol. It also puts a lot of back pressure on the pump that can wear it out prematurely.
 
I love it when you talk tech, Nichole!
Rawr!
;-P
 
Nichole said:
That is hilarious.
Click to expand...
Thank you; that and Thad's first reply were the results I was looking for. ("Don't laugh, it only encourages him.") :D

And one of the easiest way to "dial back" the pump is by changing nozzles...as some of the others have mentioned.
Click to expand...
I shoulda known that. :eek:
'Course, it was a long time ago when I last did any real reading on Fire Hydraulics. I'm math-impaired, so I didn't spend much time in that book.

Another way to change the PSI is with a dual lance wand. They have a handle that you turn that moves the flow from the "working" nozzle to a "dump" nozzle, basically changing the PSI with the flick of a wrist. These are easier in my opinion than keeping up with several different nozzles.
Click to expand...
Ah-ha. I've seen those mentioned before, but didn't know just what they did.

Just please don't mess with the unloader. Not only does that reduce your PSI but it also reduces your GPM. Kinda like cutting your nose off to spite your face. lol. It also puts a lot of back pressure on the pump that can wear it out prematurely.
Click to expand...
I promise. Even before you wrote that, I was thinking of the unloader as kind of a safety valve, and I'm not gonna fiddle with anything like that.

Thanks for all the the info. Thanks to 810f250, also. I like mechanical stuff, too--when I understand it. ;)
 
You must log in or register to reply here.
Back
Top