PSI vs. GPM

#1
I am new in to the business and am in the process of researching equipment. Money is not too much of an issue, so I want to buy a machine that can handle about anything I will throw at it. I am going to be doing graffiti removal, house washing, new construction brick cleaning, decks, flat work, and house washing. I am looking at 2 hot water machines to mount on a trailer. One is a 3500 PSI / 5.6 GPM unit and the other is a 4000 PSI / 4.0 GPM unit. Which one should I get?
 
#2
Supply not being a factor, more gpm is better. Will you have a water tank? If yes, then the 5.6, If not, I would go for the 4.0. The reason being that many times you won't be able to get more than 4 or 5 gpm from a spigot, so without a tank, you will have problems. 4 gpm should be plenty, unless you will be doing a lot of flatwork. More gpm speeds the rinsing factor.
 

Mark

Moderator / Sponsor
#3
Brian,
Welcome to the PowerWashNetwork!

Definitely I would go with the 5+ GPM @ 3500 PSI
unit. I question the 5.6 GPM specification though. :confused:
in most scenarios volume beats pressure.

General Pump rates the TS2021 at 5.6 GPM at 3500 PSI,
I have never seen that pump perform at 5.6 GPM, I am
partial to the AR XW2128 which is rated at 5.5 GPM @ 4000
PSI and will perform at this specification.

Here is a picture of one of our Hot Sellers a 5.5 GPM 3500
PSI trailer package powered by a 20 HP Honda.



Or if you really want a power house we have an 8 GPM @ 3500 unit also:

[hello]
 
E

Ed@PreClean

Guest
#4
John is so very right in saying that you might have trouble getting the volume of water you need at a faucet. My unit is rated at 4.6 gpm and I can suck some faucets off the wall. So I "now", always put water in my tank and do not rely on my float tank.

There are units out there rated at 4-5 even 6000 PSI. Regardless of volume, get one and I hope your a big guy in good shape! I use my unit at 3000psi and after a full day of work my hand and shoulder is wore out. I have a friend who uses a general pump rated at 5000 psi and uses it around 3000. He cranked it up for me to check out the pressure one day and I can tell you no one I know wants to use it all day! BUT

Something else to consider, a unit rated at 3000 psi used at max pressure all the time will wear out faster than say a 4000 psi rated machine used at 3000. Think about it. Most cars can run over a 100 MPH but try doing it all the time, somethings gonna give!

Just my opinion.
ED
 
#5
Right, but when you crank down the PSI (via down throttle or unloader) aren't you also bringing down the GPM?? I was told that you should only decrease PSI by changing nozzles. Thoughts?
 
#6
Kev, as I understand it from my equipment "guy" most unloaders shouldn't be tampered with, but idling down is you best option here if you don't have a dual lance wand.

reed
 

Mark

Moderator / Sponsor
#7
A dual lance / aka: variable pressure lance or
changing nozzles would be best.

I have heard some debate on pros
and cons of running an air cooled angine
at reduced throttle for prolonged periods.

I believe there was some discussion on
this BBS on that subject a year or 2 ago.
 

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