As I see it, the biggest problem you will have is supply. Two machines drawing 4 gpm at the same time would be a problem at some homes I do. (99% residential with 8 gpm/3000psi.) Many times, a customers city water supply will not keep up with 8 gpm, so I usually carry 75 or so gallons in my 300 gal tank as a buffer. If the flow is low, I will allow the tank to fill while I get set-up. Sometimes, you have to give it quite a head start.

In fact, insufficient water supply may be the reason you are having problems with your machines now. Starving a pw is never good for it. Direct drive pumps, because they are spinning at the same speed as the engine (3400 or so RPM) don't pull water too well. They need the supply pushed. Belt or gear drive pumps spin at 1/2 engine speed, so they will draw much better - either from a hose bib or a tank.

Having said all that, to answer you question directly, most likely, your guns/hoses and reels are rated to 8 gpm. The psi does not change, only (!) the volume.

John Orr
Low-Pressure Exterior Cleaning
Chesapeake, VA

Myself I would look into the belt drive cold water systems. The direst drive units are good but they seem to have a short life expecially decause people use them at 120% capacity. Gpm is key and the size of the pump is directly related to longevity. If you went with the 5.5 GPM it will make your operation way more flexable. Or run the 5.5 with a 4.0GPM each on thier own unloader and return line and T them together on the outlet side of the unloader with quick connects. Use the 5.5 for rinsing and the 4.0 for chem application and/or heat. put them together for some good cleaning fun!!

If you are trying to get the 8GPM you want I would stay with the 200Gal reserve tank at a min. This will give you 25 min of wash time with no hook up. With a hook up you might get 35-40 before you got low in the water department.

Good luck and shop frugally. What is the going rate for a 10.5 GPM skid mounted unit vs a three piece unit running all the pieces individually.

DAFF

DAFF MOBILE WASH
WINDSOR, ONTARIO CANADA
DAFFMOBILEWASH@AOL.COM

Sorry it took so long to reply.

I started with a Mi-T-M 3505 (which I bought used) and it just didn't sling enough water (4.7 gpm) to get the job done in a satisfactory amount of time. I purchased a BCE HydroMax from Randy and Brian in Georgia which I am very pleased with. I'm shooting 7.5 gpm at 3600 psi through a Mosmatic 21". I still use the Mi-T-M for curb work and rinsing. Future plans include upgrading the pump on the Mi-T-M to 5.6 gpm/3500 psi and replacing the unloader to match--- possibly a KZ-1 flow-type. The 20hp Kohler on the Mi-T-M should handle it fine. Haven't finished all of my research on that yet.

In the meantime, I'm thinking that rigging the Mi-T-M unloader to bypass into the tank instead of the pump will help some with my fluctuating pressure problems.

Big Chief Power Wash
www.bigchiefpowerwash.com
judmorrison@hughes.net
903-445-9268


Tergo, ergo sum ("I clean, therefore I am")