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Whats wrong with my water pump setup?

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#1 sahrcar


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Posted 23 May 2011 - 11:59 AM

Hi I need some help in figuring out a water pump setup for my mobile rig. I currently am driving around in a town and country minivan but I've pulled all the seats out of the back to fit my generator, pressure washer, 125 gal water tank and all my detailing supplies. Vehicle was cheap and gets me good gas mileage too! I wish water would flow with just gravity but I have to use a water pump to get anything more than a trickle. My issue right now is that the Flojet Marpac washdown pump I have setup right now keeps overheating on me and shutting off after a few minutes of use, say like about 5-10 min max. Also, the pump just continuosly pumps so when Im not squeezing the trigger of my pressure washer the pressure is building up inside and this causes issues. Its currently powered off of my vans battery via a cigarette lighter power outlet on the vehicle so after Im done with a current spray of water Im constantly running back to my vehicle to unplug the unit so it doesnt overheat, build up pressure and spray water all over my inside and leave me with a dead battery.

I've looked into getting a pressure switch of some kind but from what I see they are all just for boats and am not sure if a float switch would work for what I need here. Is there some sort of pressure switch I can use for this rig or some sort of toggle switch I can use that will shut off the pump once I stop squeezing my pressure wand? Or should I abandon this setup and try to sell it and just go for a shallow well pump with the on demand shutoff water supply? I dont have a lot of money right now so I need to get this mobile water rig setup and working properly as thrifty as possible. Thanks for any helpful advice you can provide.

Heres a pic of the pump setup. When the unit is on, the clear plastic tubing tends to fatten up and will leak water at the seam where it connects to the out hose.
pump | Flickr - Photo Sharing!

#2 Ben@3D


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Posted 23 May 2011 - 12:10 PM

What you may want to try is an unloader that will flow water back into your water tank whenever you let go of the trigger. That way water is always circulating and your pump doesn't overhead. You can see some of the ones General Pump sells here: General Pump Unloader Valves For Pressure Washers

Also if you are going to be doing mobile full time, you may want to invest in a more powerful pressure washer that runs on gas.
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#3 the other pc

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Posted 23 May 2011 - 09:15 PM

Did you see my reply to your earlier post?

what water pump do I need for my electric 1800psi 1.6gpm PW?

#4 DetailKnight


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Posted 24 May 2011 - 04:55 AM

I would do away with the electric washer, and get a gas one!!! I gravity feed a 4 GPM cat pump with no problems what so ever. How long of a hose do you feed the electric washer with? The longer the hose, the better supply you will get... I use at least 50 ft of hose when gravity feeding. Try that first, before you do anything... might be a cheap fix!!!
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#5 sahrcar


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Posted 26 May 2011 - 09:19 PM

My pressure washer is a briggs and stratton and its doing pretty well for me when I can get enough water pressure to it for it to run. I like having the electric for its ease of use and portability since I transport my whole business inside of a town and country soccer mom van. Though lately I have been seeing some gas pressure washers about the same size. To Other PC and Ben, I do understand what yall are saying about having the relief valve but to get one of those will cost around $80 or so it seems. If Im spending that much more at this point it just might be best for me to go with some other kind of setup, sell what I got and just deal with a little financial loss. It was recommended to me though that I swap out my current electric and go with a karcher electric pressure washer. A manager at northern tool said that the karcher had a built in pump enabling the unit to draw water out of something small like a 5 gallon bucket and that the unit also had a built in cycle of some sorts that would perform the duties of a relief valve. I know Karcher has some higher end models that cost over $1k but Im wondering if the basic models more like in the $150-200 range will do that as well.

I did just have a really good week detailing wise and was able to obtain a few detailing gigs. Now that I have some available funds Im thinking about going ahead and just upgrading to one of the small sized gas pressure washers though I do also want to purchase a vx5000 steam cleaner. When Im not detailing I pick up odd jobs off of Craigslist and recently have been receiving inquiries in regards to if I can pressure wash houses- that I cant do with my electric in a timely fashion at least. I know at Sams Club they seem to have a decent 2700psi black max powered by a honda engine for only $300 or there is also a reconditioned Karcher G3050OH-R 3,000 PSI Gas Pressure Washer available on craigslist for $300 as well. I think both will fit inside my vehicle with my current setup. Im just kind of nervous about having a gas unit though as right now I am always taking my pressure washer out of my vehicle when I have to use it.

Would constantly moving a gas powered washer in and out of a vehicle be a bad thing for the engine? If I left it in the vehicle and ran it would it cause any issues to my interior.. ie potential to burn items nearby, inside smelling of fumes constantly? Currently how I have things positioned in my vehicle is that right behind the drivers and passengers seats are my plastic tote containers stacked up 2 deep. I then have my 125 gal water tank resting over the back wheels and then there is just enough room for my generator to sit in the back and for me to close the rear door hatch. My electric pressure washer sits right beside the generator. When I use my generator I remove it out of the vehicle since I don't want to burn the plastic tank behind it nor do I want to fill the van with fumes. Would these be valid worries with the gas pressure washer too? Also, just to be sure... I mentioned earlier that I was told the Karcher would pump and recycle the water in accordance with what I am needing. I'm assuming that since the gas pressure washers state they come with a self-priming brass pump (or at least the Black max does) that they will do this?

By the way, thank you all for your help thus far. Its really helped me analyze and understand things more and saved me from making further unnecessary expenditures.


#6 the other pc

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Posted 29 May 2011 - 06:38 AM


You shouldn't need to spend $80 on a relief valve.

If the problem is your washdown pump loading down, you don't need a valve that works to 1500 psi (i.e. a pw unloader). You only need one that works at the pressure of you washdown pump, which is probably less than 100 psi.

You can probably get something like that at a hardware or plumbing supply store for $20.

But like a said in my reply to your earlier post, you don't even need that. You can do it with almost any cheap adjustable valve (not a relief valve) or a hole drilled in a plug or even just some skinny tubing.


#7 Roger7811


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Posted 26 July 2011 - 02:12 PM

hey guys, im having a similiar problem with my mobile detailing rig currently im running a northstar pw powered by a honda motor
and cat pump 3.5gpm/4000psi connected to a 100 gallon tank. Right now my pump is cavitating i was told to use a short hose
from my tank to the water pump directly inline and i wouldnt need a water pump?? Also i was told i wouldnt need a water pump with this strong of a pw unit. Any kind of advice would be appreciated thanks guys.

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