Gasoline Powered Water Pump

It may be a dewatering pump only designed to lift the water out of the trench, therefore not high pressure.

But it also may have to be primed properly (no air in the system) before the pressure is available.

More detail please. A picture might help us to identify the type.

thanx for the feedback. it was well primed. here is a link to the product. much obliged. steve http://www.harborfreight.com/portable-water-pump-with-65-hp-gas-engine-and-3-inch-inlet-outlet-95976.html

use pressure regulator !

http://www.harborfreight.com/portable-water-pump-with-65-hp-gas-engine-and-3-inch-inlet-outlet-95976.html this is a link to the pump. how and where would i install the regulator? much obliged. steve

The hose bib is for priming

use this connection as an air bleed line

install a TEE on the outlet, install a hose bib facing down

put a gate or ball valve on the other connection, with a hose going back to source, throttle the valve back to around 1/2.

this will give your pressure washer a constant supply

Kramarat is right about pressure washers, many have chevron seals on the pistons & consequently don't suck well

hmmm, interesting. this may not be ideal but still doable. i currently have a 3" plug in the cam lock where the outlet hose would normally go. so would i tap the aluminum plug to install this tee, one side going to a hose bib and the other going back in to the primer? is that it? steve

I'm wondering myself about it. I thought some one might have been posting from thrid world country where even people use carosine powered generators but then it is only gasoline (gas. in usa). Are things any different? Heheheheheh.....

just make up a camlock TEE with a valve & a hose bib

of course that's like $50 worth of parts in polycarbonate [black plastic] & iron

reducing down to 1 1/2" or 2" at the outlet will save some money on fittings & hose

these pumps don't deadhead very well

anyway you can get some flow going will probably work

you might even get away with 2 hose outlets, one running wide open, one hooked to the pressure washer. How I would proceed would depend on what kind of parts I had laying around & how quick I needed it working

At 263 gpm x 82 ' it should do some cleaning (barely).

Some self priming pumps however expel the prime without enough back pressure at the discharge side.

fit a 3" valve on there and open gradually.

What was the suction hight and hose and fittings? any leaks.

Maybe replacing the pump would be better.

This is a self-priming dewatering pump, designed for shifting reasonable volumes of water at relatively low pressure. It is not designed for pressure washing. To give you some idea, this pump will give you about 35psi, whereas pressure washers operate at about 1500-3000psi. Furthermore, if you are operating the pump at max pressure, it would be operating at the top of the performance curve, which could be humped, resulting in hunting between two duty points. You might need to use a larger diameter or shorter hose (or nozzle) It will give you more flow and slightly less pressure, but it will be steady.

I think your pump is probably experiencing cavitation/back pressure due to large volume in and small volume out. Plug the garden hose outlet, run the 3" outlet into a holding tank with a garden hose outlet fitted to the bottom and use gravity to feed your pressure washer. This should work fine. If possible place pressure washer downhill from storage tank. Hopefully you haven't already blown the seals on your pump.

A rain catcher drum may fit the bill and they are already fitted with hose attachment.

Remember, this is a self-priming pump, designed to prime and pump with up to 25' of suction lift. So I wouldn't change anything on the suction side, apart from making sure the suction hose is re-inforced and is not collapsing. You would only get cavitation or suction problems if the suction hose was much less than 3" or lift more than 25'. Raising the suction tank will at best maybe give you a couple more psi on the discharge.

Hendrik mentions that at 263gpm x 82' it would barely clean, but these are maximum figures at different points on the performance curve, and at 82' (about 35psi) it could actually be giving much less than 50gpm.

I'm confused now. I just looked at the pump and manual. http://www.harborfreight.com/portable-water-pump-with-65-hp-gas-engine-and-3-inch-inlet-outlet-95976.html

I see nothing about using a garden hose connection as an outlet. 3" in, 3" out. This pump is designed to move 263 gallons per minute, unobstructed. A pressure washer uses maybe 4-5 gallons a minute. This will never work. If your holding tank is below ground, like I said, you need an above ground tank and gravity feed the pressure washer. If the holding tank is above ground, eliminate pump and go straight gravity feed. Other than that, you need to get a smaller pump, with a bypass going back to the tank, that is suited to the inlet pressure and volume of the pressure washer.

Take a look at these transfer pumps, they are designed for, among other things, feedwater supply to a pressure washer.

http://www.ultimatewasher.com/transfer-pumps.htm

I must apologize, I am guilty of one of the things I most hate to see, misreading of the OP. I assumed this pump was being used as a pressure washer, not for feeding to a pressure washer.

Either way, the problem with this pump is the same. Garden hose is far too small in diameter to be used for the discharge of a 3" pump, and is throttling it back too much (virtually running at 'closed-valve'). However, if you are feeding directly into the pressure washer then just changing to larger diameter discharge hose will not be enough, you would have to feed into a seperate suction tank for the pressure washer.

The easiest solution is probably exactly what you suggest, a bypass from the outlet either to the inlet or back to the suction tank. This will relieve the throttling of the discharge and allow more flow through the pump, so it should run better. Garden hose should give enough flowrate to feed the pressure washer.

Still confused here. Even if you are able to bypass most of the water, you will be using an oversized pump to circulate 263 GPM, to feed a pressure washer which requires about 5 GPM. 258 GPM just going round and round. At the very least, even if you succeed, you are going to be burning a lot of fuel to do some pressure washing.

Yes, you are quite right, I think your figure of 4-5gpm for the pressure washer is about right, so there would be a lot of wastage. The only solutions are:

a) Buy a much smaller pump to feed the pressure washer.

b) Run the existing pump for a short time only to feed a header tank that feeds the pressure washer.

c) Accept the wastage and use a lot more fuel.

I would go with option b, since he already has the pump. It's hard to tell from the pictures, but I'm almost positive that the hose attachment that he is using attempting to use for full time discharge is simply a way to attach a garden hose to the primer outlet to avoid getting the engine wet.

How about one of these to supply that pressure washer?????

Can be bought at Granger - Mfr. Model# 4CG57

EDIT - My bad, this is not gas powered and would have to be plugged in to 120V.

EDIT EDIT - Buy this pump and a cheap gas generator - problem solved.

the same basic pump can be coupled to a small lawn mower engine without much difficulty. You would still want to recirculate back to the supply tank a portion of the flow, and perhaps you could benefit from a demand (splitter) valve that would maintain supply pressure to the suction of the pressure washer. A 1" water pressure regulator would probably be large enough at act as the splitter valve. I leave it to you to understand how to install it.

Whenever I am in this situation I try to use a smaller "recycle hose" back to the water source

I have witnessed a similar situation when they were drafting from a dry hydrant to fill tankers. They set up an unmanned deluge gun to send water back into the pond. At the time I thought this was to keep the pump from overheating from churning when the water was shut off for several minutes between tankers.

Excellent comments, old salt, just a couple of points:

'the pump is designed to pump water and not air' - remember we are dealing with a self-priming pump here, so it is designed to handle air and mixed-phase. However, priming could also be impeded by the small bore and resultant back-pressure with the garden hose. Besides which, it might not be a good idea to be pumping air-laden water into the pressure washer. If a recirc line were used, it should return to tank not to suction, and it should be used for pump priming before feed is tapped off through the garden hose to the pressure washer.

You are quite correct that the pump is not operating in an efficient range. In fact it is operating to the far left extremity of the performance curve in the 'danger-zone'. It is very difficult to get stable flow/pressure in this zone (as I mentioned before), but it is also where radial loads on the shaft are highest, and it can affect bearing, seal and pump life. But a recirc line should solve this problem.

Conjecture: Do you know the internal plumbing of the pump? Could the garden hose nipple be the outlet from a relief valve? Thus it would flow only when the internal pressure opened the relief valve. If this is the case, cap the 3" outlet and adapt to a garden hose nipple. However, you would still have the large difference between the capacity and the outlet volume.

It has all been said.

The pump that you have will NOT do the job that you desire. Unless you suck on a 3" Pipe and push on 3" pipe.

All the wishing, kicking and farnarkling, will not change one thing.

You require a "Pressure" pump., that is DESIGNED to do that, which you wish.

Mark N.

wow that is a lot of good information. yes the gentlemen that suggested the garden hose nipple on the pump was for priming, he is correct. i am doing some home construction in africa and wanted something that could draw from a body of water if i came up short on water for cement. i was also thinking that i could use it to supply my pressure washer to hose down equipment at the end of the day. i can see now that it simply wont do. although i should be able to fill an elevated tank which would than apparantly be able to supply enough head pressure to the pressure washer (at least some in the group seems to think so) not being a water engineer i took it to a store specializing in hoses and couplings and the guy set it up for me this way saying it would work (unless we had a miscommunication) does anyone know how high the tank should be to supply adequate gravity feed) thanx for all the feedback. steve

The tank doesn't have to be very high at all, in fact level with the pressure washer would be OK. Pressure washers usually use triplex piston pumps to achieve the high pressure, so their suction capability is usually pretty good. In fact, I have even seen them used for drawing water out of places, and I'm sure somebody does a kit for this purpose. Furthermore, the flowrate is very low, so there should not be any suction problems leading to cavitation, as long as you don't use a ridiculously small or long suction hose.

does anyone know how high the tank should be to supply adequate gravity feed

It doesn't matter, as long as it's a few feet above the highest point you'll be using the pressure washer.

I wouldn't recommend using your pressure washer to draw water, this will put a strain on the plungers that they are not designed for, they are made to push water. A gravity feed system using a tank should work. Here is an adequate checklist for you to review.

http://www.ultimatewasher.com/pressure-washer-tanks.htm

The plungers or pistons in these pumps are designed to handle 1500-3000psi discharge pressures, so I would be surprised if they were delicate enough to be troubled by 5-10psi on the suction side. Anyway, when you are looking at pump suction conditions (eg doing NPSH calcs) you are considering absolute pressures, not gauge pressures, since this is effectively what the pump suction 'sees'. So the Net Inlet Pressure can be positive even if the liquid level is below the pump inlet.

Many pressure pump manufacturers/suppliers state quite clearly that their pumps are self-priming and can draw from wells or underground tanks. They usually quote suction-lift capabilities in the range of 3-7ft.

However, there seems to be a lot of variation, and some pressure pumps clearly don't prime as well as others (if at all), so ultimately it is best to look at the pump specs and check the recommendations of the manufacturer/supplier of the pump. Gravity feed might be ideal, but it should not necessarily be considered mandatory.

Many pressure pump manufacturers/suppliers state quite clearly that their pumps are self-priming and can draw from wells or underground tanks. They usually quote suction-lift capabilities in the range of 3-7ft.

Pumps, yes. Not pressure washers. Pressure washers are not self priming and are not designed to pull water. Every pressure washer I've seen must be purged of air before starting, not just the pump, but all the way out to the pressure tip. I'm not trying to argue, but I've got to stand firm on this one and say that using a pressure washer to draw water will greatly reduce its life expectancy.

I meant to say pressure washer, but anyway a pressure washer is effectively a triplex plunger/piston pump on a motor or engine with a bit of plumbing, and sometimes a fancy case.

I'm a bit pushed for time at the moment, but I'll put something together this evening to back this up.

If you can show me something that says it's alright to dry start a pressure washer and use the inlet to pull water uphill, I will stand humbly corrected.

Well, there does seem to be a huge amount of variation, ranging from infinite dry-running to "never run dry or feed from a water butt" and everything in between. All the more reason to check manufacturers/suppliers specs & recommendations. The triplex piston/plunger pump is a positive displacement with very close clearances which enable it to reach such high discharge pressures. As such, its' (primed) suction capabilities should be as good as any other pump type, and within the usual constraints (friction losses, vapour pressure, etc) could theoretically lift up to about 30ft.

The following are some sites that mention dry-running, priming, dewatering, etc:

Kranzle. Run Dry

Nilfisk suction kit

Nilfisk. Draw water from well.

Well sure enough! I wasn't aware that such washers existed. I stand corrected. I learn something new every day.

That said, the Nilfisk suction kit actually uses the outlet at the pressure tip to create a suction, so that's out for this application. Secondly, these look like fairly specialized units that are specifically designed to draw standing water. I think it's unlikely that the OP, who buys cheapo stuff from Harbor Freight, has possesion of one of these units, but has an off the shelf, standard pressure washer.

I appreciate the information, (I wish I had one of those). I think we can agree that the OP needs to consult the owners manual for his pressure washer, and go with what it says for inlet pressure.

Kaercher is the biggest name in pressure washers here in Europe, so their units would be pretty standard and 'off-the-shelf'.

But you're right, we can agree the OP needs to consult the manual/manufacturer. In fact, I didn't realize their could be such variation in recommended inlet conditions, so this could also change the options in Post #12 . If the pressure washer requires, say, 2 bar inlet pressure then a header tank might need to be located at too impractical a height, and the existing water pump also might not provide enough pressure by the time it reaches the pressure washer.

Very gracious of you.

Your original assertion is, of course, correct for the vast majority of pressure washers. Here's the relevant passage from the manual for a Northern Equipment pressure washer, this one about as typical as you can get.

• Never use a reservoir tank as a water source. Drawing water out of a tank may cause pump cavitation and damage to your pump. This pressure washer is designed for a pressurized water source such as a city water faucet. However, the water source pressure must not exceed 115 psi (8 bar).

There are guys around here that do mobile car washing that use use holding tanks on trailers, but I think even those use a small 12 volt feed motor to the washer. I've never seen anything in the US advertised to draw water from a standing source. I wonder why?

I have a 25 year old pressure washer and the pump actually has outlasted the 13 hp Honda engine, which I rebuilt last summer. An interesting side note, the rebuild kit for that engine was $60 and included pistons, rings, valves, seals......everything, and was very easy to do. Apparently too easy, because Honda, as well as a lot of other companies, no longer will allow the public, access to their factory manuals, only dealers. Fortunately, I got a dealer to print me up a manual back in the days before the internet got going strong, and these rules were implemented.

I agree. Some pressure washers are equipped with low inlet pressure shutoffs for this reason. They can cavitate with low inlet pressure. The pump internals are built with the intention of high inlet pressure, meaning small internal passages that can cause high pressure drops. The OP should read the manual for the washer, but ordinarily there will be a minimum inlet pressure spec.

30 psi = 69.2 ft; 10 psi = 23.1 ft ; 5 psi = 11.5 ft.; The suction side maximum lift is 25 ft. This "Lift" will have the biggest effect on flow from the pump. (keep it short as possible) And Good Luck

I agree with Holzfeller. It's a nice pump for moving large volumes of water. It isn't designed to give high pressure. Nice pump, wrong application.

If you are using a 1" or 5/8" garden hose for the suction line in the tank of water, You are starving the Suction of the pump. The suction line needs to be 3" Non-Colapsable hose.

Does this pump have (2) Two Out lets? 1-3" & 1- Garden hose connection?

The smaller the hoses you use the more restructions you are puting on the pump.

Those pumps are designed for using 3" Suction Hose and 3" Discharge hose.

You can reduce the discharge hose size but the friction losses win the smaller hose will reduce your out let flow and pressure.

I think you need to save time and money. Rather then Rube Goldberg your pump with the suggestions of modification why not go back to Harbor Freight and get a cheapo high pressure washer?

Did you actually read the original post?

captsteve is using this pump to supply water to a gas powered pressure washer [most of which require 20 psi or so], he doesn't really say where the water pump in question is getting it's supply, but it is probably a water tank or truck with little or no pressure, which would be common on a construction site, the water being used mostly for dust suppression

Yes I did actually read the post, did you?

"I immersed the inlet hose in a tank of water and inserted a plug in the outlet." Unless I read that wrong he says he PLUGGED the outlet.

I looked on the manual and I see no tap for a "garden hose". It's 3 inches in, 3 inches out. Perhaps the link that was provided was the wrong one? In the manual it calls out braided line only or some type of non collapsible hose. The whole thing sounds really Mickey Mouse to me. The manual also states its designed for moving large volumes of water like swimming pools and holding ponds. I guess I missed the part about plugging the discharge outlet and using a garden hose to feed a pressure washer. I did however see the part about voiding the warranty for any alterations or uses other than applications for what it was designed for.

He already has a cheapo pressure washer, and a trash pump. He doesn't need another pressure washer.

Here's what he wrote:

It also has a standard garden hose nipple which I had hoped I could use to supply a gasoline pressure washer to clean construction equipment in the field.

You are sucking air in the drawline somwhere.

hi guys, i am in the middle of mozambique so no graingers and no harbor freights. i failed to test this application stateside before leaving. when i tested it over here i dropped the reinforced inlet hose into a concrete tank that is a ground level and about 2 meters deep. it draws fine. than i tried to use it to supply my pressure washer which has a standard garden hose inlet. i removed the 3" inch outlet hose and inserted a plug. opened up the primer inlet which has a hose bib in it and tried to supply the pressure washer from that. it is true it is not meant to be an outlet. i should have intuitively known that it would be too much in and not enough out but didnt think about it carefully. it looks like my best option is to use the water pump to fill an elevated tank and than pressure feed the washer. thanx for all the thoughts and suggestions. at least i know that nothing is actually defective (other than me that is) regards steve

Thanks for the update Steve. Several people have pointed out that you need to check the input spec. of the pressure washer before deciding on the height of the reservoir tank, so, it looks as though my reply at #22 above was not correct.

Hey Steve,

Parts may not be available there. But given what you already have, if you can find a 3" Y fitting to go on your 3" outlet, combined with a reducer on the Y to fit a garden hose, you should be fine. Here is a picture. Your garden hose fitting would go on top, the rest would be recirculated back to the holding tank. I'm building on Garthh's idea. I'm sure the feed pressure would be adequate, and you won't burn up either pump. You may want to submerge the discharge end of the outlet in the holding tank water, creating just a tad of back pressure.

PS- To save yourself having to modify the main water pump discharge or discharge hose end coming off pump outlet, you could just cut your discharge hose and install the Y inline with hose clamps.

I think the problem may be necking down the pump outlet doesn't let it prime properly and air is retained.

What you need is a 'T' on the outlet with a cock you can open [to return the flow to the tank, purge all air via a full flow through the pump] at start up - then shut the cock partly, or fully, to supply pressure to the washer.

As washers use very little water, it's probably best to leave the bypass cock open a bit to stop the pump over heating.

BTW, my Stihl washer will draw from a meter - they say. But is generally quite happy to run from an above ground tank - say min head 6 ft.

The pump has a primer/air purge valve located on top that he is currently attempting to use as the discharge. I think all he has to do is return the pump to it's original configuration..........remove the plug on 3" discharge, hook up 3" discharge hose with Y fitting installed inline, and use the purge valve for what it was intended for, to prime and bleed off air. I could be wrong.

If I'm getting it's like a 'fire fighter'

Shutting the outlet and using the air bleed will get you to some flow - but then - you need a good flow to get all the air out - then you can shut down the outlet to a trickle or whatever.

He could just use a reducer and the small hose [in the proper port] as a recirculation, but it will take a longer time. Then when he plugs it in to the washer, it leaves the over heating as an issue without an adequate cooling recirculation.

I'm thinking that the pump is designed to move large volumes of water from one place to another. The problem with any kind of reducer, even if it's used to recirculate, is that it's going to create back pressure that the pump isn't designed to handle. I think the Y fitting would allow for the free flow of water, (which is what the main pump wants), while at the same time, supplying the pressure washer with inlet water at positive pressure, which is what it wants. Everything should be happy.

The pressure can't exceed the maximum head - and the casing and seals are designed to withstand that.

Once the air is purged, it can just idle.

T, Y who cares

Exactly, who cares. I do think these pumps are either running full bore though, or off, there usually isn't an in between, (idle).

Although, considering the OP is from the US, and he's over there in the middle of Africa, he's probably doing something worthwhile. I'd like to see him come up with something that works. I guess I do care.

I'm not sure what you both mean when you say the pump will 'idle'. Once the air is purged, and it is primed, the pump will pump. And the flowrate could be anywhere from 0gpm at closed-valve to 263gpm at (or near) End Of Curve, or anywhere inbetween, depending entirely on the system head (or call it back-pressure) that is presented to the pump.

Around here many of the contractors and private pressure washing guys use a simple and cheap 12 volt pump to supply the few PSI of pressure that some pressure washers require to operate properly.

A $30 12 volt DC pump and a good garden tractor battery will solve your problems plus wash all day long on one charge!

That was mentioned, I don't think he can just run down to the store in Mozambique and get one.

My tuppence worth is similar to many posts above.

The top plug is for adding some water before starting the pump, so air expelled will not return, as the flap valve in the inlet is lubricated.

The bottom plug is for draining the pump for storage - especially in cold climates where damage will occur if the residual water freezes.

Use a rigid 3" inlet hose from the supply.

Put a 3" T or Y on the outlet, then reduce one outlet to 2 1/2" (firehose) and discharge back to the supply if there is no other use for the water.

The second outlet can then be reduced to garden hose diameter and give a reasonable pressure without fear of destroying the pump through cavitation or the garden hose by over pressurising.

Nice summary

Thanks! You can't tell I use them at work?

Not a bad summary, but a few key points worth noting:

1) The top plug is indeed for priming the pump. Most self-priming centrifugal pumps need to be primed first time, after which they retain some fluid in the pump and can prime themselves.

2) It is very important that the OP should check with the manufacturer/supplier the required inlet conditions for the pressure washer (having seen how they can vary). If they require 2bar, for example, then the cheapo water pump might struggle to supply this, especially through a long length of garden hose.

3) It is not enough just to run the recirc line through 2 1/2" hose. At this size and, say, 250gpm, even 10-20ft of hose will only give a few psi in friction losses, so the TDH will only be a few feet. The pump will effectively be operating close to End Of Curve, generating very little pressure, and putting all the flow (or virtually all) through the recirc line. There will not be enough pressure to put anything more than a trickle (if that) through the garden hose. You could calculate an ideal size/length for the recirc line, which would probably come out somewhere between ¾-1" ID, but it would be easiest to put a control valve on this line so that it can be throttled back to achieve max pressure.

4) You would still need to be careful about throttling back too much, running too close to 'closed-valve' and overheating the pump.

5) You would still need to be careful about the garden hose length and pressure washer inlet requirements, bearing in mind that 100' of ½" hose at 5gpm will give a head loss of about 75' (32.5psi).

6) Discharge restriction/pressure cannot in itself cause cavitation, which is a suction issue. The only instance it can have an effect is when the pump is run continuously at closed valve, in which case energy is still being put into the pump, but since no fluid is going anywhere (apart from recirculating inside the pump) most of this goes into the fluid in the form of heat. As the fluid heats up and approaches its' vapour pressure cavitation may ensue.

7) This pump cannot supply more than about 35.5psi (on water) so it is unlikely to damage garden hose, bearing in mind most domestic supplies are 30-75psi.

Yes he was remiss in not including #50