Question on electric diaphram pumps

I have a 25 gallon sprayer that came with a Flojet 12v electric pump. This model pump is rated at 1.8gpm and 70 lbs of pressure and is an on demand type pump. I have a gun type nozzle on it that shoots a pretty good stream, but it wouldn't quite reach the tops of large fruit trees. The pump has seriously lost pressure and has a hard time priming itself. I have ruled out obstructions in the system, so I assume the pump is just wearing out. Now, would I get greater spraying distance by going to, say, a 100 pound of pressure pump with the same gpm rating or would I do better with maybe a 60 lb pump with a higher gpm rating? I'll have to order whatever I get so I want to order the right thing.

[Old Vet]

It all depends on what spray gun you are useing. If the spray gun is big enough to handel the higher presure and the gpm is larger than yu have then you will have to get a larger pump to acomotate the gun. If you go with the smaller pump and can reach the level that you are hoping for then all you have is a pump that is worn out and willnot produce the presure that you need. All spray nozels have the gpm rating on them you can not go higher than that trough them without increasing the size of the hole that they spray through.

[jacksun65]

why not rebuild the pump you have they are the same ones used in campers.

Thanks. The gun is rated for up to 250 lb of pressure. I was trying to figure the best way to force more pressure through it, either by buying a higher pressure pump or buying one with greater GPM. I am more concerned with distance than volume. I really like the electric pumps if I can get the pressure right. They are much more convenient than a roller pump with a gas engine and belt to mess with.

Originally Posted by jacksun65

why not rebuild the pump you have they are the same ones used in campers.

I considered that, but I would like to get greater pressure out of the system if I can. I figure if I just tell my wife it is broke, she won't object to me buying a new one.

[Fire-Man]

Originally Posted by poppy

I have a 25 gallon sprayer that came with a Flojet 12v electric pump. This model pump is rated at 1.8gpm and 70 lbs of pressure and is an on demand type pump. I have a gun type nozzle on it that shoots a pretty good stream, but it wouldn't quite reach the tops of large fruit trees. The pump has seriously lost pressure and has a hard time priming itself. I have ruled out obstructions in the system, so I assume the pump is just wearing out. Now, would I get greater spraying distance by going to, say, a 100 pound of pressure pump with the same gpm rating or would I do better with maybe a 60 lb pump with a higher gpm rating? I'll have to order whatever I get so I want to order the right thing.

I don't know alot about this---But I feel if you have 1.8gpm going through a hole at say 30psi or if you tried to put 3gpm through the same hole at the same pressure you will get more reach----So I would go for more GPM. I have ordered new diaphram to replace the one in my pump---Called the manufactor---they gave me my closest dealer that would have the part---called and got it shipped to me. I have also taken the pump apart and clean the diaphram and housing and have found trash in it---put it back to working good--with a just a cleaning. Good Luck!! Randy

[fordy]

Originally Posted by poppy

I considered that, but I would like to get greater pressure out of the system if I can. I figure if I just tell my wife it is broke, she won't object to me buying a new one.

..........These types of pumps are also used in RV's . You can buy a rebuild kit online . The plastic housing maybe cracked and loosing pressure so I'd check into a kit before buying a complete motor as they usually last along time . fordy...

[agmantoo]

The inlet checkvalve is not totally seating. That is why you have low pressure and and difficulty priming.

Originally Posted by agmantoo

The inlet checkvalve is not totally seating. That is why you have low pressure and and difficulty priming.

That sounds about right. I did pull it off today and the valve doesn't look worn at all and the seat is clean. Not sure why it isn't seating, but I will check further.

[agmantoo]

Does the pump use a "plastic" ball for a checkvalve? If so, the ball could have disorted and be out of round.

[artificer]

I guess I'm a bit confused. The pump is wearing/worn out, but was it ever able to hit the top of the trees? (re-reading the post makes me think it never reached the tops???)

If it never could reach the top of the trees, you need more pressure and a new pump.

If you haven't tried it until recently, with the questionable pump, then you need to see what pressure you need to reach the tops of the trees. Can you beg/borrow/steal a pump with higher pressure to test your gun? What pressure does it need to get the reach you need?

The pump will max out at 70psi with no (or little) flow, but will have much less pressure at full rated flow rate.

One thing to remember is that flow rate is determined by the hole/orifice size and the pressure. It doesn't matter what the gpm of the pump is, as long as it can keep up with the maximum theoretical flow rate. The only way to increase the flow rate is to increase the pressure. HOWEVER... if your pump isn't providing the necessary flow/gpm for the nozzle in the gun, you haven't reached the maximum flow the nozzle can handle. A pressure gage in the system would be very helpful to see what you're operating pressure is at.

If the pressure is lower than the max the pump puts out, you need a higher gpm pump. If its at the max pressure, but you don't have the reach, you need a higher pressure pump.

Can you hook the gun up to a garden hose and see what the reach is that way? That will test the flow rate, anyway.

What is the oriface size? If you know that, you can make an educated guess at what you need to max out your flow rate.

Michael