# Liquid sprayer GPM question



## FourDiamond (Nov 23, 2011)

I'm in the design stage for a liquid spray system, and I have a question on GPM. Most systems I found on-line have a 5.5 horsepower honda engine rated at about 210 GPM per minute at about 50 psi. I would like to use a 12v system instead of a gas motor. What is the minimum GPM you can have and still have a operable system? The boom will be 8 foot wide with eight nozzles. I know there are a ton of variables. Just looking for a ball park number.


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## Kubota 8540 (Sep 25, 2009)

FourDiamond;2116784 said:


> I'm in the design stage for a liquid spray system, and I have a question on GPM. Most systems I found on-line have a 5.5 horsepower honda engine rated at about 210 GPM per minute at about 50 psi. I would like to use a 12v system instead of a gas motor. What is the minimum GPM you can have and still have a operable system? The boom will be 8 foot wide with eight nozzles. I know there are a ton of variables. Just looking for a ball park number.


8 nozzles at 1 gpm per nozzle = 8 gpm. But 12v pumps are not 100% efficient. Most are lucky to be 80% efficient. So at least 12 gpm to get some kind of low pressure capability.

You also need to be mindful that most 12 v pumps have a 10 minute on/10 minute off duty cycle unless you pay a few $$ more to get a continuous duty.


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## Brian Young (Aug 13, 2005)

We've been using a 12v Soterra pump (best on the market) and my advise...get the gas motor!!!!!!!!! I'm converting ours to gas motor. Our 12v is a 15gpm pump but it takes 25 minutes to fill our 300 gallon tank versus about 2 minutes with our gas motor/pump, doesn't have enough pressure to penetrate thicker hard pack and you need to drive about 5mph to put it down. Do yourself a favor and go with a gas motor. My only worry is the recoil freezing but I'm building a flip up motor cover for it to keep the snow off of it.


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## VS Innovation (Feb 9, 2016)

FourDiamond;2116784 said:


> I'm in the design stage for a liquid spray system, and I have a question on GPM. Most systems I found on-line have a 5.5 horsepower honda engine rated at about 210 GPM per minute at about 50 psi. I would like to use a 12v system instead of a gas motor. What is the minimum GPM you can have and still have a operable system? The boom will be 8 foot wide with eight nozzles. I know there are a ton of variables. Just looking for a ball park number.


You will find your biggest limitation on a 12 volt setup will be the speed that you can travel. For example, if you purchase a 12 volt pump capable 8 gallons per minute operating at 100 percent efficiency (not likely as Kubota said) and are trying to spray an 8 foot swath your speed can be calculated this way.

1 acre = 43,560 square feet
If you are spraying an 8 foot swath you need to travel 5,445 feet to cover one acre. (43,560/8)
The time needed to apply your desired application rate of 80 gallons an acre at 8 gallons per minute is 10 minutes.
In 10 minutes you need to travel 5,445 feet which gives you a speed of 6.1 mph running your pump at 100 percent of its capacity.

If your pump is running only 6 gallons per minute your speed is reduced to 4.6 mph. It will also take you over 13 minutes to spray one acre. This is where the duty cycle starts to become an issue.

As you can see the speeds are not overly impressive either. Even at 12 gallons per minute, your speed would be 9.3 mph if your pump is indeed putting out 12 gallons per minute.

The sprayers we use are very similar to the gas powered one you described. All of our sprayers are electronically (GPS) controlled meaning they control the flow rate to your boom depending on your speed and desired application rate. Even tho the pump is capable of pumping 210 gallons per minute, your flow rate at the boom is significantly less. Remember, these numbers are measured out of a 2 inch discharge hose pumping against very little head. Our sprayers are reduced down to one inch out of the pump to fit the electronic controls. An 8 foot boom with 16 1/4 inch jets can flow around 32 gpm at 40-50 psi. This is where your speed is increased and time spraying is greatly decreased.

At a flow rate of 32 gallons per minute you can now spray at speeds up to 24.75 mph before you begin to under apply your liquid. simply increasing the size of your tips to get more flow will in return increase the maximum speed you can travel. With a gas power pump, there is no draw on your batteries from an electric motor either. Running a plow, lights, and an electric pump can put a strain on your electrical system.

Also without electronic control (GPS), you must maintain the speed that your sprayer is calibrated for. In the case of the 8 gpm pump (100 percent efficient), 6.1 mph is the speed you MUST travel to obtain your rate of 80 gallons per acre. Any slower and you will be over applying, and any faster will result in under application which will yield poor melting results.

As stated in other threads I have posted to, our system allows us to accurately apply our liquid without the worry of over or under application. This saves us time and most importantly money. Our sprayers will control the flow rate as your speed changes and stop the flow when your vehicle stops.

These are just some of the many things to think about when building a sprayer. Flow rate is one of the most important of all considerations, and correctly calculating your flow rate and speed is the deciding factor in the performance of your sprayer.

I hope this helped! Let me know if you have any other questions. I would be glad to help you on your build!


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## Kubota 8540 (Sep 25, 2009)

Variables: If you are spraying an acre(s) 12 volt is unsuitable. If you are spraying small commercial or driveways, 4-5 mph is fine. If you are only spraying 1 or 2 accounts 12 volt might be fine.

How much are you going to spray?


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## FourDiamond (Nov 23, 2011)

At this point six or seven 1/2 acre lots. But the plan is to add a series of grocery stores with lots of various sizes from 1 acre to 3 acres


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## VS Innovation (Feb 9, 2016)

FourDiamond;2116919 said:


> At this point six or seven 1/2 acre lots. But the plan is to add a series of grocery stores with lots of various sizes from 1 acre to 3 acres


For those size accounts I would strongly recommend a gas engine pump. There will be much less headache and cheaper for you when the electric pumps decide to act up. Have you figured out a tank size? It sounds like you service around 3.5 acres with hopefully more to come! To service 3.5 acres at 80 - 100 gallons per acre (depending on conditions) you would need 280-350 gallons. A three hundred gallon tank would get you by if you plan on installing your setup in a lighter truck.

For reference, and you may already know this, but salt brine weighs alittle over 10 pounds per gallon. Knowing this helps you choose the right size for your truck without overloading it.


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## VS Innovation (Feb 9, 2016)

Brian Young;2116864 said:


> We've been using a 12v Soterra pump (best on the market) and my advise...get the gas motor!!!!!!!!! I'm converting ours to gas motor. Our 12v is a 15gpm pump but it takes 25 minutes to fill our 300 gallon tank versus about 2 minutes with our gas motor/pump, doesn't have enough pressure to penetrate thicker hard pack and you need to drive about 5mph to put it down. Do yourself a favor and go with a gas motor. My only worry is the recoil freezing but I'm building a flip up motor cover for it to keep the snow off of it.


Great post! I didn't even mention that we use our gas pumps to fill other trucks and our toolcat we use for sidewalks while we are out plowing. With the high flow rates of the gas pumps, we can quickly fill the 100 gallon sprayer in our toolcat. It is also very easy to unload your sprayer for daily driving.

I second everything that was said about the increased ability to cut through snow pack. Your brine will be much more effective if it can melt down to the pavement, exposing it for the sun to help warm vs melting from the top down.. You can achieve a higher flow rate and higher pressure with a gas pump, especially when using jet tips.


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## terrapro (Oct 21, 2006)

Gas is better then 12volt period and generally cheaper, 5.5hp engine/trash pump you can get for $300 new or so and will do everything you need.


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## Brian Young (Aug 13, 2005)

terrapro;2116981 said:


> Gas is better then 12volt period and generally cheaper, 5.5hp engine/trash pump you can get for $300 new or so and will do everything you need.


I'll second that, our Soterra 12v pump runs just over 800 bucks compared to the Honda 5.5hp motor and Banjo pump at 600 bucks. Only reason we have this electric pump is the guy had this system returned for whatever reason and it had this electric pump with it when we bought it and couldn't pass up the price of it. Until the last couple season it was pretty much a back up if we went through another salt shortage. Now we use it in one of our trucks now but only use it on 5 smaller accounts using about 450 gallons each round. Do yourself a favor and just put a engine/pump combo together. Like Terrapro said you can buy a briggs engine/pump combo from TSC but for a couple hundred more you'd be into the Honda engine with pump. Go to Dultmier on line, they have everything you will ever need to build your unit. I could go on for pages of what we've tried to increase our out put of liquid but in short gas is the way to go.


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## terrapro (Oct 21, 2006)

A 12volt pump is basically a low powered shut off valve that restricts flow and doesn't work very well. IMO gravity feed with an electric valve is better than a 12volt pump and a hell of a lot cheaper


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## VS Innovation (Feb 9, 2016)

terrapro;2117022 said:


> A 12volt pump is basically a low powered shut off valve that restricts flow and doesn't work very well. IMO gravity feed with an electric valve is better than a 12volt pump and a hell of a lot cheaper


There is no doubt that gravity feed is a very reliable way of spraying. I have never seen the lack of the presence of gravity yet! We have been forced to use a gravity feed system only a few times and it did work, however there is a big downside to gravity. When your tank is full, you will have a decent flow rate. As your tank begins to empty, there is less force behind the liquid. This drastically reduces your flow rate to you boom (even when plumbed with 2 inch parts). Your flow rate is constantly being reduced as your tank level drops, and monitoring the rate at all levels is nearly impossible.

We have tried several different electronic valves. We have found the TeeJet brand to be the most reliable. Make sure you keep your wiring free of corrosion. These units do not handle voltage drop well, and tend to not function properly with a corroded connection.

Again it all depends on the type of spraying you are planning on doing. If you plan on a gravity feed system, plan on a boom suitable for this application.


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## FourDiamond (Nov 23, 2011)

Thanks for the replies. Based on the answers gas is the way to go. The tank size at this point looks to be 350 gallons, and it would go a f550 so weight won't be an issue. I'll keep everyone posted as this thing gets off the ground in the next month or so. I'm also sure I'll have more questions as I move along.


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## Hysert (Dec 16, 2009)

V'S... I would assume your large 2700gal has baffling inside?? With the -20c temps we have had over the past few days, I'm starting to look back into pre treating at the spinner!!! I'm not interest in going full liquid!!! Gonna start on something for next year?? I would like to run the prewet system on a 12V and wire it to m upfitter switch that I have the vibrator connect to, my plan is only to use it when it's really cold, and be able to switch from vib to liquid pump, just bc we still use sand here and there on gravel lots.. BTW that liquid truck is real nice


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## FourDiamond (Nov 23, 2011)

Not to hijack the thread. But does anyone add dye to the brine solution as a marker. I've been around ag sprayers my whole life and we always used foam markers, but with deicer dye in the solution would work the same way. Any thoughts.


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## VS Innovation (Feb 9, 2016)

Hysert;2117220 said:


> V'S... I would assume your large 2700gal has baffling inside?? With the -20c temps we have had over the past few days, I'm starting to look back into pre treating at the spinner!!! I'm not interest in going full liquid!!! Gonna start on something for next year?? I would like to run the prewet system on a 12V and wire it to m upfitter switch that I have the vibrator connect to, my plan is only to use it when it's really cold, and be able to switch from vib to liquid pump, just bc we still use sand here and there on gravel lots.. BTW that liquid truck is real nice


Thanks for complement on our truck! We really enjoyed the build! Our 2700 gallon sprayer has baffles molded into the tank. It uses the structure of the legs to help slow down the liquid movement. The tank is still completely open inside. I just sprayed a 1/2 inch snowfall with it this morning. Even when half full, the truck barely notices the liquid movement. You can only feel a gentle sway when accelerating from a stop, other than that, the performance of the truck has not been affected.

We toyed with the idea of prewetting salt using a spreader setup. There is some added benefit of utilizing the best of both practices! We do deal with very cold temperatures here, and have even found ourselves spraying in -20 degree F temperatures. We just add more calcium chloride when the temperatures get this low.

Good luck on your build! I'd be interested in hearing your progress!


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## VS Innovation (Feb 9, 2016)

FourDiamond;2117311 said:


> Not to hijack the thread. But does anyone add dye to the brine solution as a marker. I've been around ag sprayers my whole life and we always used foam markers, but with deicer dye in the solution would work the same way. Any thoughts.


In most cases when spraying, it is very easy to see where you have sprayed and where you haven't. The brine acts very quickly, and bare pavement is exposed in less than a minute. The calcium chloride we use contains a beet juice additive that helps that brine stick to the pavement. It lowers the freezing point of our mix, and also contains corrosion inhibitors to help slow down one our industries biggest enemies, rust. The beet juice gives the calcium chloride a dark red color, which does act as a dye. So to answer your question, no we do not run any kind of dye and I am honestly not familiar with anything designed for this purpose, however, the mix of products we use are very visible when sprayed.


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## terrapro (Oct 21, 2006)

Yeah it would be difficult to not tell where you have sprayed with liquid plus customers probably don't want a dye tracked around their businesses


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