# On Booster Pumps



## mwemaxxowner (May 30, 2020)

I'm currently sort of in the R & D stage of wanting to build an irrigation system at my house. At this point I'm just researching and learning, and dabbling with designing it on paper. I've read through Stryker's tutorial several times, and spent even more time on certain topics reviewing the material further.

The purpose of this post is how a booster pump may benefit me. I currently have a 3/4 irrigation meter, at which I see 32 psi static pressure and I get 7.5 gpm with a bucket test right at the meter.

The other meter I have servicing my house also gives me 32 psi and 7.5 gpm.

I've been through the pumps section of the tutorial quite a few times. I think I understand most of it, I understand the pump curves and how to decipher pump ratings and compare that to your goals.

I would want to select a pump that gives approximately a 20 psi boost, but what I'm not totally sure about is how that will, or won't, affect my flow. The irrigation tutorial, almost from beginning to end, seems to assume that those with water from a municipality have ample flow, and talks more about not using too much flow (to keep speeds within the pipe at safe limits) than it talks about what to do if you don't have enough flow.

I've already run 2" main line from the irrigation meter, and plan to continue to do so as I work on plumbing it to the irrigation valves. I want to use 1" for my laterals, or if it will benefit me I'm fine using 1.25 or even 1.5.

If I select a pump that is rated at, we'll say 20 psi boost and 20 gpm, will it be able to bump my gpm up? Will it boost the pressure but not boost the flow? Will it perhaps even reduce the flow?

I have a 3/4 meter, and I think 3/4 pipe can safely flow up to about 20 gpm. So let's say 20 gpm is what 3/4 pipe can reasonably flow, would a pump be able to pull that much through the meter from the supply pipes?

Next door there is an irrigation system also with only about 32 psi, but he has 10 gpm, and his system seems to perform well.

I'm not sure if I want to jump through many hoops to only gain 2.5 gpm though. That only really allows me am average of one extra head per zone. It doesn't reduce the amount not pipe or plumbing work significantly, and I'm not sure it would make a big difference in the amount of time I have to run the system either.

So, I'm thinking, if I can't use a booster pump and get the flow to, perhaps, 15 gpm, I'm not sure it's a worthwhile endeavor.

If this is plausible, I'm guessing I certainly don't need the pump to be oversized. I guess if it's trying to pull much more flow than it's going to be able to, that would be bad for the pump and it may cavitate also?

I've been playing around calculating friction losses and whatnot on paper. It seems like with the right nozzles (that do coincidence with Stryker's recommendation for min flow rate nozzles) I can make this work with 20' spacing and 3 heads per zone, even with no pump. I think. So if it seems like I could probably make it work with no pump, I'm thinking I don't need huge improvements and a super duper really capable pump. If I could just boost my design pressure (and available pressure) to 45-50 psi, and manage 15-20 gpm, I'd be good to go.

Right now, I'm using 2 orbit 4 valve programmable timers, 3/4 water hose, and melnor impact sprinklers. I'm able to hide 90 percent of my hoses in my shrub beds and this has worked pretty well this summer to establish my sod and keep it doing well. I just am not able to hide ALL of my hoses and would like to be able to get away from hoses.


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## mwemaxxowner (May 30, 2020)

After spending a good bit of time on the web for this last night, I believe it's may increase my flow a small amount, but not much. And not to count on it.


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## mwemaxxowner (May 30, 2020)

One final update on this post for anyone who might find it while searching out the same thing.

I've consulted with a few pump distributors/manufacturers and determined that no, in my situation a booster pump will not boost flow (gpm).

The tutorial says a booster pump may increase flow, and reminds us in that portion that along with more pressure comes more flow. That, I believe, is talking about situations where you have more gpm available from your water source than you are using with your heads. I think it's reminding us that, if we boost the pressure, and more flow is available from the meter, that you're going to get more flow out of your sprinkler heads. Nozzle changes may be necessary.

I wish that part of the tutorial had been more clear, but I believe that's what it means when it says a booster pump "may" increase your flow as well. It can't change or boost our available flow, but it can potentially boost the flow put out at the end of the line as compared to what it was putting out at a lesser flow. IF there is more flow available pre pump than you were previously using.

I think in my situation, I would want a large tank supplied by my water meter, and a pump from there if I was really serious about boosting flow and pressure. Then, if my tank and pump were sized properly, I could get whatever flow and pressure I like, within reason. The tank would be refillled at a rate of 7.5 gallons per minute, so I'd have to calculate how many gpm my system would use, compare that to the refill rate, think about how long I'm gonna want to run my zones, and use that to determine what size tank I'd need.

I think I'll just make it work with 7.5 gpm flow and 32 psi &#128514;&#128561;. I've come up with a rough plan on paper and I think I can make it work just fine.


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## TSGarp007 (May 22, 2018)

What does your utility say? They may have a rule requiring their approval before you install a boost pump, and may know if you have more flow available. Then again, if you just design you system for what you have then you won't have to worry about pump maintenance in the future...


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## mwemaxxowner (May 30, 2020)

I could have a 1" tap and a 1" meter installed like next door, but I feel like $1500 for 10 gpm vs 7.5 is not worthwhile. Other than that, they basically said it is what it is. Since a pump wouldn't increase my flow, it's not really beneficial anyway.

As to this part,

"Then again, if you just design you system for what you have then you won't have to worry about pump maintenance in the future..."

Yes I agree. Except Stryker's guide states a few times that you need at least 50 psi design pressure for a rotor head irrigation system.

This is the reason for my asking questions on whether that's a hard rule or not. I think I could carefully put the system together and still deliver 20-25 psi to the sprinkler heads, and the charts do list performance data for that pressure, so I don't see why it won't work. I just haven't had anybody answer those questions yet so I'm not sure.

The reason I started looking at boosting pressure bas because of that statement in the irrigation tutorial.


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## TSGarp007 (May 22, 2018)

Yeah, that make sense regarding the pressure for the sprinklers. I suppose you would have to know what the city pipes look like to be sure, but it sure seems like a pump would increase your pressure and flow. A 3/4" meter should be able to handle more than 7.5 gpm.


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## mwemaxxowner (May 30, 2020)

I have a hard time wrapping my mind around the physics of how it can possibly increase the pressure and NOT the flow. But two pump manufacturers I've consulted with both told me the same thing.

I have a 3/4 meter, let's pretend the piping behind the meter is also 3/4 (I'm sure it's larger though). 3/4 pipe can flow at least 20 gpm just fine.

Anyway, when I was on the phone with the guy over the town water, he kept just telling me "what you do with an irrigation system is, you just use smaller nozzles".

Well I know that but eventually they're so small my heads are misting and it also has to run forever to put down enough water. &#129318;&#127996;‍♂ I just said yessir I know, since he was talking to me like he was schooling me up and 32/7.5 is just fine.

Through the course of our conversation, when I was picking his brain about whether my pressure is typical for our street, and whether he can increase it any, I did say a couple of times "I know I can use a booster pump if I have to to help me" and he never said anything about me not being able to.

So, I didn't "ask" him, but I mentioned it and he didn't say no.

At any rate, after crunching numbers and sketching this out, I'm thinking if I continue to use 2" and 1.25" pipe, I can deliver AT LEAST 6 gpm to the zones, and 20-25 psi to my heads. I really think I can work with that, and 20' spacing between heads fits into each portion of my property really well. I think it came out to 10 zones, and I just so happen to have a 12 zone Rainbird controller with only 2 zones in use now!


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## TSGarp007 (May 22, 2018)

That's lucky about your controller. Big caveat, I'm not an expert, but the way I understand it, the pump increases the energy in your system, but total energy includes dynamic pressure (static psi) + flow energy (gpm). So if you are using a pump, the more flow you use, the static pressure goes down. The pump should come with a pressure/flow curve chart that would show the relationship, like this:



So, IF there was enough water behind your meter to handle it, I would think the pump line labeled 'MQ 3-45' would give you around 48 psi at 7.5 gpm, and 38 psi at 12 gpm. But that is assuming a starting pressure of 0 psi, and you have 32. I'm not sure if the psi increase would be additive, or if the pump just maxes out at that curve.

The total energy that the pump is able to add can't really change, that's why psi goes down (energy in the form of static pressure) as gpm goes up (energy in the form of dynamic pressure), though it probably varies a bit due to changing efficiency.

But I don't know what's behind your meter. If it's just a few feet of 3/4" pipe connected to a much bigger supply line, then I would think there is a lot of water for you to pull from. For instance your 1" metered neighbor is getting 10 gpm, probably also at 32 psi. I would think you can increase your overall energy and get that same 10gpm. Maybe if you're not happy with the pressure/performance once your design is complete, you could go back and add one.

Maybe someone will eventually come on and give a boost pump 101...


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## mwemaxxowner (May 30, 2020)

Yes, next door is also 32 psi. His irrigation meter, my house meter, and my irrigation meter are all 32 psi. Both of mine give me about 7.5 gpm.

The boost pressures are additive. I do know that. So, I would search for a 20-30 psi pump at whatever gpm I thought would be sufficient.

I think I can make the new irrigation I want to run work fine as is.

But there are two existing zones both using 6 Rainbird 5004 rotors. I'm afraid when I tie my meter to those it may not drive them very well. If that is the case, I may want to look into boosting just those two zones. If I tie in and I can adjust some nozzles and it works okay, I'll be golden. I think.


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## TSGarp007 (May 22, 2018)

Yeah, your utility company is not doing you any favors, that pressure and flow is really low. Double check all you pipe pressure loss for all your runs. I would design it to have negligible loss everywhere. I wouldn't even accept a 1 PSI loss... Then again I really over designed my own pipes, I guess that's just what I do.


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## mwemaxxowner (May 30, 2020)

That's what I've done. 2" mains, 1.25" laterals.

According to the charts 1.25" mains would be negligible, almost non existent losses too.


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## Deltahedge (Apr 1, 2020)

I'm also curious about booster pumps (And potentially flowing water into a tank and pumping it out) for a slightly different reason than you, but related. I have about 25k sq ft of irrigated lawn on 21 zones. It takes my system nearly 11 hours to run through all the zones and put out 0.50" of water. I have considered breaking my watering into 2 programs to split the watering in half and just running the programs on different days. 11 hours to run the entire program will break the recommendations one way or the other. I have to chose between starting at night to finish in the morning, or start at dusk to finish in the evening.


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## mwemaxxowner (May 30, 2020)

I'd like one for my house also. 7.5/32 at the meter, and my main line is 3/4 pex about 85' long. I had great water pressure at my old house. Comparatively, our showers suck &#128078;&#127996;.


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## g-man (Jun 15, 2017)

3/4 PEX for 85ft is a problem. 3/4pex is like 1/2 copper.


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## mwemaxxowner (May 30, 2020)

I know.


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## TSGarp007 (May 22, 2018)

Your house water is 7.5 gpm at 32 psi, and from THERE it has to go through 85' of 3/4 pex? That is not good.

I had a water softener loop put it and the plumber said he would size the pipe as necessary. He put in 3/4" pex. I made him redo the work and increase the size by showing him the pressure loss table. I was losing more pressure from that pipe run (almost 100') than from the water softener itself. Absurd. But I was starting with over 50 psi, not 32...


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## mwemaxxowner (May 30, 2020)

Yep

I dug down and tapped into it about 10' past the meter and added a spigot there, and and that spigot I get 7.5 gpm.

The other spigot I have at the end of my main line, before it branches into the house, gives me 5 gpm.

The house is sufficient ish though. It is what it is, I'm not going through the trouble to replace that main any time soon. It's not off the radar, but it's near the bottom of a list of priorities though.


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## mwemaxxowner (May 30, 2020)

Well, they ran me a larger supply line. Which I'm extremely grateful for. They certainly didn't have to do that, I didn't ask them to. The last time we talked he said he'd "see what he could do to make it better for me". I certainly didn't think that would mean running me a larger supply line like this. Not when my flow/psi was already acceptable. Marginal, but acceptable. And it's not like I was raising Cain (as my Momma says) about it.

Anyway, I don't know EXACTLY what they did, but he told me he thought I was "on a small line over there" when I talked to him last, and he might be able to get me on "the big line". I'll call tomorrow and thank them and ask exactly what was done.

So, I have a small improvement. I still have 32 psi, but previously it took me 40 seconds to fill my 5 gal bucket (7.5 gpm), now I can fill it in 35 seconds, which is 8.5 gpm.

This is a marginal increase, but even so does give me slightly more flexibility with either nozzle choices, or number of heads. Especially in my zones with few or no 360° heads.


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## TSGarp007 (May 22, 2018)

Hey, that's nice of them! Every little bit helps when it comes to your sprinklers...


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## g-man (Jun 15, 2017)

That's calls for hand delivering a case of cold beer. Maybe the booster pump can help you.

It's been more than 15 years since I took a fluid dynamics/thermo class. I know we discussed booster pumps. Impeller vs piston made a difference, I just don't recall.


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## dwaugh (Aug 25, 2020)

g-man said:


> That's calls for hand delivering a case of cold beer. Maybe the booster pump can help you.
> 
> It's been more than 15 years since I took a fluid dynamics/thermo class. I know we discussed booster pumps. Impeller vs piston made a difference, I just don't recall.


I think Froude and Reynold's numbers are involved, I'm fairly certain I never understood those.


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## mwemaxxowner (May 30, 2020)

I guess if we were near the maximal flow of the meter, main line, or supply piping it would make sense to me.

Since I'm not, and not even close to it, it seems toe that a pump would pull more gallons through in a given period of time.

However, both experts I've talked to told me they will not.

I'm not sure if that's ALWAYS true, or if it's possible under specific circumstances, and they state that a pump will not increase flow to protect themselves and not give someone expectations that may not come true.

In their eyes, perhaps, most of the time flow is closer to the max of the pipe, and if they go around telling folks a pump can increase flow, and it doesn't, a customer may be upset about it.

I don't know. I do believe that I can achieve my goals without one, though.


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## mwemaxxowner (May 30, 2020)

I've sort of come full circle on this. I'm certain these days that I can't increase flow, I've got that.

I'm not, however, as certain as I used to be that a pump won't help me.

I was thinking of using 3500 rotors at 20' spacing, which works out really well with the dimensions of my property. I would set my zones up for 6 gpm. 2-3 heads per zone depending on how the shape is and the arc needed there. I have 40' between my house and the road, so 20' spacing works really well, and falls into place pretty well when I round the corner onto the side yard as well.

After studying the charts some, it looks to me like if I add a +20 or +30 psi booster pump, I can use 5004 rotors with 40' spacing. This simplifies my plumbing a little, eliminates a few heads, and will actually help me eliminate a zone or two, and save a little money on pipe/valves. I'd still set the zone up for 6 gpm, but if I can get 45 psi to the heads I can use 40' spacing. I think.

Thoughts here? I'm having trouble looking through websites online and finding a pump that's only +20 or +30 psi at around 8 gpm.


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## rotolow (May 13, 2020)

mwemaxxowner said:


> After studying the charts some, it looks to me like if I add a +20 or +30 psi booster pump, I can use 5004 rotors with 40' spacing. This simplifies my plumbing a little, eliminates a few heads, and will actually help me eliminate a zone or two, and save a little money on pipe/valves. I'd still set the zone up for 6 gpm, but if I can get 45 psi to the heads I can use 40' spacing. I think.
> 
> Thoughts here? I'm having trouble looking through websites online and finding a pump that's only +20 or +30 psi at around 8 gpm.


Tested some 40' spacing with 5004's and even the slightest breeze significantly impacted the max throw distance of my rotors. YMMV.

My reliable pattern was 25-30' on 5004's. Just my experience.


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## mwemaxxowner (May 30, 2020)

And that was with ample flow to match whatever pressure you had?

If so, that seals the deal I think. I'll stick to my 20' spacing and 3500 heads. Thank you very much!


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## Wiley (Dec 2, 2019)

rotolow said:


> mwemaxxowner said:
> 
> 
> > After studying the charts some, it looks to me like if I add a +20 or +30 psi booster pump, I can use 5004 rotors with 40' spacing. This simplifies my plumbing a little, eliminates a few heads, and will actually help me eliminate a zone or two, and save a little money on pipe/valves. I'd still set the zone up for 6 gpm, but if I can get 45 psi to the heads I can use 40' spacing. I think.
> ...


I have similar thoughts. I have one area where I have 45' spacing with 5004's on a 90 and have trouble on windy days. I like the 20' spacing with the 3500's where you may be able to employ a little better overlap.


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## mwemaxxowner (May 30, 2020)

That was my original plan, and I've already spent a lot of time planning it out. I'll stay the course. Thanks!


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## Greendoc (Mar 24, 2018)

A 3/4" water meter can flow 20 GPM. What a booster pump will do is pressurize the water above your incoming pressure and draw up to that 20 GPM limit. There is nothing wrong with throttling the outgoing flow of a pump within reason as long as the pump is not deadheaded(water flow 100%) off. Single stream rotors need 40-50 PSI at the head not at the point of connection or beginning of the zone. At the head. I can tell when that requirement has not been met. Lawns have dry spots in between each head placement. In addition to excessive watering occurring at the end of each stream.


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## mwemaxxowner (May 30, 2020)

But if I only have 8.5 gpm the pump won't increase gpm over what I already have flowing, right? That's what I keep being told &#129318;&#127996;‍♂&#129335;‍♂. They put in a larger supply line on my street which bumped me from 7.5 to 8.5, so I don't know where the choke point is, or what's responsible for the low flow. The guy over the water company just keeps saying "he doesn't know why our pressure is so low".

The irrigation system that was already on this property, and next door, was designed and running on 10 gpm and 32psi static pressure.

That works at least well enough to satisfy me. The portion of my yard that was running on that system last year looked nice with no other intervention from me.

The charts have specs for 25, 35, 45 psi (etc). If I consult that chart for the 3500, use the proper recommended nozzle for 25 psi (if I have 25 after friction losses) and have 20' head spacing you still don't think it will work? I'm currently using impacts and one pop up RB impact. Do you have any experience using those with 25 psi at the head and 20' spacing?

If I boost the pressure I don't think I can run 20' head spacing, and 30' spacing doesn't fit the dimensions very well in many places. If I have to boost the pressure but still live with the 8 gpm that's certainly doable, but I guess I'd need to look at other types of heads in the front where it's roughly 40' from the road to the house.


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