Mixed Up About Pressure & Potential. Garden Areas

gamountainsMarch 10, 2012


Situation: Irrigating two zoned garden areas. Dimensions 5 x 125 feet and 15 x 100 feet. Planning on using a gas powered Honda VX10 portable water pump from a creek source 35 feet below garden areas. Electric power out of the question...too far. Other pump types not feasible..creek flow slow and no drop offs.

According to Honda I will get 15 psi at the head with a flow of 35 gallons per minute. The 5 x 125 area slopes downward from the head about 10 feet. The other area remains flat. I was planning on a T connection at the head to irrigate the two areas separately, thinking I don't have enough pressure to try it all at once.

Looking to run bubblers or micro sprayers in the two separate lines spaced accordingly(depends on potential). I realize the more outlets the more the pressure drops. What has me baffled, and it's probably quite simple...Will the pump be affected if I have too much pressure on it? In other words, it says 35 gpm, but let's say the irrigation system is set up where only 10 gpm comes out. Too much stress on the pump? It will probably only be used 1-2 times per week June to September for an hour each time.

Btw, maybe I may thinking into this too much as the pump does have a throttle. It's probably a test, test and test scenario, but thought someone could make it simple..or is it simple?

Lastly, a cistern has been considered for a gravity irrigation system but I'm hoping to get around it(another reason why I am here). Can anyone point me in the direction in what to use in so far as type of system..ie.coils, heads etc. Yes each and every situation is subjective...but thanks in advance.

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although I do not know much about the type of pump you plan to use, pressure does not seem to be the problem. the extra water volume is what will cause you trouble unless you allow for the excess to flow back to the creek. if your lines are capped I would think the pump would blow out some of your fittings.

    Bookmark   March 12, 2012 at 6:46AM
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Contact the maker of the pump and find out its MAX psi. Many of these pumps have very low max psi and will not work properly for irrigation. If the max psi is between 40-65 you will be fine but I am going to guess your going to have serious pressure issues on that type of pump. But without the numbers you can't get a good answer.

BTW, standard spray heads want between 25-45 PSI at the heads. Drip/micro spray get away with a good bit less but still 15 psi is low. Try to get a performance curve on the pump.

Good luck,

    Bookmark   March 12, 2012 at 5:15PM
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I agree with TP. You will also need a good filtering system for the heads you will using which will eat up pressure and it is always easier to reduce pressure with a regulator than not have enough system pressure for the system to distribute water evenly and to all plants as they mature. Your drop in vertical height of 10 feet along your garden plot will give you about 5 psi additional pressure at the bottom. Not much difference. JMHO Aloha

    Bookmark   March 12, 2012 at 11:24PM
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Yes I plan to make a visit to a local dealer and ask questions. In the meantime here is an performance chart(link below). The creek water is very clean but I do plan an additional filtering device just in case. I have been using another pump for four years now that I basically plop in the creek. No problems, but it won't go higher than a 15 feet head.

Incidentally one of their promotion pics shows this.


Here is a link that might be useful:

    Bookmark   March 13, 2012 at 7:44AM
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Ok from that chart this is what I would do.

I would run as large a pipe from the water source through the pump and up to the garden area as I could. Pump picture didnt come out on my computer but I will guess it is either 1 1/2" or 2" pipe. Whichever it is run that size to your garden areas.

Second, on the 5' wide plot I would run what are called 4X15 Side strip heads. You will also need either 2 Endstrip heads or 2 10' quarter heads (I would most likely go with the 10' quarter but either will do) I prefer Toro heads but use any brand you choose. I would run the first head at the beginning of the bed and use the 10' quarter then space the heads as equal as you can (dont go crazy its not that important they are 100% equal) with the heads about 6-8' apart. This will give you very good overlap. So you will need 17 (or so) 4X30 sidestrips with the 2 end heads.

Your other bed is a bit more difficult. How thick the bed is going to be with plants could change this alot but I would most likely go with 10' heads all around. A quarter head on each corner and half heads spaced 10' all the way around. Then a row of full heads down the middle spaced 10' apart. If I was on the site I might change this but this should work on almost all plantings. This will give you 4 quarter heads 9 full heads and 18 or 20 half heads (depends on if your going to put an extra head in the middle of the 15 foot sides.)

The 5X125' bed will use approx 18 gallons per min. And the 15X100' plot will use between 20-25 gallons per min. On your pump both of these systems will run as one zone each and still be in a good range of your pumps preformance. If these were my system I would most likely make the 15X100' bed 2 zones. One would run the outside heads and one for the full heads down the middle. So you can run them together or shut off the middle when you need less water.

Anyways thats alot of info.

Good luck,

    Bookmark   March 13, 2012 at 11:26AM
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Hey thanks Tom! Lot's to consider. I wasn't even thinking about the different sprinkler heads as the area is along a gravel driveway. The pump has one inch outlets. I had originally thought one inch pipe from the pump than someone suggested one inch rubber hose. It would definitely lay better along the slope climb to the head...pump also self priming(somebody mentioned that)

I'm not sure about the larger area and types of plants. Currently it needs quite a bit of back fill so something can grow there. Poor soil with large rocks three inches below the surface. I really want to load it up with trailing Petunias. By the way, it also slopes (two directions) but I didn't want to complicate the original ideas.

Notice the surrender flag from last year. Mountain Laurel grows there and a few assorted weeds. Lilies are trying but too dry. It's my best full sun spot (I have very little) on the property and one reason why I want to work it. The other area trails the fence line.

    Bookmark   March 14, 2012 at 7:37AM
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