Zone and head question

Discussion in 'Irrigation / Sprinkler Forum' started by martin1b, Apr 7, 2007.

  1. martin1b

    martin1b New Member

    Apr 7, 2007
    There was a thread 'zones zones,etc' that was very similar to the questions that I had. I'm getting ready to install my sprinkler system and was wanting to run this past everyone to get their opinion.

    I have a 1.5hp P series Mcdonald pump (performance chart : that is down around 125ft. According to the perf curve, it looks like it can deliver ~20gpm. My testing shows that the well and pump delivers very close to this out of a 1.25" line. My pump switch is set to 50/70psi cutoff and I have a 50 gal pressure tank. Small note is that the water is very hard (~125 grain). To me, this sways my thoughts on types of head (and perhaps valves) to use.

    I was planning on running 1.25" 160psi poly as the trunk and tapping off of that to the valve and going 1" 100psi poly to each head with a blazing saddle and funny pipe into the side of the head. I chose a Rainbird maxipaw head due to the hardness of the water. I've heard that gear heads eventually stop functioning with very hard water due to build up in the gears. Since I want this set up to last a very long time, maxipaws appeared to be the only 'dirty water' head in my price range (~$12/head).

    Head Distance: I was planning on using 4-5 heads per zone and limit/eliminate pump cycling by using different tips. Since the maxipaw has 3gpm - 8gpm tips, I figured that this would work. Thoughts? I have about 1.5 - 2 acres of fescue. As I laid it out, I went 25-30ft between heads. I came up with ~90 heads!! Does this sound correct?? That doesn't even include 1-2spray head zones around the house and 1 to 2 drip zones.

    Controller: With ~90 heads with 4-5 heads/zone, That works out to 23-28 zones!!!! This concerns me but this may just be the nature of the beast. Is there something to do here? Price wise, I was thinking of buying 2 controllers rather than 1 very large controller. 2 Hunters with zone modules maxed out to 24 zones was ~$280 vs 1 24 zone Nelson controller for $400. Plus, if it turns out that I could run more water,I could have 2 controllers watering at once. Thoughts?

    Valves : Any suggestions on valves? I was considering the Hunter PGV100MB valves and making a manifold out of PVC, then go back to poly. Ideas or best practices?

    Drains : Any suggestions on a most effective drain type, locations and amounts? I was considering using gravel or rock rather than sand so as to not clog up the valve. Also, i was planning on putting main line and zone drains at the lowest point. i was also planning on putting a drain near the valves just in case, so any standing water wont damage the valves. This needs to work properly because here in Kansas, we get all kinds of wierd weather. Shoot, it's the first week of April and we usually are pretty warm here. Today, it's 32 degrees.

    Am I way off here?
    Last edited: Apr 7, 2007
  2. Wet_Boots

    Wet_Boots Sprinkler Guy

    Mar 23, 2007
    Metro NYC
    Are you digging trenches to install the pipe? Poly is more cold-resistant than PVC, but I'd probably bump up the mainline to inch-and-a-half, if it's going to be a long one.

    Hard water is not a big issue. On brass control valves, maybe. Not elsewhere. Heads will stop turning when they're ready to do so. Maxipaws have their own reliability issues. They are good with a water supply that contains a lot of sand.

    You can do fine with spacing of 35 feet. Even further, if you know how to design, but closer head spacing will cover up a lot of mistakes. Unless you have really sandy soil, you should be able to get by with less than 20 zones.

    Consider doing without drip. Not that the concept is faulty, but the realization is problematical. With sprays, you can see when heads aren't working. With drip, you know it's not working when your plants die.

    A Hunter ICC controller can be expanded to 32 zones, and it does have the ability to run a drip zone concurrently with a lawn zone.

    Try to build valve manifolds without any PVC fittings with female threads. Male x Barb valves might be a problem (having to do with the valve body material)

    No drains. Systems survive the winter because they are blown out with an air compressor.

    If your pump is the one that supplies your drinking water, and even if it isn't, in some locations, you must install a backflow preventer in the sprinkler supply line. On flat ground, a pressure vacuum breaker (PVB) is the simplest device you can use. Located higher than the highest pipe or sprinkler it feeds, its function is gravity-based.
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  4. martin1b

    martin1b New Member

    Apr 7, 2007
    I was planning on vibrating it in rather than trenching. The main line is only going to be 100 ft -150ft long from ground level of the pump.

    I'm really concerned about hard water and locking up. However, you're correct about the maxipaws and junk getting into the sprinkler. But, with 90 heads, I hate to find out and eventually replace every one of them. Does anybody have experience with very hard water, geared heads and 10 years + of use? I really would like to go that route. I'm just concerned about reliability with the hard water. If I were to go geared head, what is a very reliable head?

    Thanks on the ICC controller. Looks like a perfect fit. And the price is very comparable.

    What's the best way to build the valve manifold? Any valves that you've had great luck with? What's the most fool proof type of connectors to get when your coming from 1 1/4 poly down to 1" poly > valve > 1" poly
  5. Wet_Boots

    Wet_Boots Sprinkler Guy

    Mar 23, 2007
    Metro NYC
    The only water buildup I see on plastic heads is from iron. And water supplies I know to have built up on brass valves are not causing problems in plastic valves and heads.

    Speaking of heads, you will be replacing them. Nature of the beast. Doing a design with less heads will give you less to replace. Maxipaws can be fitted with nozzles that use less than 2 gpm, for heads in corners, in combination with half or full circle heads using higher gpm.

    Valves are a tougher call, since the amount of sand you're pumping isn't known. You might need a strainer to protect valve operation. I would install a 100 mesh Vu-Flow on any well, with the idea of allowing me to stick with standard valves and heads. Poll a group of installers, and you might hear the most recommendations for Rainbird 100-DVF valves. Valves with 1" FPT connections build the strongest manifolds, and allow you to exit the valve with larger poly pipe, if needed.
  6. Bob NH

    Bob NH In the Trades

    Oct 20, 2005
    New Hampshire
    You can get poly fittings in female adapter form, tees with female outlets and female els.

    I have a little trick for making manifolds with PVC. I use cemented tees and use half of a Schedule 80 PVC nipple to connect the valves. It is one less joint/piece than using a male adapter and the schedule 80 is a good part to screw the valve onto. The schedule 80 nipples are available from Grainger and I'm sure others.

    If you can get to 35 ft spacing vs 25 you will save half of the heads.
  7. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego
    2 acres is a lot of grass!

    In sprinkler design, everything is a compromise....GPM, coverage, # of heads. Your heads need to overlap. If you select a head with 40' range, they need to be 40' apart ( NOT 80' apart). Most of the good brands, Rainbird, Hunter, K-Rain, etc. have a selection of GPM nozzles available. To minimize the number of heads, use the lowest GPM you can find and use longer watering times. Pray for rain!
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