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Pressure drop question

3K views 37 replies 12 participants last post by  PurpHaze 
#1 ·
Long story short...

I am one of those dreaded home owners. I am in process of having a pool built and re-connecting and tweaking my irrigation system. Have read thru and completed Jess Stryker's tutorials and have had Rainbird Design Service design a system for me.

I have had estimates from irrigation pros who want to charge me $600 to $1400 to reconnect my system (including $275 for a Rainbird ESP-4MI with only one module). I'm ready to tackle the task.

My question is...how do you design for a daily pressure drop?

I live in the Orlando, Fl area and during the winter months is when most people water their lawns. There are times that so many people are watering at once, that the water pressure inside my home is nearly gone. Showering is sometimes an impossible task. A 1/4 diameter stream of water comes from the kitchen sink.

My static pressure is 65, 5/8" meter, my 1" pvc sprinkler mainline POC is within 6" of the meter and I estimate 10-12 GPM (on a good day and during the summer months).

Thanks

Ed Geary
Clermont, Fl
 
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#3 ·
unfortunately county code states wells have to be within a specific distance from each other. Neighbors around me, who built their houses a few years befor mine, have the wells.

Another reason I would want to stay away from using Florida well water is that it has a high iron content and it stains everything that it comes in contact with. Many houses, driveways and fences look like they are rusting.
 
#4 ·
True enough about the iron, although there are neutralizing chemicals that can be fed into the sprinkling water to eliminate the staining. At some point, I could see most of Florida going to secondary watering supplies for the sprinkling. Folks with extra space can set up a pressure tank or two, and a booster pump, and maintain water pressure in their homes.
 
#5 ·
My static pressure is 65, 5/8" meter, my 1" pvc sprinkler mainline POC is within 6" of the meter and I estimate 10-12 GPM

Ed,
I often see the same setup here... 5/8'' meter, 1inch main
If you can upsize the meter that often helps. Otherwise try scheduling the irrigation to run at a better time. I know here 5-8pm is a heavy water use time. Obviously best to water before sunup but most people like to see it running, etc

drew
 
#8 ·
currently in place are Hunter Rotary sprinklers. I have no idea what valves are installed.

Given the current installation (heads are connected directly to pvc elbows), contractor most likely never used anything but the pre-installed valve.

I am replacing all heads with new Hunter PGP rotaries. I planned to select nozzle according to angle of rotation (for example #3 for 90 degree, #5 for 180 and #7 for the 360's).

also replacing valves with the Hunter PGV 1" jar top valves and replacing controller with a Rainbird ESP-4MI.

Back yard will be going from 4 zones to 7 zones.

One side of front yard is covered with Hunter 4" pop-up sprinklers. Never an issue of pressure drop off. Grass always looks great there.
 
#11 ·
the irrigation pro that gave me the $1400 estimate had a Rainbird ESP with him. I liked the simpicity of the operation and especially the capability of expanding to 13 zones.

I have already purchased my equipment and at the time didn't realize the Pro-C was expandable to 15 zones.

My property is just under a 1/2 acre, so I guess I can make do with "only" 13 zones. :)

I found the Hunter and the Rainbird to be equal in price.

I paid about $105 for the controller and two modules at MTI.

Plus....the Rainbird design center designs are free with the Rainbird product.
 
#12 ·
Sounds like you've done your homework. After that it's the school of "hard knocks". One thing you don't want to do is "try and save a penny." It will cost you more in headaches and water usage. MTI should be able to help you with questions and local codes.
 
#13 ·
I know you like your green grass but sometimes you have to adjust to low water situations by re-thinking your landscaping. You can keep your green grass in the front yard where there is good pressure, and remove the grass from the back.
Re-landscaping with drought resistant plantings and hardscaping like paver pathways or colored graveled pathways between planting beds.
Then water with a drip irrigation system off one or two stations of your controller. I know the homeowners of California where I live have removed water guzzling lawn landscapes and gone with water wize plantings instead.
Hardscaped sitting areas are used quite a bit, as well as well placed small palms such as, Lady palm (Rapis)-Bamboo palm(Camaedorea)-Pigmy Date Palm(Phoenix roebelenii) and Chinese fountain palm(Livistonia chinensis).
Probably not the solution you are seeking but it's a suggestion you might keep in mind if your sprinkler replacements and adjustments don't correct the pressure problem.
 
#14 ·
I have actually done a lot of the things you recomend. I have areas in my back yard that are planted with with drought resisitant native plants and pine trees. At this time I have 20 pine trees growing in my yard.

I'm into backpacking and love being in the forest and have created a little patch of "woods" where I can hang 4 hammocks around a camp fire or a deep frying turkey.

But still, there is that darn grass in between these woodsie areas and the new pool that needs frequent attention.

I know this is unusual for someone living in Florida, but I hate palms. Don't like the way they look and are way too much maintenance for me.

The only palms I like are Saw Palmetto bushes and they just grow too darn slow. The couple I have are 5 years old and only about 14" high.
 
#15 ·
If the front yard coverage is good, and the back yard coverage is poor, then you want to try swapping nozzles around. If it works out, with equal nozzles and equal spacing, the back yard sprinklers are still underperforming, then you might look at increasing the size of the pipe feeding the back yard. (or maybe trying smaller nozzle sizes in the heads, and living with longer run times)
 
#16 ·
yea, the section of the frontt yard covered with the pop-up sprayers is excellent. the remainder of the front yard has rotary's and also get's the brown spots and green circles.

I will try a combination of yours and Drew's suggestions - try different nozzle selections, try different watering times and measure the water output to see how long it takes to get 3/4" of water.

My watering times have been 30 minutes for the sprayer zones and an hour for each rotary zone.

thanks!
 
#17 ·
One more possibility to squeze out the last possible bit of performance from a low-pressure system, is to try a Rainbird Maxipaw impact head. These will spray further at low pressure than any rotor head. Not a pro's first choice, but sometimes curcumstances dictate.
 
#18 ·
Ed G said:
My question is...how do you design for a daily pressure drop?
Unless you measure your static/dynamic pressure during the actual time the system is going to run you won't get an accurate accounting of your available pressure. You'd be designing and installing a system that works fine during the time you initially measured PSI/GPM but piddles partly or entirely when it's running during its watering window. (There are plumbing companies that can install a test pressure gauge with graph capabilities that will record actual pressure over a 24 hour period but I don't know what they'd charge.)

For example... We have one school site on domestic water source where it's impossible to service the system prior to around 10:00 am because only 2 of 7-9 sprinklers (Hunter I-40s) in a zone will even pop up. There is just too much draw-down from the surrounding residential tracts prior to that time to even try and fire the system. However, these same zones work fine during their watering window between 11:00 pm and 4:00 am and the grass is kept green without irrigation gaps.

One of my brothers used to live in the tracts surrounding this school. His home included a front irrigation system that worked fine when he first moved in. Then, as more and more homes were built in the surrounding area, his yard started developing brown areas as were his neighbors' yards. His controller was set to water starting around 6:00 am so that the "irrigation water on the grass blades would dry off from the morning sun and there'd be less chance of fungal problems" just like everyone else is instructed. I changed his system start time to 3:00 am and his yard immediately recovered.
 
#19 ·
Ed G said:
currently in place are Hunter Rotary sprinklers.
What model? I-20s?

I am replacing all heads with new Hunter PGP rotaries.
The Hunter PGP pressure specifications are nearly identical to the Hunter I-20s.

PGP: 40-60 PSI recommended; 20-100 PSI operating range; 52' maximum radius.

I-20: 40-60 PSI recommended; 20-100 PSI operating range; 47' maximum radius.

Medium and large rotors are notorious for not operating effectively at their lowest operating range with larger nozzles and often leave "donuts".

However, the Hunter PGJ has a minimum recommended operating pressure of 30 PSI but they may not have the radius you desire. Maximum of 37' radius.

Back yard will be going from 4 zones to 7 zones.
Even this may not help. This may only help if your piping is undersized in some manner.

One side of front yard is covered with Hunter 4" pop-up sprinklers. Never an issue of pressure drop off. Grass always looks great there.
Three of the four Hunter spray pop-ups (SRS, Pro-Spray, Institutional Spray) work at a recommended minimum pressure of 15 PSI. The remaining model (PS) has a recommended minimum pressure of 20 PSI. This is why they'll work at lower pressures when rotors fail.
 
#20 ·
Thank you PurpleHaze. The draw down you are describing is exactly what I am experiencing.

I will change watering times and days.

My design goes for the "head to head" coverage and I max out at a 32 1/2 foot radius.

I am a Mechanical Draftsman and I have laid out my sprinkler design in Autocad. What kind of format could I put the dwg in so you guys could take a peek at my design?

Being able to send Rainbird the layout in autocad made for a very accurate design from them. They were able to import the autocad file directly into RainCad.
 
#24 ·
mojob said:
Does anyone else out there besides me feel sorry for the "irrigation pros" that took the time to go out to this guys house and work up a plan and quote him a price just for him to turn to us to get some more free advice? Sounds to me like a huge PITA.
Yanno you got a point. Let a new contractor trying to learn the ropes ask questions of how you do it, and most generally the response is "Do a search and look it up." But let a DIYer ask the same questions and people can't seem to give them enough advice. Go figure.
 
#25 ·
I dunno, I think lawn sprinkler work in Florida is fairly accessible, so long as obscure stuff like indexing valves and pump problems aren't involved. The variable pressure problem is reason enough to make inquiries
DeepRoots said:
I probably have enough 'spare' nozzles to fill up a dumptruck. I'd be happy to mail you a box of them.
Reminds me of the time I got a letter from one ambitious homeowner, who wanted to see if anyone in the sprinkler trade wanted to purchase his old electromechanical controller. Unfortunately, I had done some recent housecleaning, or I would have boxed up half a dozen or so identical units and mailed them to him, with my compliments.
 
#26 ·
"Does anyone else out there besides me feel sorry for the "irrigation pros" that took the time to go out to this guys house and work up a plan and quote him a price just for him to turn to us to get some more free advice? Sounds to me like a huge PITA."

IF an irrigation pro HAD worked up a plan for me, I most likely would be using his services and not be bothering you professionals.

Three irrigation guys came to my house. One looked at my back yard and told me oh, this will run about $800 - $1000. Nothing in writing. No plan worked up

One quoted $500 - $650. Nothing in writing. No plan worked up

The third wrote up an estimate for $1000 in parts and $400 labor. Then he also handed me an invoice for a $65.00 estimate fee and tells me: "if you agree to our service, this estimate will be deducted from the total". No plan was worked up.

Believe me, it was more of a pain in the ass for me than it was for the contractors who did show up to give me a quick verbal quote.

An important thing to keep in mind though, is that the homeowners who come to this site looking for guidance, do take notice and purchase from the advertisors who sponsor this site.

The owner of this site may not want homeowners run off.


DeepRoots: I surely do appreciate your generous offer. My next door neighbor is a Supervisor for Massey Green Up (landsape mainenance company) and he has access to the spare nozzles. He knows weeds, but doesn't know irrigation. BUT...if you have spare gray nozzles, I'd be interested in them.

PurpleHaze: Thank you. I will be emailing the dwg today or tomorrow. Today is dedicated to being out on the lake wakesurfing.

If you guys ever head down to Rat World I'd be more than happy to exchange a day waterskiing, wakeboarding or wakesurfing for the advice you are giving me!
 
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