# I wanna get this right



## jeff+-54 (Jun 12, 2019)

I'm trying to put in an in ground sprinkler system in my yard. I've read the info on irrigationtutorials .com I've gone through all the necessary tables and completed the calculations. My static water pressure is 55 psi on my hose bib. My gpm is 8.8. My meter is 5/8" and main lines are 3/4" copper. After completing the design data form my pressure loss was 58.19. Too much. So I followed the advice of the tutorial and lowered the psi of the sprinkler to 30 from forty. Now the pressure loss is 48.19. Can I use MP rotators if I follow the 30 psi radius listed in the sprinkler design data to get the proper head spacing? Thanks!


----------



## g-man (Jun 15, 2017)

Can you post your layout? And pipe sizes? 58psi drop in psi is a lot. The 8gpm is a bucket test?


----------



## jeff+-54 (Jun 12, 2019)

I'm still working on my drawing and layout but I will post ASAP. Thanks.


----------



## jeff+-54 (Jun 12, 2019)

I wanna use 1" or 1.25" schedule 40 for main lines and 1" class 200 for laterals.


----------



## jeff+-54 (Jun 12, 2019)

Yes my gpm was a bucket test.


----------



## jeff+-54 (Jun 12, 2019)

Ok so my hat is off to the people that do this on a daily basis. Not much to it after the first 500 times lol! 
It's like a puzzle to me getting the sprinklers in the right place to insure proper coverage. I've attached pics of my design work sheet from irrigationtutoials.com as well as my sprinkler layout. Any advice, pointers, suggestions, and words of wisdom are much appreciated. 
I arranged the sprinklers as 30psi. I know 40 is optimal for no rotators, but not sure if I have that.


----------



## TSGarp007 (May 22, 2018)

You measured your pressure at the hose bib right? So I think you can ignore the two 'House Mainline' PSI lines. Also take away the backflow preventer loss IF your hose bib is after the backflow preventer (one of mine is). You need to calculate pressure drop AFTER the point at which you measured the pressure. That will really help you out I think!


----------



## g-man (Jun 15, 2017)

In the back there is an area that does not have head to head coverage (near the pool). There is also a 360 head that will spray the neighbor's yard.

In your PSI table, you are taking 30PSI at the heads. That's not the pressure loss at the head. The 30 or 40 psi heads means that they try to limit the pressure the nozzle see to 30/40 psi. If the pressure going into the head is 80psi, they limit the nozzle to avoid misting.

I tried to find how much pressure loss you could get from the head, but a quick google did not find it. I think it is not a lot. If your line pressure is above 40psi, they will work.


----------



## TSGarp007 (May 22, 2018)

I never used that tutorial table, it seems confusing. Maybe instead it should just have starting pressure, then a section you might subtract, and then the remainder equals sprinkler pressure. Then if that pressure is below sprinkler design specs you have a problem, and need to redesign something. That would be more Intuitive (to me anyway).


----------



## jeff+-54 (Jun 12, 2019)

Ok so two weeks later I'm working on my plan again. I added a head and moved two others just to the right (south) of the pool. Also I reduced the 360 degree head to a 270 on the NE corner. I am now trying to group these heads and draw in my lateral lines.

Before I do I have a question, is it better to run the main line all the way around the house and put valves over there or keep valves on the south and just run the laterals all the way around? Seems to me that the second option would be better. Less pipe under pressure all the time maybe less pressure loss to the zone/system. But it might cost more? Thanks in advance for your guidance.


----------



## jeff+-54 (Jun 12, 2019)

Ok just thought of another quick question. When grouping heads in zones, how close do I need to stay to my design flow (8.8 gpm)? The table in the tutorial gave a maximum safe gpm of 11 gpm. Am I wrong in thinking if I stay between those numbers it will operate properly?


----------



## TSGarp007 (May 22, 2018)

I would personally keep my gpm under the minimum I know I have. You may have more than 8.8 if you measured from a hose bib, but I wouldn't go over that unless I physically verified some other way. Once you get to cutting pipe to install your system, you could do a real gpm test by bypassing the hose bib.

As for the valve placement, it's really just your preference. All you have to do is size the pipe appropriately for the gpm and length of each segment to make sure you don't have too much pressure loss, which is always true regardless. If you want to put some valves in a different location, but also don't want the pipe to be pressurized all the time, then you can use a master valve. I had that concern when I did my project, and this site clued me into that. It's really easy, no harder than adding one more normal valve to your system and making sure your controller has a master valve option. I have three different valve box locations.


----------



## GrassOnTheHills (Jul 3, 2020)

Hey @jeff+-54 , I too am installing an in-ground system shortly and also went through EVERYTHING on irrigation tutorials. I wanted to comment on a few things from this thread that may be pointing you in the wrong direction, and maybe offer some advice on what you could do to get your design right.



> You measured your pressure at the hose bib right? So I think you can ignore the two 'House Mainline' PSI lines.


I'm new to this, so don't take what I'm saying as an expert's advice, but this thinking is explicitly called out on the tutorials as being incorrect. If people are curious, I can find and link the exact page. But the idea is that once you have water FLOWING, the PSI loss from the mainlines is indeed a factor. I factored this in when designing my system. I also have 3/4" lines coming in, and those are a real PSI loss factor.

Another thing to call out is that you shouldn't really be using a bucket test to measure GPM. This is also called out in the tutorials. You should be using "safe flow" which is the flow at which your velocity does not exceed a safe limit. These limits are detailed in the charts on that site, but to be safe I stayed at 7-8GPM which means more zones but less flow. My house is also 50 years old, so I don't know how much life these pipes have on them. I don't want to be scrubbing or causing water hammer. Luckily, your hose bib puts out nearly a safe flow, so you may be OK.

Last thing: I, like you, spent a lot of time designing the system. In addition, though, I sent a request for design to Rain Bird to get them to do one for me. I paid to have it returned faster so I had time to purchase my supplies. They did a great job and the design was nearly the same as what I had. But they give you an inventory list and a discount at their store for using them, which also was really helpful. Just something to think about; it may be too late for you to do this.

Please feel free to DM me with questions or just to discuss your installation/plans! Happy to share mine, especially since we have very similar specs. Good luck with everything.


----------



## TSGarp007 (May 22, 2018)

GrassOnTheHills said:


> Hey @jeff+-54 , I too am installing an in-ground system shortly and also went through EVERYTHING on irrigation tutorials. I wanted to comment on a few things from this thread that may be pointing you in the wrong direction, and maybe offer some advice on what you could do to get your design right.
> 
> 
> 
> ...


I would appreciate the link. A lot of good info on that website, but for some reason I find it very difficult to navigate and couldn't find the explanation for that (including psi drop from the street to meter and from meter to irrigation system). Although it does make sense.

As for the bucket test, I think the tutorial says to use the lower of the bucket or 'safe' calculation, right? Unless you identified why the bucket test is inaccurate (identified where the flow is restricted and bypassed it in your design). In this case the bucket test is less than the 'safe' value. So the bucket numbers are more safe, to confuse things.

If designing at 9 gpm, then you can calculate the psi drop from the street at that value, which hopefully drops those values.

@GrassOnTheHills thanks for the input. I may be an internet poster, but I don't mind being shown wrong!


----------



## GrassOnTheHills (Jul 3, 2020)

Here are some quotes, with links:



> The "GPM" value for your new sprinkler system should be based on the size of the existing water supply pipe running to your house. Some do-it-yourself sprinkler system guides have you measure water flow by turning on an existing faucet and timing how long it takes to fill a bucket. Some also suggest using a special gauge that measures the flow. Regardless of how you measure the flow, we now know that just measuring the flow from a faucet results in major errors that can result in your using a irrigation system flow that is way too high for your house's plumbing to handle. When you turn on a faucet the water from it will often flow out at a rate that is way higher than what is safe for the pipe's in your house. While running water for a few minutes at this flow to fill a bucket is relatively harmless, running a sprinkler system at that flow on a regular basis is not. This unsafe high flow results in "water hammer" and "scrubbing" damage to the pipes, two very expensive problems that can destroy the pipes in your house. We are talking thousands of dollars to re-pipe your house! The key here is that when determining the water supply volume the pipe size must be a factor considered.


Source: https://www.irrigationtutorials.com/landscape-sprinkler-system-design-tutorial/

To give an example, my GPM out of the hose bib using a bucket was something like 16GPM-18GPM, MUCH too high for 3/4" copper. I designed for 8GPM.

It's worth reading the Answers to Common Questions section in the City-Slicker water page here https://www.irrigationtutorials.com/gpm-psi-municipal-water-source/ (assuming you get your water from a water company supply)

Regarding the house mainline and its impact on pressure loss:



> Common question: "Can I skip calculating the pressure loss in the house mainline? It is upstream of where I measured my static water pressure." NO! Sorry to yell at you, but it's a huge, common mistake, so I want your attention. When you measured the water pressure you measured "static pressure", that is, the pressure when the water is not moving. There is no pressure loss in pipes when the water is not moving. But when you run the sprinklers the water will be moving, so there WILL be pressure loss in the house mainline as well as the irrigation mainline. Often the pressure loss in the house mainline is substantial. Therefore you must also calculate the pressure loss for the house mainline and add it in with your other pressure losses. For purposes of irrigation design your "house mainline" starts where your house water supply pipe branches off of the water supplier's big water mainline, which is typically in the street or alley. The house mainline ends at the point where you tap into it for your irrigation water.


That's from here: https://www.irrigationtutorials.com/irrigation-mainlines/

Honestly I'd suggest reading every page of the tutorial, ESPECIALLY everything regarding pressure loss. It's really informative and I have a lot of confidence going into the install because I understand how everything ties together now. I also wrote down all my property info and calculations. If I remember later I'll scrub it of personal info and share it as a Google Doc if that'd be helpful at all to you!


----------



## GrassOnTheHills (Jul 3, 2020)

TSGarp007 said:


> GrassOnTheHills said:
> 
> 
> > Hey @jeff+-54 , I too am installing an in-ground system shortly and also went through EVERYTHING on irrigation tutorials. I wanted to comment on a few things from this thread that may be pointing you in the wrong direction, and maybe offer some advice on what you could do to get your design right.
> ...


That's why this forum is awesome. Hopefully my posts don't come across as know-it-all or confrontational. I learned so much from that tutorial site because I read it for weeks, haha, and I would love to be a help to anyone that's going through the same thing.


----------



## TSGarp007 (May 22, 2018)

I think I should make a signature line that says I am probably wrong... lol.

I spent so much time on that tutorial website, I would have thought I saw it all. But, and I may be in the minority, I can't stand the way it is laid out. That being said, for a completely free resource it is amazing. Maybe I did see that portion, but forgot about it when I finally came up with my design. I also failed to see, or remember, the part about a master valve, which someone pointed me to later. I did a LOT of research before doing my design. And then waited a long time after doing the design to doing the install (waited for winter). No doubt I did some things wrong...

Interestingly I did think about this issue though (supply pressure), just didn't attack it that way. I know static pressure goes down when dynamic pressure goes up, thanks to our friend Bernoulli. I measured my water flow rate and pressure simultaneously. Without any water flowing I was in the mid 50s for psi. With my hose bib wide open I got 15 gpm which surprised me as high, my simultaneous psi was something between 15-20 psi, lower than I need for the irrigation system. So I closed the hose bib a little to try and get around 10 gpm via the bucket test and my psi went way back up, then I tried 12 gpm and that was good too. So in the end I designed my system to be max 12 gpm. After install I also measured the psi while every zone is running, and they are all where they need to be. From my valves on, my system is significantly over designed, resulting in negligible pressure loss.

I suppose my method leaves open the possibility that the city's pipes prior to my meter are over 7 ft/sec. I think my pipes are fine (1" pipe after the meter). Prior to my renovation, my system had so many sprinklers on so few zones, the gpm was maxed out to the point the sprinklers didn't have enough psi. Much better now.


----------



## g-man (Jun 15, 2017)

One key thing to keep in mind. When you measure gpm in a bucket test using a spigot, it might be less gpm than what you could really do. For example in my house I have 3/4 PEX at the meter and into the house. From there the builder T to the spigot at 1/2in PEX for 20ft with a 12in spigot valve. My gpm at the spigot is low because of the 1/2PEX 20ft. For my install, I T from the 3/4 PEX into 3/4 copper (to reduce my pressure loss). My max safe gpm is based on the 3/4PEX 7ft/sec numbers. BTW, I ended up replacing the spigot line to 3/4 PEX.


----------



## TSGarp007 (May 22, 2018)

@g-man, I recommended OP use his bucket test gpm unless the reason it is less than the 'safe' numbers is identified and doesn't apply to the new irrigation system, or they test at the pipe itself where the irrigation system will start, in which case there will be new bucket numbers. 
That was to be conservative. Is that a good approach?


----------



## g-man (Jun 15, 2017)

He has 58psi static with a 3/4 copper. He can safely do 11GPM. His actual GPM will depend on all the friction losses up to the point of service. The bucket test told him 8.8gpm, but what friction losses he is getting from this path that he wont get once he tap into the main line, I dont know. It it likely higher than 8.8gpm. 10? 11? Measuring post install is a good approach, but at that point you want to continue digging and install and not go back to redesign. Using the 8.8gpm will be a safe bet from a design stand point. That also leaves you some room to flush a toilet in the house too.


----------



## jeff+-54 (Jun 12, 2019)

Wow, that certainly is a lot to consider. My planning/designing continues. Thanks again for your willingness to share your knowledge.


----------



## jeff+-54 (Jun 12, 2019)

Yet another quick question... if I used a shorter radius for the head spacing in my design do I use the gpm for that radius or for the optimal radius?


----------



## TSGarp007 (May 22, 2018)

They are designed to change flow rate as you adjust the arc and radius (up to 25% if at 40 psi), in order to maintain the matched precipitation rates. So in theory the gpm should go down as you decrease the radius. But that table is the gpm based on operation pressure, not radius adjustment. It's probably close though. Still, I would use the full throw gpm for your operating pressure for planning purposes. People often say on here to design the spray pattern to go a couple feet past the sprinkler (so head to a little past the head coverage). You may not quite get the listed radius, and/or it allows for some wind, error in install, etc...


----------



## RVAGuy (Jul 27, 2020)

Why not just design for something less, say 6 GPM? If you're using MP's they are pretty low flow and can cover a good area with them. Also, it's not that expensive to add more zones on a new install. I personally have 11 zones (including 3 flowerbeds) over around 8,000sf running anywhere from 3.5-6 gpm.

I would royally suck to get everything in and realize you don't have the pressure you need, with no easy way to remedy it. You may even be able to use the 40psi heads, which the MP's are designed to operate at. I saw some marks next to the 35 PSI readings, but note that Hunter only has 40 & 30 PSI spray bodies, not 35. Sure you could compensate with a dial at the valve, but then you don't take into account frictional losses between the valve and the spray body.

Something else to consider are the Hunter PGV-100A valves & PGV-101A valves which have flow control (as discussed above). They are 90° valves, but have a lower pressure drop than the straight-thru valves (1 PSI vs 4 PSI). Source: https://www.hunterindustries.com/sites/default/files/BR_PGV_dom.pdf

One last remark is the pressure drop of your back pressure valve. Code here requires RPZ (reduced pressure zone) backflow valves, but I installed a PVB (Pressure Vacuum Breaker) instead. It gave me a few PSI's, but I'll have to swap it before/if I move. It's an added safety that my county is weird about.


----------

