SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

But we've already covered ways to reduce some of those pressure losses.

If you follow Boots' suggestion of designing for a 5GPM system, Jess' instructions indicate the psi pressure loss of the meter drops to 1psi. That will also drop ALL of the flow dependant pressure losses (such as losses in the mainline).

At 5GPM, if you use 1" Sch40 PVC pipe, the pressure losses in the lateral lines will be about 1 psi. (The calculator at Jess' site indicates 100' of 1" Sch40 @ 5gpm only has a loss of 0.66psi.)

So if you redo the design for 5gpm and use 1" pipe:

01psi - Water Meter
11psi - Backflow
01psi - Mainline
02psi - valves
01psi - laterals
25psi - sprinmkler heads
=====
42psi - total loss

That still give you a little breathing room for the valves (which Jess says you should assume 5psi if you don't have specs for the valves you plan to use).

Ok, I don't get how going to PGP or maxipaws would help, dropping the pressure from 30PSI to 25PSI, a re-calculation still shows Total Pressure loss at 49.9 when available pressure is 45PSI, I would still be negative??

Here are the calculations:

Spigot PSI 45
Meter 5/8"
Line 3/4"
Max avail GPM 11 GPM

Pressure Loss Table
4.5 PSI - Water Meter
11 PSI - Backflow RPV
1.4 PSI - House Mainline
2 PSI - Valves
25 PSI - Sprinker Heads
6 PSI - Laterals
49.9 PSI - Total Pressure Loss

regards,
Michael

Quoted from "Wet_Boots"

A separate meter will not increase your pressure.

Sorry if I created any confusion that a 2nd meter could increase pressure.

That could only be the case if, as Wet Boots suggested, there was a city owned regulator before the existing meter. Then I could see a 2nd meter getting installed with either no regulator, or a regulator set to a higher level. Other wise, the ONLY reason to consider a 2nd meter would be if you could get significant savings on sewer rates.

I don't have any experience with Maxipaw or Hunter PGPs, so I can't speak to their operation. But I'm using http://www.mprotator.com and been quite pleased with them. They have various models and all work on only 25psi. The MP2000 will throw 17 feet @ 25psi using only 0.6 gpm for a 180 degree arc (1.2 gpm for a 360 arc). Stretched, that would be enough to water the entire yard on a signal circuit. Divide the yard up into two or three circuits, and the project is sounding doable.

A separate meter will not increase your pressure. You have to figure on losing at least 15 psi through the RPZ and zone valves and sprinkler pipe and fittings. Reduce your design flow, and the losses in the house plumbing will also be reduced. You can do a 1400 sq ft front lawn with 5 gpm, so just plan for running two rotors in a zone. No question that Maxipaw heads will spray further than any gear drive at low pressures, but if you must have gear-drive rotors, you can make Hunter PGPs work in a low pressure design, by using more heads spaced closer together.

HooKooDooKu,

Actually our subdivision is quite old, with a mixture of houses as far as age, our house is about 18 yrs old while others are as old as 50+. We are a Chicago suburb so the winters can be harsh.

The 3/4" water line comes directly from the concrete floor into the water meter. Yesterday, I measured the pressure immediately after the water meter and it was @47 PSI, so no pressure regulator before or after the water meter once the water line gets into the house. I checked with a neighbor and he also found that the PSI is at the same levels.

I guess I will have to check with the water company.

Thanks!

regards,
Michael

Quoted from "OakLawnMDB"

...Another meter and/or line sounds like a lot of extra $$. We live in a residential area, 55FT wide lot, sidewalks, curbs etc. and the current line comes up through the lower level concrete floor. It doesn't sound like a simple or cheap option...

A second water meter may or may not be cheap. If you get one, you would not have it coming to the house and deal with the concrete floor, you would instead have it located out in the yard near the street. The actual cost (to the water company) is pretty minimal. The initial cost might only be a couple hundred dollars. But I've also heard of places where the water company is having a hard time meeting watering demands. In places like that, they might charge $1,000 or more for a water meter because they are trying to discourage additional connections. But the primary issue with trying to justify a 2nd meter is the cost of sewer. Because the 2nd meter would only be used for outside watering, you would pay zero sewer rates for the 2nd meter. That can be a huge savings if you have really high sewer rates. The other thing to factor in is whether there is a minimum monthly charge for the 2nd water meter.

As a personal example, when I looked into a 2nd meter for my house, the initial cost was only about $300. The minimum monthly fee was about $10 (and that pays for something like the 1st 1,000 gallons or something). When I looked at expected water usage and savings in sewer fees, I determined that the system would pay for itself in about 10 years (and would have been a lot sooner if there wasn't the $10 minimum for the winter months when it wouldn't be getting used at all).

Now one thing strikes me as odd from your description. It SOUNDS like this is a relatively new subdivision and that you live in an area where winters are not particularly harsh. If I'm right, it sounds odd that your water meter would be inside the house. I wouldn't think IL is so cold that the meter needs to be indoors to protect it from freezing, and being inside a house seems like more work for the water company when it comes time to read meters. So at the risk of sounding insulting... are you sure thing "thing" in the house is a water meter and not a pressure regulator?

It would be worth following up on Boot's idea of the water company having a regulator installed before the meter. You should be able to contact your water company and ask them what sort of water pressure is expected in your neighborhood, it there a water company installed regulator, if so, can it be adjusted, and if not, can installing a 2nd meter allow you to get more pressure? It's worth at least asking.

Too bad about the RPV ordinance. It does nothing to enhance your safety, unless there are citizens trying to inject fertilizer into the sprinkler water. You can always buy a booster pump to increase the water pressure, but for the money, you can just try to see what you can accomplish with Maxipaw impact heads, which have a low-pressure adjustment built into the heads. 25 psi operation is a certainty, with the standard nozzle, and you might find they can work with a bit less. You might only run two or three at a time, but that's enough to get your lawn watered. Don't skimp on pipe size, and avoiding the usual "funny pipe" swing joints can buy you an extra psi or two.

I found this on Village website:

Reduced Pressure Zone (RPZ) backflow prevention devices will be required on all residential and commercial underground irrigation systems.

Back to work....

regards,
Michael

Be certain of your backflow requirements, because a requirement for an RPZ and nothing else is not something you will often see in codes. On flat ground, a Pressure Vacuum Breaker supplies the same (if not superior) level of protection (high-hazard, or toxic-backflow-rated) that an RPZ does. I say superior, because it functions because of gravity, being that you locate it higher than any pipe or sprinkler that it feeds. In contrast, the RPZ device works because somebody says so. (and we do give credence to what those somebodies say, given what the RPZ costs) I trust gravity more than what anybody says.

If your town has a written ordinance requiring the RPZ, then you don't have a choice. But I would recommend that you ascertain this for yourself, and don't take anyone's word for it.

Also, for just watering a front lawn, another toxic-rated form of backflow protection you might employ is the humble antisyphon valve, using one for each zone. Same elevation requirement as a PVB. The less zones you have, the more attractive an option this is. I do encounter towns that have written ordinances against the use of the antisyphon valve, but this is less about its functional limitation of not running a zone for over 24 hours continuously, than it is for past misuse of a single antisyphon valve 'pretending to be' a whole-system backflow preventer.

Thanks for the input guys!

Another meter and/or line sounds like a lot of extra $$. We live in a residential area, 55FT wide lot, sidewalks, curbs etc. and the current line comes up through the lower level concrete floor. It doesn't sound like a simple or cheap option.

I live in Oak Lawn, IL and a RPV is required by the village. I will be watering the front yard @1400 sq/ft, level ground no elevations. The 3/4" cooper feed from the street comes up through the concrete floor of the lower level of a split level, directly to the water meter.

I will be breaking into the 3/4" copper line coming out after the water meter this afternoon, I will check the PSI at that point.

regards,
Michael