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

Hi, and welcome to the forum. No question is too easy, but many are hard, mostly because we can not visualize it. That said, please remember my advise is without seeing it, and may be incorrect based on teh actual circumstances. Also, things here are read by others, and they must understand these limitations.

Luckily, you don't have a large area. If it was a larger lot, I would be recommending a new meter, one dedicated to your irrigation needs, and sans sewer costs. In your case, the small area needing irrigation does not warrant this. You did not specify how much of this aa is turf, vrs. beds. If it is mostly beds, drip is the best option, and write back for suggestions. For this discussion, I am assuming mostly turf.

Disclaimers done.

Your second post probably has the best option. I suspect your hose bibs are supplied by 1/2 (copper or PVC). Your velocities thru 1/2 schedule 40 PVC must not exceed 4.22 ft/sec, or 4 GPM. I know they now give you more, but they are not flowing at maximum rate to a distant valve. If the supply to your 1/2 in faucet is 3/4 PVC (all calculations based on schedule 40), the maximum velocity is 4.81 GPM. Exceed these velocities, and you will have waterhammer to deal with. You will also probably experience some internal plumming water flowing noise in the house so be aware of that if your home contains light sleepers.

So the best option is going for the 3/4 tap and run he PVC around the house. Your still should not exceed the 4.81 GPM velocity.since it is going thru the house. You mayexperience an increased pressure. Best to test it after you make the tap. Again, do not exceed the 4.81 GPM recommondation !

Since you have a relatively short distance to run the PVC to yor manifold, 3/4 inch will suffice. Over 100 feet of 3/4 PVC at the permissable velocity you only loose about 5 PSI. You are going 50 feet, so it is about - 2 1/2 PSI.

So your loss to the manifold counting fixtures, will be less than 3 PSI. Increase the velocity (more GPM) and those pressure loss number increase and you would consider up sizing your pipe for longer runs, with higher flow.

Now, with only 4 GPM, your choice of heads is limited, unless you want to have a lot of zones = more $). Again, the lot dimensions are not specified, but its relatively small size lends ne to believe pop up sprayheads might be your best choice. I suggest you strongly take a look at MP rotors, which perform very well, are adjustable, require low GPM flow, fit on numerous heads (including my favorite the Rainbird 1804), more efficient than sprays (larger water droplet = less loss to evaporayion and wind drift) and are fun to watch work. You will be able to put more heads on a zone, saving by not installing more valves,pipe, wire, and a bigger controller. All, and Weatermatic Valves are available from this sites sponser at a good price (www.sprinklerwarehouse.com). I recommend them and receive no consideration for the endorsement. Recommend Weathermatic silver bullet valves with flow control. Work well at low flow rates, and are easy to clean if necessary. Also have internal manual bleed, so when turning system on manually, your valve box doesn't flood with water.

So, KIS, go with 3/4 inch throughout (saves money on fixtures if uniform size throughout), Weathermatic valves, 1804's, with MP rotors. And, did I mention MP Rotors?

Good luck, and if my assumptions are wrong, write back for more. Jeff

Very small lawns can also be watered from a hose bib, so see what you might obtain there.

Quoted from "SSASMITTY"

...I have a drop ceiling in the bathroom so I could possibly hide the pipe up there until it enters the garage. Are there issues with exposed pipe in a garage?...can I put the backflow device in the garage?...

To my knowledge (as a homeowner), there are not any issues with exposed pipes so long as it is copper (metal). Anywhere you use PVC (Sch40) on a mainline (pipe under constant pressure) , it must be buried.

While legally, I believe you can install a PVB or RPZ in a basement/garage (so long as it's impossible for the device to become submerged). But because of their constant potential to spew water, it's never recommended. So for all practical purposes, the only backflow device you could install in a basement is a Duel-Check backflow device. Under normal operation, they never leak water, but you do have to have the test cocks accessible. However, DCs are considered not as safe as PVB and RPZ and therefore may not be permitted by local codes. (Note: DCs are always inappropriate if something is being added to the water such as fertigation.)

Since you have a small area, you could use the pipes leading to the existing hose bibb in combination with MP-Rotators. A square 700sqft area could be watered with a set of MP3000, one in each corner, and require less than 4gph. Break it up into two zones, and the hose bibb should be more than enough for a 700sqft area using MP-Rotators. Since irrigation is usually run in the mornings before sun-rise, I too was warned about the noise an irrigation system can cause when the water path includes flowing through the house. That is part of the reason I tied into my water main in the yard before it comes into the house (meter is at the curb). At a miniumum, you'll likely want to avoid the water either running through a wall that includes a bedroom on the other size, or running through pipe hung from a ceiling that is also the floor of a bedroom.

Quoted from "ssasmitty"

Jeff,

Thanks for the response, it was extremely helpful. Don't know how much this matters, but the 3/4 line I want to tap into is copper. How much does this change the numbers? I have no problem spending the extra $$ to run 1" mainline if that will help. Dimensions for the yard is 30'x20 with another small section between the road and sidewalk. Thanks again.

Jason

3/4 inch copper is better than 1/2 inch copper. In 3/4 Copper maximum water velocity = 4.42 GPM. Ideally, your question as to pipe size requires knowing the dynamic pressure (working pressure) at the POC. This would assure the proper design to allow adequate presure at the most distant head to determine it's coverage. From this point on, you loose pressure at the BFD (4# for a DCA), the piping, the valves (about 3 - 4 PSI for Rainbird, only 1.2 PSI loss in Weathermatic Silver bullet - 12000series), and the fittings. Although 3/4 inch is probabbly more than adequate, but since you are using so little the cost of upsizing to 1 inch is minimal. Go for It. Cost difference going to 1 inch is less than $20, and you won't ever have to second guess your decision. Again, I think 3/4 is adequate, but in irrigation the mantra is "Bigger is Better".

MP Rotors work very well between 30 and 60 PSI, although their coverage is slightly diffent at the different pressures. Your pressures thru-out the zones will be roughly equal. Research them, and check out your plan here.Seems like triangular spacing might work on the 20 X 30 (MP 1000 at 50 psi cover about 14 feet). Read about head placement at www.sprinklertutorials.com

I'll venture that if I understand your design and layout of piping thru the house, at flows less than 4 GPM will greatly decrease any water flow noise you hear by piping into the copper outside the garage.

Let me know how it works out. Jeff