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

I’m looking for some advice on how to improve a sprinkler system that I inherited from the previous home owner.

This is the order of how the system is setup:
Water main enters the house through the floor of the basement.
Ball Valve (for cutting off water to house).
Pressure reducing valve.
House plumbing transitions to 3/4" CPVC.
Tee transitions to 1/2" CPVC.
1/2" CPVC attaches to front hose bibb on outside of house.
Hose bibb vacuum breaker.
(Everything above this was from the original house construction. Below is the actual sprinkler system construction.)
3/4" PVC attaches to vacuum breaker.
"Replacement" hose bibb installed on PVC tee.
Other end of tee runs to a ball valve (for cutting off sprinkler system).
PVC drops underground and runs to zone control valves.

In addition, the system is also attached (in the same way) to the rear hose bibb. So, by opening the front and rear sprinkler cutoff valves it is possible to run water from the front hose bibb through the system all the way to the rear hose bibb.

Pressure reads 20 psi at the "replacement" front hose bibb and about 19 psi at the rear bibb.

There are only a few sprinklers in each zone so the system actually works, although it seems pretty marginal.

Most of all I don't like that there isn't a real backflow preventer installed. I suspect putting one on the current system would drop it from marginal to inoperative. So, I'm thinking that I should tee off the 3/4" CPVC in the basement to a new 3/4" (or perhaps 1"?) supply line. Run that outside to a backflow preventer. And then attach that into the existing sprinkler system 3/4" line. Then completely disconnect the system from both the front and rear bibbs. I could tee off the house water supply before the pressure reducer, but I'm leery of putting too much pressure in the system.

It's likely that I'll only be in the house for another year or two, so I'm not really interested in completely redoing the system. On the other hand, leaving it “as is” isn’t an option either in that I couldn’t in good conscience leave this safety hazard for the next owner.

Ideally I'd like to end up with more pressure/flow than I currently have so that there isn't any question about the sprinklers working consistently. Any opinions if this plan will accomplish that or recommendations for a better plan?

-Tim

Considering this issue some more this morning, I realized the flaw in my thinking ... Increasing the pipe diameter by replacing the 1/2" CPVC with something larger is only going to increase my flow rate, not the pressure (correct?).

Does 20 psi seem reasonable for my house pressure?

Is there a simple way to determine the street water pressure? Can the county tell me? My neighborhood had a sprinkler system installed in one of the common areas just last year. I was looking it over to see how it was installed (it has a Wilkins 975XL backflow preventer) and hooked up my pressure gauge to the hose bibb. It read 70 psi. I'm not positive if the bibb was before or after the backflow preventer, I'll try to look it over again. I didn't see anything that might be a pressure reducer though (unless it was buried w/o an access box). Is 70 psi likely to be the street pressure then?

I understand that making the connection right after the meter would be ideal (thanks to all of the forum posts), but this would involve tearing up a lot of my yard. Since I'm not looking for a drastic improvement in pressure will making the connection in my basement just before the pressure reducer (Wilkins Model 70) be adequate?

Yard isn't flat at all. In addition the existing control valves are spaced around the yard (most in the middle of the grassy areas), so it seems anti-syphon valves are out.

Thanks for the help.

Yard slopes up from the street to the front of the house and then down from the front of the house to the backyard (basement is walkout in the back).

So for the backflow preventer to be higher than all of the heads it will need to be installed roughly in the area where the front hose bibb is. Seems like this would be a good location anyway since it's up against the house and in a flower bed so it wouldn't be in the way.

So I either connect at the meter and run the new pipe up to the house and to the backflow preventer (your recommendation in the last post) or I connect in the basement where the main comes into the house (before the pressure reducer). Basement is unfinished, so doing the work there is pretty simple.

Where does the pressure reduction come from between the meter and where the main enters the house? Is this typically just too small of a pipe diameter? Or are there more pressure reducers in the line?

The current two mainlines to the system are already joined. So I can just remove the connection from the rear hose bibb and cap it below ground.

I really appreciate all of the help Wet_Boots, not trying to be difficult, just want to make sure I am presenting the situation correctly.

-Tim

Yes, meter is outside, in a pit near the street. Getting good elevation shouldn't be a problem, so looks like a PVB will work.

In reading through info on PVBs, everything mentions that they only protect against backsiphonage and that they are not acceptable protection against backpressure. Do I need to be concerned about this? Or is this not an issue since I don't have any kind of booster pumps in my system and everything downstream is at a lower elevation?