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TimR

New Member

1

Friday, April 14th 2006, 7:12pm

Advice reworking bad system


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

Wet_Boots

Supreme Member

Posts: 3,882

Location: Metro NYC

2

Saturday, April 15th 2006, 3:00am

Find out what the actual street water pressure is. Maximum sprinkler system performance comes from making a supply connection right after the meter, and before any pressure reducer. If the street pressure is really high, you might need a separate (set at 80 psi) pressure reducer for the sprinkler system. If you're on flat ground, then you could achieve proper backflow protection with antisyphon control valves replacing the existing zone valves.

TimR

New Member

3

Saturday, April 15th 2006, 12:11pm


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.

Wet_Boots

Supreme Member

Posts: 3,882

Location: Metro NYC

4

Sunday, April 16th 2006, 4:34am

This is going to cost you hundreds of dollars to remedy, so don't waste your time looking for shortcuts. If the heads are at a higher elevation than a backflow preventer would be, then you will be using the most expensive type of backflow preventer, the RPZ. You will make a connection at the meter, because that is the one sure way to get maximum water into the sprinkler system, while not touching any of the house plumbing.

As for 'tearing up the yard' goes, simple ecomomics dictate that course of action. An RPZ costs big bucks, and you only want to purchase one of them. That means exiting the house from your new supply connection, with the RPZ installed outside, a good foot or so above grade, and then to the sprinkler system. That also means joining the two separate mainlines of the system. The extra digging is rewarded by not having to spend hundreds of extra dollars to have a second RPZ.

Frankly, the best course of action may be to install a brand new system, and to just cut away the old stuff from your existing hose bibs. Especially as that is the sort of plumbing code violation that can lead to all kinds of grief. Local authorities can actually shut off your water and remove you from your own home, if they see fit do do so. That they have this power, and can exercise it without any hearings in a court of law, is an established fact.

Tom

Supreme Member

5

Sunday, April 16th 2006, 6:16am

20 psi seems very low for house pressure

TimR

New Member

6

Sunday, April 16th 2006, 6:17am


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

Wet_Boots

Supreme Member

Posts: 3,882

Location: Metro NYC

7

Sunday, April 16th 2006, 7:33am

If the backflow preventer is going to be at least a foot higher than any sprinkler head it feeds, then it can be a less expensive Pressure Vacuum Breaker (PVB) - a PVB needs the elevation difference in order to function. With an unfinished basement, just make a new connection at the point just before the pressure reducer. I have been assuming you have the water meter inside the basement, but yours might be outside in a pit. Go ahead and bump up the supply pipe size to one inch. Definitely remove all the existing connections between the hose bibs and the sprinkler system.

TimR

New Member

8

Wednesday, April 19th 2006, 12:23pm


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?


wetyet

New Member

Posts: 6

Location: USA

9

Wednesday, April 19th 2006, 4:41pm

Our county code for backflow protection here in Charlotte is an RPZ type, above ground, cover with the little "door" at the bottom. A licensed plumber pulls the permit and the city inspects from the cross connection to the backflow. Piping sch. 40, 12" deep and 5' copper legs incoming and outgoing of backflow. WHEW!!!!! If I forgot something please don't fine me:)
WetYet? Joe Pell

Wet_Boots

Supreme Member

Posts: 3,882

Location: Metro NYC

10

Wednesday, April 19th 2006, 5:25pm

TimR is probably working to the National Standard Plumbing Code, which requires toxic-rated backflow preventers. Those would include PVBs and RPZs, and without any more local codes/ordinances, the simpler PVB is more trouble-free. Cheaper, too. A PVB at the proper elevation protects against backsiphonage. Backpressure is not an issue in his scenario.

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