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

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by wetyet</i>
<br />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.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Every location has different codes. That would be an example of one of the most restrictive.

My city (currently) is almost the exact opposite. I called the city building inspector before starting my irrigation systme and was informed that the only requirement is that some sort of backflow be installed. Beyond that, the SUGGESTED that a licensed plumber make the initial connection to your water main. But otherwise, no permits or inspections of any sort are needed.

When I went to start installing my irrigation system, I called the city inspector and was informed that currently no permit is required and that some sort of backflow prevention be installed

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by TimR</i>
In reading through info on PVBs, everything mentions that they only protect against backsiphonage and that they are not acceptable protection against backpressure.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

That's why it's required that the PVB be located higher than ANY of the spray heads. With all the rest of the irrigation plumbing downhill from the PVB, gravity can't create backpressure.

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.

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

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?

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.

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

20 psi seems very low for house pressure

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.

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.