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

With 45 psi, you are almost dead in the water before you begin, if you must employ RPZ backflow protection. One extreme solution to low supply pressure, without employing a booster pump, is to run the main to the property high point, and then use a PVB backflow preventer. Or even use a manifold of antisyphon valves, if you wanted to squeeze an extra psi or two into the system.

And, there are always Maxipaw heads, which function at 25 psi.

I've got to agree with Wet_Boots, RPZ is a killer when you are starting with low pressure to begin with.

The main places to try to recover some of those pressure losses:

#1. See if your local codes will allow you to use something other than an RPZ. I'm not familer with pressure losses of PVBs, but I know the Watts 1" 007 DC has only a 3psi pressure loss (suitable only if you don't plan on ever using a fertilizer injector).

#2. Design for low flow. That will cut down on pressure losses in the main and latterals. 100' of Sch40 1" PVC @ 7gpm has less than 3psi of loss. Two ways to design for low flow... use more circuits and/or use MPRotators. MPRotators are also designed to work as low as 25psi. A lower flow will also reduce other pressure losses. For example (coming from Jess's page) the 5/8" meter should only have 2psi loss at 7gpm.

#3. Tie into the main as close to the meter as possible. That would allow larger pipe for the mains, even if you have to up-size compared to what feeds the house.

OK... HOLD THE PHONE... just had one though that might make all the difference in the world. The spigot where you tested the water pressure... is it before or after any pressure regulator for the house (and are you sure). Most houses are designed such that the water pressure shouldn't be above 50psi. Additionally, the difference between the incomming pressure and the regulated pressure has to be as much as 15psi for some regulators. So if you measured from a spigot that is after the regulator (a typical house will have two spigots, one tied in before the regulator and one tied in after) then it's possible you actually will have more pressure to work with. It might be possible that your real water pressure is something close to 60psi and the regulator for the house is set with an output of 45psi.

Quoted from "OakLawnMDB"

... If there was a pressure regulator, wouldn't it be immediately after the water meter?...

That's what I would think.

My setup is totally different. Water meter is underground at the street. 1" PVC from the meter to just before the house where it transitions to 3/4" copper entering the basement. There is a tee to a "full pressure" spigot, then the pressure regulator, then distribution to water heater and the rest of the house.

Is there a possibility that you could get the water company to install a 2nd meter at the road? Bepending upon various situations, this can be a money saver in the long run as there wouldn't be any sewer fees associated with the 2nd meter (if that makes a difference where you live). That would also cut out that 3/4" line from the road to the house (since you could start at the new meter with 1" pipe).

Sometimes, a pressure regulator can be located right before a meter. In those cases, beware of making alterations, in case the actual street pressure is high enough to do damage. (that isn't always the case)

We need more information. First off, location, which relates to backflow prevention requirements. Property size, so we know the area being watered, now, and in the future. Elevations, as where the house sits on the land.

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.

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.