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

Hi:

What type of backflow device are you using? Most important part of your system.

Why not put the EZ flow on a "U" loop, so it can be valved off. The EZ flow is connected at the bottom of the "U" and each side of the U have a Ball valve on it. The main line crosses at the top of the U, and has a ball valve between the arms of the "U". Your valves on the uprights of the "U" are only open when using the "injector". And, unless you are using the injector, the valve betwen the top of the "U's" upright stays ope (on the main line).

Many venturi type "injectors/infusers" conmsiderably restrict flow and pressure. With the "U" suystem, you only induce these restrictions while fertigating. Prevents wear and tear.

I generally "T" off a valve (hose bib) for pressure checks and winterization.

Consider filtration if using drip. High volume screen filters are inexpensive, effeective, and prevent a host of problems.



Jeff

Thanks, and you understand the "U" I was talking about. I thought the system worked better at high flow rates (I'm mostly a drip kinda guy), and a valve on the mainline would be necessary? I have installed and use them this way. I am nowe mostly working with injectors, so may be wrong about the EZ flow. I have an EZ flow, and found it works better (relatively) with a direct line thru its "coupler". That is why I suggested the ball valve on the mainline between the "U" uprights.

I would think, using the "U" with valves would protect the coupler during backflow, or blow-out.

I connected the bottom of the "U": using quick connects, so I could disconnect in winter, and to move to other systems. I still use the quick connects on the "U" with my injector. Easy to take in in winter.

I thought part of your question regarded protecting the coupler during winterization, and blow-out

What type of backflow are you using?? This is the most important part of your system.

Thanks for the "U" diagram. Good job. I'm Not an autocad user, mostly photoshop.

Jeff

The microsoft Visio looks neat. I'll try it this winter when we are out of season.

PVB is the best cheap backflow prevention for what you are doing It is probably much better than DCA's which we use here in Washington, and what I used in Texas.

However: Both are inadequate. The reduce pressure DCA is the only bF preventer cleared for use with fertigation. I know, no one wants to hear that. The system we worked out is better than leaving the infuser connected all the time. BTW, I saw a 3/4 inch PRDCA at Lowes for $115. Probably old stock, or a close out. I should have jumped on it.

Over and out: Jeff

PVBs are going to be fine if the only thing you were doing was irrigation.

But the key here is that with fertigation, you are injecting something into the water. Any time you do that, any where in the country, you are required to you an RPZ (for personal liability, if not by law). Jusme, I think Jeff's description has confused you. There are basically three types of backflow (ignoring antisiphon valves). These are PVB, DCA, and RPZ. Now an RPZ and a DCA are mechanically nearly identical (both contain duel check valve assymblies). But an RPZ is designed in a special way that it attempts to maintain a pressure drop (of about 10psi) between the two check valves. If for any reason this pressure drop can not be maintained, the RPZ begins dumping water out of a discharge located between the two check valves. The idea is that even if something fouls the check valves and they get stuck open, the RPZ will no longer be able to maintain the pressure drop and water will get discharged rather than being allowed to backflow.

Jeff used the description "reduced pressure DCA", and that equates to RPZ, which stands for Reduced Pressure Zone. In other words, an RPZ is a DCA with a reduced pressure zone, and that takes the device to a whole new level, a level of protection that is REQUIRED when ever you are adding something to the water.

Basically, by taking it upon yourself to put something in the water, you have to increase your level of protection from backflow. When it comes to simple irrigation, the typical source of contamination is stuff put on the lawn that gets possibly sucked back in the pipes. That contamination has to then work its way back through the system to ever foul up the water supply. In the area of simple irrigation, most building codes realize there is only a small risk of this type of contamination making it's way all the way back to the water supply, and therefore only a PVB (or DCA where allowed) is all that is needed to reasonably maintain the safety of the water supply. But you are adding a contaminate directly to the water supply. That has a relatively HIGH probability of contaminating the water supply, and therefore you have to insure that backflow can not happen. For this situation, a DCA is completely inadequate as all that is required for contamination is something cause the check valves to get stuck open and a loss of system pressure to have your fertigation begin contaminating the water supply. I'm not as familiar with the exact workings of the PVB, but again, they still have a serious potential of allowing backflow under some condition. The RPZ, on the other hand, is designed with basically a fail-safe system. Even if something causes the RPZ to essentially fail, the RPZ aspect comes into play and continues to protect the water supply.

So bottom line, if you are injecting something into the water supply (in this case, you are adding fertilizer), then you MUST protect the water supply with an RPZ. An RPZ is going to be the most expensive option (and it should be since it offers the most protection). It is also a device that MUST be installed above ground (the fail safe design will also fail if the device becomes submerged, so it can't be located where it will get drown when the fail-safe kicks in and starts spewing water).

So if you want to use a PVB, then you will need to abandon the fertigation.

As for your drawing, I'd like to offer a suggested modification. Place the shut off valves leading to the Ez-Flo ABOVE the unions rather than below them. That way, you can remove the fertilization device at the unions for repairs/maintenance, yet sill use the irrigation system by simply closing the valves.

As for the order of installation, I don't think it maters so long as the design allows the fertigation device to be removed for winterization (hence another reason to have shut off valves in the U ABOVE the unions) and the drain is located at the lowest point (keeping in mind that you've allow some path for the water between the blowout and the backflow to drain out after winterization).

AMEN ! And Washington State. Check out injectors...Dosmatic, etc. Jeff