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The last 10 posts

Friday, August 15th 2008, 3:36pm

by Lowvolumejeff

great

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

Friday, August 15th 2008, 2:11pm

by jusme

Thanks for the help and info guys. I had read on the Ez Flo and Fertigation sites that an RPZ or PVB would be the best type of protection against backflow for a fertigation system, but I know you guys are right. I'll swing by Lowes and see if I can find a reasonably priced RPZ or maybe Ewing. I was just trying to be cheap but 1.) it doesn't make sense to pinch pennies when it comes to safety, and 2.) it would cost me more in the long run if I failed an inspection. I don't think they perform inspections around here but for both of those reasons it's always better safe than sorry.

Friday, August 15th 2008, 8:48am

by HooKooDooKu

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).

Thursday, August 14th 2008, 6:56pm

by jusme

When you say Washington, do you mean the state or the capitol? I live in Washington State so if that's where you mean I'd like to know why you favor DCAs over PVBs, aside from the concerns over cross-contamination with fertigation. I am actually considering installing a DCA instead just so I don't have this ugly thing on the outside of my house and compared to the overall cost of the system so far it's really not much of a relative price different between a PVB and DCA.

I think I'll definitely have to check stock at Lowe's next time I head there and see if I can get something for a reasonable price. If not, and if you are referring to Washington State, do you know specifically that PVBs are not approved to use with fertigation? Or not approved at all?

I checked a bunch of legislation on cross-contamination for Washington State and it all points back to a state law that approves PVBs amongst other backflow preventers. I'm guessing that local law or water company regulations can supercede state law so I also called my water company and asked about approved backflow preventers. I spoke with two people there and they both didn't seem to care about what I was asking and basically said, "Eh, use whatever you want for backflow prevention, it should be fine." I thought that was pretty strange considering some states and municipalities are so strict.

Thursday, August 14th 2008, 6:43pm

by Lowvolumejeff

Backflow

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

Thursday, August 14th 2008, 2:14pm

by jusme

Now I think I completely understand what you're talking about. I updated the drawing slightly to show the "bypass" ball valve on the mainline. The more I think about this design the more I like it too. I'm not particularly worried about being able to easily remove the EZ Flo coupler. The unit's hoses can disconnect from the coupler pretty easy to bring the unit itself inside for winter. This design, with being able to completely bypass the coupler, seems like it's very well tailored to winterizing. The only thing I would consider adding is perhaps another drain at the bottom of the U because that would undoubtedly be the low spot in my mainline so that I could ensure no water stayed in there after draining. Or your idea of being able to disconnect the bottom of the U entirely would work too, I'm just worried about how robust these quick connects are that you mentioned. I wouldn't want them to blow off or anything.

I decided to go with a PVB for backflow prevention because it was the cheapest option that seems to be an acceptable form of backflow prevention. On one hand I wish I had paid a little more and got a DC so I could put it underground in a box and out of view, but on the other hand I saved some cash by buying a PVB.

(I actually used Microsoft Visio to design my system and issue those drawings. It works admirably well lightweight CAD and has some other useful features as well like Reporting which will generare a report of how many of each fitting (for example) you have in the design. This basically generates a parts list for me and if I put which valve each fitting belongs to then it also essentially creates a build plan. Pretty cool I think.)

Thursday, August 14th 2008, 1:52pm

by Lowvolumejeff

Thanks for the picture

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

Thursday, August 14th 2008, 12:14pm

by jusme

I'll think about using the U-type bypass you mentioned but the EZ Flo already has in/out shut-off valves on it. In a standard installation water will always flow through the coupler but I don't see this restricting flow or causing much pressure loss if the unit is "off" (shut-off valves are closed).

(Edited to add: Is this the type of design you're talking about? Click for larger version.)



My main question is still what is the most logical order to put these items in? Does anyone see any issue with EZ Flo, then stop & waste valve, then the quick coupler?

Thursday, August 14th 2008, 11:50am

by Lowvolumejeff

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

Thursday, August 14th 2008, 11:00am

by jusme

Placement of drain valve, quick coupler, and Ez-Flo fertilizer system

Hi all,

I have three items that will be installed between my backflow preventer and the valves:

  • A manual drain valve (probably Stop & Waste) to release pressure in the mainline for repairs/winterization
  • A quick coupler for winterization
  • An Ez-Flo system
In which order (from upstream to downstream, aka flow direction) would you put these? I'm thinking that it probably doesn't matter but if anyone has a strong opinion I'd like to hear it. I guess my only worry is blowing out during winterization through the coupler for the Ez-Flo system. I don't want to damage that special coupler and have to find a new one somewhere. Perhaps it makes the most sense to have it in this order? 1.) Ez-Flo, 2.) Stop and Waste valve, 3.) Quick coupler. My thinking is that during blowing out I can leave the Stop and Waste valve closed to prevent blowing backwards (upstream) through the Ez-Flo coupler. Any thoughts?