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Monday, June 9th 2014, 10:23pm

Little confused on backflow

Reading the guides here and at, I start to think they screwed up when they built this house. Everything seems to talk about backflow prevention as something that's outside the house. In my house, where the water line branches off for the irrigation there is a Watts No. 7 dual check valve (not a double check valve) and I suppose that's meant as the backflow prevention. That is inside the house in a heated space. From there, the line goes outside where there is a shutoff followed by the blow-out connector and then the valve manifold.

This house isn't that old - built in 2005 - and obviously passed inspections. So what gives? From what I'm reading, this is the wrong device in the wrong location. And certainly the wrong elevation because there are sprinkler heads in the front yard a good 10 feet higher in elevation vs this device (and about 14 feet higher than the valves).

So does this just suggest that perhaps backflow prevention isn't all that important in this community (just a thought: is it possible the city provides backflow prevention at the street level??)? Or it was just plain poorly designed/installed and the inspector should have been fired? Or what am I missing? Should I even be worrying about this?

I'm wanting to re-do the sprinklers as I've had a lot of post-winter problems over the last few years (I think the guy blowing out the sprinklers doesn't know what he's doing) and I'm re-landscaping anyway.

FYI. They are NOT anti-siphon valves... I checked that.


Monday, June 9th 2014, 10:44pm

The only reference to backflow prevention that I can find on the city's website is this simple statement:


A Backflow Protection device (Dual Check valve for residential) is required for irrigation connections. A Plumbing Permit is required for the Backflow Protection device.
So I guess that means they feel this valve is good enough.


Supreme Member

Posts: 5,294

Location: Metro NYC


Tuesday, June 10th 2014, 11:45am

You missed the part where you tell us where this property is located. There isn't one universal plumbing code.


Tuesday, June 10th 2014, 12:28pm

Oh yeah. Sorry, meant to write that.

I'm in the District of West Kelowna in British Columbia, Canada.

I actually just got off the phone with one of the city's engineers. She told me it is normal for the dual check valve. Odd thing... she said the reason they don't recommend double check valves is because any valve that CAN be inspected, MUST be inspected... and that's an annual cost to the owner. OK, I get that, but if its the right thing for the job, shouldn't it just be a requirement?

I also discovered that we have 100% of our lines - right from the street's main through the whole house - at 3/4" pex or smaller. Yikes! That's not so good for irrigation, right? No wonder there's so much water hammer.

Are they just being cheap, or this is just the way its done now?

Mostly rhetorical questions. I don't actually expect you to know the intents of our city's planning debt.


Supreme Member

Posts: 5,294

Location: Metro NYC


Tuesday, June 10th 2014, 3:29pm

Almost nowhere in the United States would such a backflow preventer be accepted for lawn sprinkler plumbing. Its common usage is for whole-house protection, often installed right next to the water meter, as a sort of just-in-case safety measure.

The problem with lax codes, is that they can get tightened up later on, and paint a sprinkler system into a corner, needing pressure it doesn't have, in order to overcome the losses from added backflow protection.

You might take a lead from the device-inspection cost that was mentioned to you, and try to design with antisyphon valves. If you properly locate them higher in elevation than the zones they feed, you will have full toxic-rated backflow protection, and not have any inspection fees, since there isn't any way to hook a testing kit to an antisyphon valve. I would recommend an Irritrol 2711APR antisyphon valve, as something you can be sure will be serviceable in future years.


Tuesday, June 10th 2014, 4:25pm

Your statements are consistent with other guides I've read. I find it pretty strange they would have such lax codes in an area where, supposedly, we have the highest quality drinking water in the world. We also have frequent fires to contend with (I know most people hear "Canada" and think snow, but here in the Okanagan Valley, we're actually in Canada's only desert. It is hot and dry here for 8 months of the year). Higher probability of hydrant use + higher than most irrigation frequency = higher probability of back siphonage. You'd expect the codes here to be higher than most, not more lax!

Unless... unless its all part of the overall plan and they handle it on a larger scale at the street level? Not that this helps our own home's water, but it might explain why they're not too concerned about it on a larger scale. She flat out told me NOBODY other than commercial and some much larger older lots use anything other than dual check valves for irrigation.

And it is specifically for the irrigation. It is clearly on that branch line after the meter and AFTER the TEE that goes irrigation/home.

Anyway, I'll investigate the anti-siphon valves. I'm not sure how I'd manage it with our terrain and winter conditions but I'll look carefully at it.



Tuesday, July 1st 2014, 8:02am

Surely you can't think its a good idea to promote your business through blatant spamming? It is obvious that an enclosure isn't a "solution" in this discussion at all. Actually, an enclosure can't be a "solution" for backflow. Are you suggesting that by putting your enclosure on my property prevents backflow? Gee, that was easy.

Post reported. Good luck getting customers with this kind of behavior.


Supreme Member

Posts: 5,294

Location: Metro NYC


Tuesday, July 1st 2014, 8:33am

You could just install one of the "elevation proof" RPZ devices and forget to tell the town you did it. :whistling:


Tuesday, July 1st 2014, 12:46pm

Well, while we're still on this topic...

I appreciate your advice about tightening regs down the road, but I think I'll just deal with it at that time if it ever comes. Unless I'm missing something, I see really zero sense in my using "proper" backflow protection if I know for a fact that nobody else using the system has it. Why spend that money if it is vastly more likely the contamination will come from someone else?

I fully understand that the United States has determined this device is insufficient for the purpose of backflow prevention, but at the same time 100% of the communities in my region of Canada (at least those which publish regulations online) either accept, recommend, or require the use of a dual check valve for "residential irrigation". To date, I don't know of any events of contamination ever happening. Unfortunately, I think that means they're taking the "well let's stick our heads in the sand until it happens" approach, which is just stupid. But it is what it is. What is really stupid is that there's no definition of "residential irrigation". Surely a homeowner could figure it might be a good idea to put a fertilizer injection system on their "residential irrigation" line, right? And the code makes no mention of a higher standard of backflow for this situation, but clearly it would be a bad idea to depend on a dual check valve in that situation. And they know this because when I spoke with the city engineer, she did as me "you're not intending to fertilize with your system are you?". But what if I was and it didn't occur to me to do all this research? I mean, it would be perfectly reasonable to expect a home owner to see the "dual check valve for residential irrigation" and not look into it any further.

The whole thing kinda makes me sick... figuratively speaking (hopefully I don't get sick literally from it down the road).


Supreme Member

Posts: 5,294

Location: Metro NYC


Wednesday, July 2nd 2014, 9:58am

Playing the odds is something the various US regional plumbing codes have dispensed with, and they are correct to do so. Those codes basically declare the entire outdoors to be toxic, and require that it has no possible avenue of entry into a potable water supply. Since toxic backflow is prevented only by those devices rated to do so, that disallows a "dual check" device to serve as sprinkler system backflow protection, as it is rated as effective only against non-toxic backflow.

This "toxic backflow" designation might seem extreme to some people, but employing it creates genuine water-supply protection, and does so in a way that does not require constant vigilance, while also making it possible to confirm that the devices operate correctly (the "dual check" is a piece of brass with a label stuck on it, and you have absolutely no idea whether it functions or not - rest assured the manufacturers did not guarantee it would work perfectly forever and ever)

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