What would happen if I just bypassed this garden water check valve?

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This garden Wilkins Zurn water check valve is leaking: SMALL:
LARGE:

I can't understand HOW it works given that it's at the top of a hill.
At that height above the house, no water is ever going to flow backward into the water supply (I think).
The only water higher is the water tank itself, the bottom of which is at the same level as this Wilkins Zurn water check valve.
I don't know WHY this check valve even exists, since it's 10 to 20 feet ABOVE almos all the spigots (except those at the water tank itself).
Do you agree I can just bypass this check valve? Or am I missing something obvious?
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On 11-05-2012 20:16, Danny D. wrote:

You have water higher and you expect it to ignore an opportunity to get lower?
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Wes Groleau

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On Mon, 05 Nov 2012 22:25:37 -0500, Wes Groleau wrote:

Hmmm... the water goes lower all the time.
Otherwise, I'd have no water in my garden hoses.
It's the OPPOSITE direction that the check valve is for.
However, I can't imagine water ever climbing that high UP from the garden hose into the water tanks on the other side of the check valve.
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On 11-06-2012 00:33, Danny D. wrote:

Sorry, when you said "the only water higher" I thought you meant there actually was some water higher..
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Yes, you are missing something obvious. If there is no check valve there, water can be drawn by vacuum back into the house. The elevation of the line is immaterial.
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On Mon, 05 Nov 2012 20:40:55 -0700, Robert Neville wrote:

Hmmm... that must be true because they bothered to put the check valve there.
Are you saying ALL houses which have a separate line for garden hoses than for the house, have a check valve ONLY on the garden hose line but not for the house?
Because I have only one check valve ... and it's ONLY for the garden hoses.
The way I know that is I shut it off (because it was leaking), and only the garden hoses stopped working.
So, is EVERYBODY's house designed this way?
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On Tue, 6 Nov 2012 01:16:11 +0000 (UTC), "Danny D."

Backflow preventers are often required by code. If it is in your town, removing it is a violation.
do you really need it? Probably not for most people. What they do though, is prevent backflow or siphoning if you pressure drops. In the case of a line with lawn sprinklers, it prevents backflow of lawn fertilizer and dog crap to the drinking water system.
Most times they are needed in industrial or commercial applications. In the case of a pressure drop, a boiler or water tank could easily force water back into the system. Residential use, possibility is much less. But I'm not going to tell you to take it out. They can be rebuilt too.
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On Mon, 05 Nov 2012 22:42:01 -0500, Ed Pawlowski wrote:

I've never seen one of these before on a house. Certainly if they were in my old house, I didn't see them.
This new house (new to me anyway) has this 'backflow preventer' only in the line that goes to the exterior hoses and sprinkler system.
So what you said makes sense. It's to prevent the sprinkler system from being sucked back into the water supply.
So, I guess it's needed.
So I'll look up how to rebuild it then.
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Danny D. wrote:

It is the code where I live. I do't want to have even one in a thousand chance of drinking dirty water no matter what. I have them on outside faucets and in-line feeding sprinkler system.
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On Mon, 05 Nov 2012 21:58:22 -0700, Tony Hwang wrote:

Yes. That's what it's on for me too.
It's only at the top of the hill, at the level of the bottom of the water tanks, and it's ONLY for the sprinkler system and hoses that are OUTSIDE the house.
The spigots on the house seem to be fed by the home water system, which is a separate pipe.
Someone said I could rebuild it - so I'm going to Home Depot tomorrow (and maybe Lowes) to find the parts to rebuild it if I can.
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Danny D. wrote:

Jeez, just buy a new one.
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dadiOH
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On Tue, 06 Nov 2012 07:30:05 -0500, dadiOH wrote:

That's probably not a bad idea.
I'm trying to figure out what it is so I can price it. And how it works.
For example, what's the purpose of the four female fittings?

BTW, I found the Wilkins Zurn backflow checkvalve page: http://www.zurn.com/Pages/Search.aspx?k ckflow&akckflow
But I haven't yet found the particular device to obtain price and availability and instructions as to what those four fittings are for.
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There are some curious fittings on many of these backflow preventers. I had a sprinkler guy install a new system and he said they are for testing purposes and someday some code official might want to use them for testing, but he'd never seen it done.
I would not get hung up on that aspect. If you're really concerned, find what you think is a suitable replacement, regardless of the fancy fittings, print out the datasheet and take it to your local plumbing inspector and ask. That's the only way you'll know for sure, regardless of what anyone here thinks.
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On Tue, 06 Nov 2012 06:59:55 -0800, snipped-for-privacy@optonline.net wrote:

I called up Wilkins Zurn (Wilkins Water Works) technical support. They told me those four fittings are for testing purposes, as you had surmised.
I'm reading all I can on it from the datasheets right now since it's a $755 part with a $55 repair kit - but, as you know, repairing (fixing) takes more effort than simple replacement.
Wilkins Zurn 975XL Specification Sheet http://content.zurn.com/web_documents/pdfs/specsheets/BF-975XL (lg).pdf
Wilkins Zurn 975XL Maintenance Sheet http://content.zurn.com/web_documents/pdfs/installation/ISSM950.pdf
I wonder if there is Linux freeware for these CAD drawings? Wilkins Zurn 975XL CAD drawings (DXL) http://content.zurn.com/web_documents/dxf/975XL.dxf
Wilkins Zurn 975XL BIM 3d Model http://tinyurl.com/aj8fh26
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SNIP
.

A swing check is not a suitable replacement for a vacuum based back flow preventer.
As Ed has mentioned it is difficult to know if the installation under discussion "really needs" a backflow preventer but often it's a local code requirement.
I have / had a similar situation. The back flow preventer (Wilkins/ Zurn) suffered a hard freeze, the unit started to leak. Someone (who shall remain nameless) volunteered to "take care of it" for a very small fee since I was too busy to attend to it.
My wife had the guy "take care of it"... His solution? A $15 swing check valve.
The result? Fast forward a couple years... the city is now sending out letters requesting the mfr name & unit serial numbers of backflow preventers. You see, backflow preventers are such sophisticated devices that they are serialized.
Those "female fittings" on the side are mini 1/4 turn valves that are used to test the unit's functionality. In some installations, formal testing at specified intervals is required.
For OP & anyone else who to learn about backflow preventers I offer...
http://content.zurn.com/web_documents/pdfs/installation/ISSM950.pdf
OP-
The link also has troubleshooting info as well.
Ebay is a possible source of reasonably prices units.
cheers Bob
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Standard drawing exchange format. On Linux, insert into LibreOffice Draw, Draftsight, maybe QCAD, GIMP.
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On Tue, 06 Nov 2012 12:24:25 -0800, Oren wrote:

Interesting!
Unfortunately, I already ordered the $45 repair kit - but if an entire NEW 1" (ID) check valve is only a few dollars more, then I goofed!
I should have asked sooner.
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As others have said, a backflow preventer is not just a check valve.
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My guess on those four female fittings is one of two things: 1. you could run four above ground water lines to different zones in your yard or garden. It looks like they have quarter turn shutoffs for each one.
2. they may be for blowing out the system with an air compressor, but being that there's four of them and the height location in relation to the yard, this is doubtful. On my underground lawn sprinkler system, I have to blow mine out prior to winter so that the water in the lines don't freeze and bust the pipes.
I agree with the prior posts that the backflow preventer is necessary.
2.
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