Backflow preventer for yard hydrant?


  #1  
Old 05-11-15, 07:13 PM
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Backflow preventer for yard hydrant?

Hi,

I have a frost-proof yard hydrant near my well. I'm assuming it's teed off the line to the house, as I've seen no evidence of any pipe going from the house out to the yard.

Recently, the county tested the water and it was quite high for coliform, so the system needs disinfected.

The water guy at the county said that one way the well can get contaminated is from the frost-proof hydrant. He said new installations are required to have a backflow preventer between the hydrant and its tee to the main line into the house.

Question:

A web search shows many different kinds of backflow preventers. Could someone please provide a link to an example of the kind I need?

Thank you!
 
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Old 05-12-15, 04:58 AM
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Any Lowes or Home Depot has them in the garden department that just screw right on the garden hose fitting.
 
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Old 05-12-15, 05:47 AM
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I know a back flow preventer is required but it's a really long shot that the hydrant is the source of contamination. The water piping is pressurized so the flow is outward even if there is a leak. For the hydrant to contaminate the well the well pump would have to be turned off, the water piping bled of water pressure, the foot valve at the bottom of the well needs to fail and a hose full of water needs to be connected to they hydrant so water can siphon back into the well. You can put a back flow preventer on but I don't think it's going to make a difference in your water quality.
 
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Old 05-12-15, 05:51 AM
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My understanding of a frost-proof hydrant is that after each use, water in the standpipe drains into the ground.

While the screw-on type prevents contamination from the point of the garden hose connection outward, it will not protect against contamination from the point in the ground where the water drains from the standpipe.

That's the way I understand it - does it actually work differently than that?
 
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Old 05-13-15, 02:50 PM
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Thanks, Pilot Dane.

The installation is at my weekend home. I shut off the power to the pump when I'm not there and this past year I've not been there much. Plus, the system was open twice in the past 18 months - once to have the pressure tank replaced and once to have a broken (frozen) pipe replaced.

For the hydrant to contaminate the well the well pump would have to be turned off, the water piping bled of water pressure, the foot valve at the bottom of the well needs to fail and a hose full of water needs to be connected to they hydrant so water can siphon back into the well
Could contamination get in from the hydrant drain also? (see previous post)

In case I decided to get a backflow preventer, could you please provide a link to an example of the kind I need? (I'm aware of the screw-on type, but I'm not sure that is actually what I would need - see previous post)

Thank you - I appreciate all your help.
 
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Old 05-13-15, 05:03 PM
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If you do have a frost proof hydrant then yes, the water does (or at least should) drain down out of the hydrant when you turn it off. If you install a screw on type it would only prevent water from an attached hose being sucked back down. A frost proof hydrant should drain itself so there would be nothing for a backflow preventer to prevent but if you do want to install one on the hydrant it would have to be underground between the water line and hydrant and in your climate it's probably 3 or 4 feet down. Another option would be to install one on the main water line coming out of the well. That would prevent water from anywhere in the system from flowing back down into the well.

Now that I've typed all that... it's all well and good in a system that gets used frequently. In a system that sits for months between uses I'd be leery of installing anything. When water is not flowing the bits in a check valve or backflow preventer may tend to stick or leak.

Personally I'd get in the habit of shocking the well and water pipes when first going to the cabin or just drinking bottled or boiled water considering how infrequently you use the cabin. You have not identified the source of the contamination so installing a backflow preventer may not help. And coliform is not something you often find in a garden hose. I'd be looking for ground water contaminating the well. A cracked well pad or casing or a racoon pooping in the well.
 
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Old 05-13-15, 05:38 PM
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In a system that sits for months between uses I'd be leery of installing anything. When water is not flowing the bits in a check valve or backflow preventer may tend to stick or leak.

Personally I'd get in the habit of shocking the well and water pipes when first going to the cabin or just drinking bottled or boiled water considering how infrequently you use the cabin.
I apologize if my wording was misleading. Normally I go there two or three times a month. It's just been this past year that it's been less frequently - as in once a month.

1) I plan on getting there more frequently aqain (like two or three times a month). Would that change your recommendations regarding the backflow preventer or shocking the system?

2) I mention that the system was open (i.e. partially drained) twice within the last 18 months thinking that that may have been opportunities for infection. Does that sound plausible?

I appreciate your help and detailed response above - that helps me understand the situation better.

Thank you much!
 
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Old 05-14-15, 08:01 AM
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It's extremely difficult to contaminate a well via the piping backflowing. It can happen but 99.9% of the time the piping contains water that came from the well so it's just the same water going back in. The contamination is more likely coming ground water entering the well somehow which unfortunately is a much more difficult problem to fix.

If it was a one time contamination then shocking the well and your pipes with chlorine will take care of it. You could also test that theory by shocking the well and not using the lawn hydrant and see if the contamination returns. If it's a physical problem with the well or contaminated water source then you'll need a new well or a water treatment system to sanitize the water if you want to drink it from the tap. For a cabin I would consider useing boiled or bottled water for drinking and cooking because of the cost of a new well or a treatment system.

How old is your well and what is it's condition? What type of well is it (spring, drilled, dug...)? What is the area around your well like?
 
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Old 05-14-15, 08:48 PM
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How old is your well and what is it's condition? What type of well is it (spring, drilled, dug...)? What is the area around your well like?
Drilled 1990, depth 85 feet, 6-inch galvanized casing. Top 12 inches is clay soil, remainder limestone bedrock. Casing extends 20" above grade.

The well is in our back yard, near the transition from open lawn to wooded lawn area and natural wooded area. The well head is near the top of a gentle slope (as opposed to being in an area subject to significant runoff).

The nearest crops are 300 feet and there is no livestock within 1/2 mile.
 
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Old 05-15-15, 01:12 PM
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I would shock the well and piping properly then have the well re-tested in a month or two. If it was a one time contamination the test should come back good. In the interim drink bottled or boiled water just to be safe.

If you think of where coliform comes from it's very difficult for it to enter the well via a yard hydrant or anything on the potable water side. More common would be bad luck and a leaking or rusted out well casing letting surface water, possibly from a septic system, contaminate the well.
 
 

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