Need to stop sprinkler system from siphoning from water treatment

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by sp00kster, Mar 15, 2006.

  1. sp00kster

    sp00kster New Member

    Messages:
    15
    I am not sure if this is proper forum but any help greatly appreciated - Quick version

    We are on a well - sprinkler system is the first plumbed outlet after pressure tank then on to water treatment system (chlorination). Problem I am having is that the sprinkler system when on is siphoning from the water treatment system. Basically watering the yard with heavily treated water. I installed a spring type double check valve as well as a pressure gauge for monitoring and regardless my efforts it still continues to siphon through the check valve especially on high volume stations. All fittings are brass 1" NPT.

    I was looking at perhaps back flow preventers (guessing) - but there are many styles and do not wish to purchase wrong valve

    Any help in this matter would be greatly appreciated
  2. dubldare

    dubldare Plumber/Gasfitter

    Messages:
    286
    Location:
    MN/ND
    First, make sure you have a pressure vacuum breaker installed where the irrigation feed leaves the house, prior to the connection to the sprinkler system. The critical-level (CL) of the vacuum breaker must be at least 12" above the highest point of irrigation piping. If this cannot be done (due to elevation), an RPZ is required. This protects your drinking water.

    Secondly, a DCIAV (double check, intermediate atmospheric vent) style vacuum breaker would prevent the water on the house side of the system from migrating back to the irrigation system. An RPZ could also be used. Both the RPZ and the DCIAV provide an atmospheric break in the piping, meaning there is virtually no possibility for back siphonage.

    Your problem sounds to be as one of inadequate supply for everything you are trying to do. I would surely hope you don't have a pump for the irrigation system, as that would explain a lot. Perhaps reducing the size of your zones (adding more, making each zone 'smaller') is your best bet. You most likely are exceding the flow rate of your well vs demand on your larger zones. Please don't ignore this part, as it is most likely the crux of your issue.

    With all the examples above, and what you've already done, your system is 'closed' and requires a thermal expansion tank for your water heater. Make sure you have one.
    Last edited: Mar 15, 2006
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,280
    Location:
    Bothell, Washington
    [​IMG]

    I like to use a double check valve for irrigation backflow.

    Series: 007
    Description: Double Check Valve Assemblies
    Size Range: 1/2 to 3 in. (15 to 80mm)

    Series 007 Double Check Valve Assemblies prevent the backflow of contaminated water into the potable water supply. It consists of a bronze (1/2 to 2 in) or fused epoxy coated cast iron (2 1/2 to 3 in) body construction that is easy to maintain and service. Series 007 is ideal at referenced cross-connections identified as non-health hazard applications. Check with local inspection authorities for installation requirements. Maximum Working Pressure: 175psi (12.06 bar).


    http://www.wattsreg.com/
  4. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,383
    Location:
    Yakima WA
    You're thinking right about the backflow preventer. These are required on public water supply systems. Basically what you do is tee the main supply line to feed untreated water through a backflow preventer for the irrigation and the other side of the tee into the treatment device. This will do two thing for you. You will not be irrigating with the treated water, and you will not be syphoning water from the irrigation side into you household supply. I don't remember the brand of backflow I use, but any decent plumbing supply should be able to provide a suitable one. In my city, I am required to have an annual inspection to verify the backflow is still performing properly. You won't have the legal requirement that I do, but I'd suggest you find a plumber that can test yours for you own safety. I pay $25 for my inspections.
  5. dubldare

    dubldare Plumber/Gasfitter

    Messages:
    286
    Location:
    MN/ND
    If I'm reading him right, he is siphoning water from the treatment system (house water) into the irrigation system. Any backflow device solely on the irrigation branch will not stop that.
  6. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    A Watts #7 check valve installed between the hose bib / sprinkler and treatment system with the flow direction towards the treatment system will solve the problem. The sprinkler should have a backflow on it also.
  7. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,383
    Location:
    Yakima WA
    I stand corrected, Dubldare is correct. I misread the question. I wonder if a double check valve in the potable line might be the answer. In other words, a double check valve in both lines. This is a guess, I'd sure check deeper into this before investing in the valve, but it seem logical that it would work.
  8. sp00kster

    sp00kster New Member

    Messages:
    15
    Thanks for all the responses - Guess I am still am a bit confused by posts. I will recap a bit to explain.

    1st - water supply enters through basement wall into pressure tank
    2nd - T's off immediatly (sprinkler - potable house water treatment system)
    3rd - sprinkler system already has an anti-siphon valve outside to prevent potable water contamination
    4th - Potable house water treatment side already has a Watts (Series: 7) dual check valve installed immediatly after T - to prevent potable treated water from siphoning into the sprinkler system.
    5th - Between our well service, sprinkler service and water treatment service (all of which are pointing fingers at each other)

    Guess what is confusing me is what is the difference in a back-flow prevention valve and dual-check / double check valve. If / when you go to Watts url (www.wattsreg.com) all are labled "back flow prevention valves". For the life of me I do not understand how when the sprinkler system is on it is able to siphon the potable house water back through this dual check valve (replaced twice), in the first place. Must be some serious negative pressure or something. I have no problem purchasing what ever it will take to stop this backflow just that I know from experience that it will take more than a Watts (Series: 7) dual check valve / back flow preventer.
  9. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    How do you know it is backflowing/siphoning?
  10. sp00kster

    sp00kster New Member

    Messages:
    15
    All of this was brought to my attention in the first place when we noticed that chlorinator was using an extremely large amount of chemical during the watering season. So we called our water treatment service company out and they are the ones that realized that the chlorinator was running while the sprinklers were running (due that chlorinator was wired into the well pressure switch (creating a very concentrated solution in the retention tank)). At the time there was not even the thought of it siphoning out to the sprinklers just that the chlorinator was running regardless whether it be potable water or sprinkler. So they sent plumber out who installed a single check valve, pressure gauge and a independant pressure switch on the potable water side. So I am told that now the chlorinator will only come on when potable water side pressure drops thus tripping the indepandant pressure switch and allowing the chlorinator to run with pump. He showed us by engaging the sprinkler system and the house pressure did not drop and the chlorinator did not come on. Later we found that it did work on zones 1 - 3 that were very low volume (pop-ups and drip) - until the high volume zones 4 - 7. As soon as any of these zones would engage the potable water pressure side would quickly drop and the chlorinator again would engage. I also used our water test kit to test for chlorine via the sprinkler system on zone 4 (5ppm).

    I called our water treatment service company back out and they in turn sent plumber back out - he in turn replaced check valve with dual check valve. I was not home to test while he was here (still did not work). Now they are all saying that is best they can do. Now makes me wonder if he really was a plumber in the first place.

    Any way you have now heard the long version and any help would be greatly appreciated
  11. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    I am wondering if

    #1 the chlorine is affecting the check valve some how.

    #2 if there is a cross connection somewhere that you don't know about.
  12. sp00kster

    sp00kster New Member

    Messages:
    15
    Chlorine can only get to the valve in the first place because of siphoning. I have attempted to create a diagram in Microsoft Word as an illustration - I will attempt to attach.

    Attached Files:

  13. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,383
    Location:
    Yakima WA
    The only thing I can think of is that the check valve is not functioning. The backflow I use is exactly the one Terry pictured earlier, and should do the job. I would have it tested to make certain it is functioning properly. They can fail, that's why my city requires an annual test.
  14. sp00kster

    sp00kster New Member

    Messages:
    15
    Ok - Will replace again - a big thanks to all of you for your input. Ever need any advice on replacement windows or doors feel free to give me a shout and perhaps I can return the favor!!!

    Best Regards
  15. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,383
    Location:
    Yakima WA
    NOTE: I was only suggesting you have it checked. While this seems to me to be the only logical possibility of the cause of your problem, I'm sure as heck no expert! Any irrigation supply company should be able to test the backflow valve. If it's working OK, then I'm stumped.
  16. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,020
    Location:
    Cave Creek, Arizona
    siphonage

    Either you are misstating the problem, or you have a different problem than you describe.

    1. Any "backflow" device will prevent the irrigation water from flowing into the house. It will not prevent anything ahead of it from flowing into the sprinkler system.

    2. The irrigation system should have a positive pressure almost equal to the house pressure, especially at the connection point, so siphonage cannot occur.

    3. If the system is piped so that aspiration can occur and draw the treated water from the chlorinator, then that is a different problem and needs a different cure than a backflow preventer.
  17. sp00kster

    sp00kster New Member

    Messages:
    15
    HJ - I am not sure exactly on the aspiration part in #3 but as for the rest of #3 all is correct and is confirmed with a water test of the well water at the sprinkler head as well as simply watching the potable water side pressure gauge drop to match the well pressure. Using chlorine free test strips. That the sprinkler system is siphoning / sucking / drawing whatever the best term would, chlorine treated water through the dual check valve. There is a Word attachment with a detailed diagram a few posts back - perhaps may shed a clearer picture. As for the other examples they are not relative to my problem. The sprinkler line T's off 3' prior to the potable water dual check valve and chlorinator is another 3' downstream.
  18. sp00kster

    sp00kster New Member

    Messages:
    15
    just adding one more note as an example - Potable house water pressure at 50lbs and holding and does not deviate on 1-3 low volume sprinkler stations(well pressure during is at 45lbs constant. Then comes zone 4 (well pressure during is 35lbs constant), potable house holds at 50lbs for about 30 seconds then slowly starts dropping soon matches well pressure at 35lbs - also trips independant pressure switch when it hits 35 pounds thus starts chlorinator.

    I can actually stop the siphoning by going all the way accross the room on the other side of the water softner where it goes into the house and close the house supply shutoff ball valve - the potable house pressure stops dropping immediatly and sprinkler continues on. As soon as I open house valve back up pressure continues to drop to well pressure.

    The plumber that installed the dual check confirmed what I have posted but said he had never seen anything like it and would have to get back with us. Later he - water treatment company left message on answering machine stating they have done all they could do.
  19. dubldare

    dubldare Plumber/Gasfitter

    Messages:
    286
    Location:
    MN/ND
    A RPZ on the house side of the irrigation piping will prevent treated water from backfeeding to the irrigation system.

    It will leak from the relief/drain when 4-7 are on. This is the price you pay. All RPZ's will leak if supply pressure drops too low.

    Either size zones 4-7 the same as 1-3 or deal with high pressure going to low.


    Additionally, you should have a relay to prevent chlorinator operation when the irrigation system is running. Time the irrigation system to run at night when you're not using water in the house.
  20. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,020
    Location:
    Cave Creek, Arizona
    backflow

    You cannot have siphoning with your system. You either have backflow because the pressure downstream from the chorinator is higher than the dynamic pressure at the irrigation system's tee, which is implied that it starts when the house pressure starts dropping, or your flow is so great that it creates aspiration. Siphonage could only occur if there were a way for air to enter the system past the chlorinator as the treated water is drained away, and even a back pressure could only occur until the two pressures were equal, and since water is not compressible, that would occur very quickly. As stated previously, your description implies a different problem.
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