drip system question

Discussion in 'Irrigation' started by Mats, May 28, 2003.

  1. Mats

    Mats LawnSite Bronze Member
    Posts: 1,931

    I'm installing a drip system for a tiny back yard which includes a two story deck. The water supply is on the ground level and that is where I want to install the controls - valves and timer. One valve will control the ground zone and another will control the deck's container plants. The zone for the ground will get watered longer and less often than the containers. The water supply is at ground level of course. And that is where I want to put the valves and timer. But I'm going to have 80' of 1/2" poly servicing the upper deck - and it will be 12' above the valve/backflow preventer.
    Every time the water shuts off I'm going to get a lot of water coming out the backflow preventer. Short of putting that valve up on the second level, how can I design this so the backflow preventer is above the upper line?
     
  2. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    Use an RP (reduced pressure vac.) instead of a PVB. Water won't dump out and it will probably meet building codes this way.

    If you're unsure of what an RP is or why it is necessary in your application, you may want to get someone else to do it who knows more about it.
     
  3. Mats

    Mats LawnSite Bronze Member
    Posts: 1,931

    >Use an RP (reduced pressure vac.) instead of a PVB. Water won't dump out and it will probably meet building codes this way.

    Thanks Dana. You're right, I didn't know about RPs, but have since read up on them on Stryker's site. I priced one at Ewing and it's over $100. As that seems a bit pricey for such a small drip system, I asked him if he had any other suggestions. He said an atmospheric vacuum breaker on the top deck would work just fine. Does that sound right to you?
     
  4. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    AVBs are not really industry standard anymore. AVB or PVB will have to be 12" above any sprinkler outlet in the lawn - at least according to our local codes, yours may be different. An RP is used when there is elevation change in the lawn where the heads are going to be above the backflow preventer.

    An AVB must be installed AFTER each individual valve. So if you have 6 valves (or zones) you need one for every valve. A PVB or RP is installed BEFORE your valves or manifold.

    An AVB will still dump out water though. It will not solve your problem. A PVB won't dump water as it will be under constant pressure, but it may not work out in your situation. It sounds like an AVB or PVB in your situation will need to be very high in the air.

    My advice, do it right the first time, spend the extra money and instal an RP.
     
  5. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Posts: 1,712

    Cost. That brings up something for me to Tee off on. I seldom care what a "solution" costs. I try to provide appropriate solutions for my clients at the lowest cost. But if the solution seems absurdly expensive it is not my problem and I don't feel bad. Let them decide if the upper deck needs auto watering based on the price to do it correctly.
     
  6. amen....if they balk at the cost to do it right, walk away.

    PS: If the flow through the valve is less than 1 gpm.....be careful, pot valves are tough. The valve may not be reliable at the low of a volume.
     
  7. Mats

    Mats LawnSite Bronze Member
    Posts: 1,931

    > Let them decide if the upper deck needs auto watering based on the price to do it correctly.

    OK, you guys have convinced me to go with the proper backflow preventer. $100 to do it right is not that big a deal.

    And with this unit, I'll be able to put all the controls under the lower deck in a less conspicuous location. That's a big plus.

    Now I've got a question. Stryker says, "R.P. Units spit out water on occasion..." How often does this occur and what does he mean by 'spit'? The Anti Syphon valve will dump big time when ever the valve closes. Remember, I'll have 140' of 1/2" poly tubing above the controls.
     
  8. Personally I would pass on this job. Too many chances for bad things to happen.

    Stuck valve, flooded deck, flooded house?
    Split tubing in the sun on the deck, same scenario.
    Broken emitter squirting on roof or into window?

    Not worth it for me....but we don't get many people wanting this so it is easy to pass on. Perhaps in your area more people want this...if so you could figure out a reliable way to do it and create yourself a nice little niche.

    Be cautious though
     
  9. daveainthere

    daveainthere LawnSite Member
    Posts: 12

    sprinkler guy is right ... PS: If the flow through the valve is less than 1 gpm.....be careful, pot valves are tough. The valve may not be reliable at the low of a volume


    AND what would be wrong with a simple check valve after any anti siphon device? just a thought
     
  10. Mats

    Mats LawnSite Bronze Member
    Posts: 1,931

    >AND what would be wrong with a simple check valve after any anti siphon device?

    Yes, that's exactly what I'm leaning towards now. I asked Hydroscape and they thought a swing check valve after a normal anti-siphon BP would be more than sufficient for such a small zone.
     

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