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Thread: Drainback system?

  1. #1

    Question Drainback system?

    I am building a new house, with a "lake well" for water. A submersible pump (Goulds, 10 gpm) on the lake bottom (about 15' under water, with a filter) supplies water to the house, which sits on the top of a 15-20' cliff. My contractor has indicated (as have the neighbors) that, because the pipe (actually, 1" poly hose at the important location) transitions from a vertical to a horizontal orientation at the top of a 15' cliff before going underground, I will need a drain back arrangement to keep the water in the hose from freezing in the winter. Is there such a thing as a "drain back" valve? I think one posting in this forum mentioned such a thing. Also, it seems that if the hose is drained to the water line every time the pump turns off, I will also need some sort of air venting system (unless its in the drain back valve) or there will be a lot of air getting pumped into the water supply system. I was told by one of the neighbors that he implemented this system by simply installing a check valve in reverse, to allow air into the system when the pump stopped, with a regular check valve upstream to keep the water in the house. Does this make sense? Thanks.

  2. #2
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    I use 3/4" check valves for the air inlet. The drain back valves only let go when the pressure is relieved from the line. I am not sure what this pressure is, but a 60 foot cliff will keep 26 lbs. on the valve and may now be low enough to let it open.

    bob...

  3. #3

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    If you take a look at any design for a submersible pump with standard [no bladder- glasslined] storage tank, you will see exactly what you seek. Rubber type [small constant leak] draindown valve in a tee at water line, checkvalve with snifter valve near the tank. Tank with a air release valve- float type. All reliable components and on every well drillers / pump guys truck. You are the poster child for using NON bladder tanks in this situation. Every Myers pump I buy has such a diagram in the box. If you use this set up the air becomes your friend and you dont need to deal with it at all. In my experience the rubber drain down valves leak up to about 50 psi - if it wont, take a hot screwdriver and make a bigger nub on the flapper. The tiny air valve - snifter valve i.e. schrader valve from your tires sans spring is enough air entrance - unless you are in the arctic. Only problem is bugs and debri - wrap the little item in cheesecloth or pantyhose. Remember that submersible pumps should be placed in a pipe to induce water flow across the motor or they may overheat - simulated well casing.

    What do you do with this water - treat it before use?

  4. #4

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    Quote Originally Posted by speedbump
    I use 3/4" check valves for the air inlet. The drain back valves only let go when the pressure is relieved from the line. I am not sure what this pressure is, but a 60 foot cliff will keep 26 lbs. on the valve and may now be low enough to let it open.

    bob...
    Thanks -- I think I understand, but I was thinking of putting the check valve at the top of the line, in the house, to let air in; in this case, there should be no pressure, correct? Or will that not work?

  5. #5

    Default One point of confusion

    Quote Originally Posted by Raucina
    If you take a look at any design for a submersible pump with standard [no bladder- glasslined] storage tank, you will see exactly what you seek. Rubber type [small constant leak] draindown valve in a tee at water line, checkvalve with snifter valve near the tank.

    What do you do with this water - treat it before use?
    I think I've got it, but do I need to install a draindown valve at the waterline? I had the installer defeat the stainless steel checkvalve on the pump when it was installed (as per the pump instructions). It seems like the water should just drain back through the pump when it stops, because the checkvalve was drilled. The idea of the checkvalve with snifter is to allow the air in to do this correct (?)

    We have a 20 micron pool filter between the intake and the pump, a 5 micron filter in the house (before the tank), and an ultraviolet light to treat the water. I think there should never be a risk of overheating (?) because the pump is in 18 feet of water on the bottom of the lake (in a housing).

    Sorry if this is repeating too much; I'm not a plumber and no one around here appears to be an expert at this type of system.

    How to install an ultraviolet light

    Last edited by Terry; 06-14-2010 at 01:08 PM.

  6. #6
    In the Trades Bob NH's Avatar
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    A submersible pump (Goulds, 10 gpm) on the lake bottom (about 15' under water, with a filter) supplies water to the house, which sits on the top of a 15-20' cliff. My contractor has indicated (as have the neighbors) that, because the pipe (actually, 1" poly hose at the important location) transitions from a vertical to a horizontal orientation at the top of a 15' cliff before going underground,

    We have a 20 micron pool filter between the intake and the pump, a 5 micron filter in the house (before the tank), and an ultraviolet light to treat the water.

    You are saying a couple of scary things. A pump "on the lake bottom" is a disaster. The pump should be several feet off the bottom, and several feet below the surface. In 15 ft of water, I would put the inlet between 4 and 6 ft off the bottom.

    A 20 micron filter on the inlet is not going to work. It will plug and cause cavitation of the pump. And how are you going to change it in the winter? You WILL need to change it, often.

    I have installed lots of pumps in lakes, but NEVER with a filter on the suction side.

    If there is a hump in your pipe before it goes underground, it will not drain back completely. If you don't admit air, it will not drain, and if you do admit air it will create a bubble at the top and lose the siphon while there is still water in the pipe between the hump and the check valve at the water tank.

    You should bury the pipe or insulate and heat it.

    If you are using lake water, you should chlorinate as well as filter it. Without persistent disinfection you will get nasty thingies growing in that 5 micron filter.

    You will also need to assure that there is a relief valve between the pump and the 5 micron filter. Speedbump is going to have apoplexy when he reads that you have a filter between a submersible pump and the tank. He won't have anything good to say about that 20 micron on the inlet either.

  7. #7

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    So the drilled check valve on the pump works too and maybe it solves [some of] bobnh's concern with the inlet filter - you are backwashing it every time the pump shuts off - dont drill it, take it out so you get a strong backflow. Just get a standard well checkvalve drilled for a schrader valve and a pressure switch and put it at the tank. [ if anyone thinks the backwash effect is valid then you might use a few schraders or the standard checkvalve to admit air more quickly] I assume you are using the standard tank with air release valve to deal with what will be a lot of air. Dont put any "traps" in the line. You could also run the pipe in a 4 or 5" sleeve and insulate it in the area from water to cliff top -if you are not in northern wisconsin.

    I think I would drill a well at the house and tap the lake water in a much cleaner manner. When you account for maintenance and disinfecting you could spend a lot on the well and come out ahead. Who want to fiddle with his pump from a boat or with wet suit?

  8. #8
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    It's a submersible pump Bob. But I agree, no strainer on the inlet side of any pump. Filters no matter how cheap or ineffective, should be on the pressure side of the pump and after the pressure switch/tank.

    Raucina is correct on the check valve, remove it. Then you won't have to worry about that little drilled hole plugging up and letting things freeze.

    Instead of schraders, use a 3/4" or larger check valve or better yet a foot valve at the house. When the check valve beyond the foot valve closes, the foot valve will open and let the air in. And it won't plug up. Don't use plastic, use brass or stainless.

    bob...

  9. #9
    DIY Senior Member Phil H2's Avatar
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    More ideas from the peanut gallery.
    Maybe terminology differs around the country and from one industry to another. But gerhard may want to talk to his contractor about using an air vent valve. They are primarily designed to let the air out of the piping, but they also let the air back in when the piping has no pressure.

    I live in a warm climate so freezing is never a problem. But, if the piping between the house and the cliff has a low spot that is higher than the cliff. Something must be used to drain this. I think someone eluded to a valve used in the sprinkler industry.

    The biggest challange I see with this system is refilling the pipe every time the system cycles. Once the basics are covered, I would try to think of creative ways to reduce the number of times the pipe must drain completely. Adding a big pressure tank is one method. Temperature sensors and solenoid valves are an option. But, they would make a complicated system which can be hard for others to maintain or repair.

    Around here, a foot valve is just a check valve used on the suction end of piping. It doesn't have pipe threads on the inlet (or socket for PVC). They typically have some kind of grate. So, I am curious about the valve speedbump is recommending.

    Here is a couple thoughts on the strainer on the pump inlet. First, I hope there is an easy way to access it when it becomes restricted. Most suction strainers have plenty of open area so they do not reduce the suction pressure. They keep the big things out that will tear up the pump.

  10. #10
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    The foot valve is used in place of the schrader valve. It just won't plug up like the Schrader will.

    This is the order of the system we are proposing.

    Pump > Bleeder > Pipe to house > Tee with foot valve installed > Check valve > Tank/Pressure switch.

    I'm not fond of this system either, but it is the simplest way to get the job done. The reason we went with the foot valve was to keep from changing Schrader valves all the time.

    Some people think we would use the Schrader valve so we get a call back. Nothing could be further from the truth. We lose money on these calls. Two guys, a $65,000 truck that gets 6 miles per gallon for a $69.00 service call and a $3.00 Schrader valve won't pay the light bill.

    bob...

  11. #11

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    Sure the check valve works without problems because it has a big hole in it - big enough to suck a mouse into your pipe that was napping there. Schrader valves are reliable if they are wrapped in some filter material. If you go with either, filter the inlet air somehow. Everyone forgets - no one mentions - that the make up air in any system is a source of contamination. Here we have mud bees that plug every hole 1/4 to 3/8+ in diameter each year - they hold up to 150psi, and almost cost me a 10,000 dozer engine when the fire extinguisher hesitated....

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    The foot valve has a perforated screen on it. And the Schrader valves plug up from the inside from the mineral in the water. Not mud dobbers.

  13. #13
    Rancher
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    Quote Originally Posted by Raucina
    almost cost me a 10,000 dozer engine when the fire extinguisher hesitated....
    Why do you have fire extinguisher's on a Dozer?

    Rancher

  14. #14

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    Joking, right? In case not, most larger dozers and excavators have fire extinguisher systems piped in for push button operation. Oil, twigs, powdered dry grass, 4500 psi oil leaks, do interesting things on the exhaust manifold, usually deep in a dry forest.

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    I'm still trying to picture this suction strainer on a submersible pump. I have built submersibles inside the lake strainer I sell, but I don't know how you would hook a suction strainer to the inlet of a sub.

    bob...

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