Variable pumps & drain back systems [RE-wrenches]

[Windy Dankoff, Dankoff Solar]

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The Grundfos SQ and SQE pumps

>>Windy,Living in places where the cold weather and ledge can make 
>>burying water lines below frost level tough ,there are what is 
>>called a drain back system. I'm sure that you have seen a few , my 
>>question is DO these types of ramp up pumps work w/ the drain back 
>>system? And if so where can I get more info on them?

Tump,

ANY submersible well pump can be set up to drain back. I don't think 
there is any reason why the SQ type pump would have a problem. It is 
the normal mode that any pump would see the first time it's turned 
on. All AC pumps are all centrifugal type. You only need to remove 
the normal check valve from the pump outlet, and water will freely, 
quickly drain back down through it. In the case of a positive 
displacement DC submersible like SunRise, there are check valves in 
the pump that make it work. In that case a slow, intentional leak in 
the pipe allows it to drain down, however slowly. That can work fine, 
too. The intentional leak is called a "weep hole". It can be a 
pin-hole, but some installers use an irrigation dripper if the 
pressure isn't too high for it. The dripper is less susceptible to 
clogging than a simple hole or tiny valve.

If the pump is to fill a storage tank, spilling in from the top (open 
discharge), then you have the simplest and inherently reliable setup, 
assuming the pipe drains freely.

If the pump is to fill a pressure tank, you need to install a vacuum 
breaker at the tank, to let air in so the water can drain back. The 
breaker spits a little water each time the pump starts up and refills 
the line. And, you can have problems if the breaker or the check 
valve at the tank are imperfect. I have one customer however who has 
had that system in place for 7 years and it's been fine. He has to 
accept the ever-present moisture from the spitting vacuum breaker, 
that's all.

Windy

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