I've come across a few threads where a pro recommends soaking a closed loop field when the system is not performing well. I am trying to understand what soaking accomplishes? Does any have a link to a technical info that would explain the process and its effects?

I suppose that the purpose is to mimic ground water flows and to equalize the temperature around the loops. The reason I am looking for some technical info is that I have a property with a well producing more than adequate flow to support an open loop system. However the state demands any open loop system returns the water through either a return well or by using an infiltrator system (basically a septic system without the tank). Even with this requirement they want the total well flow for geothermal use to be less than 18 gals/min which would be very close to the minimum requirement for my house.

Is there any benefit to a hybrid loop system that consists of a closed loop at -10' elevation, backfilled approximately 6' with select fill and topped with the infiltrators and top soil to augment the open loop? The infiltrators will handle all open loop discharge and all storm water from the roofs and driveway. So there could be a fair amount of water moving through the loops.

I'm not intimately familiar with the concept but here is some free-and-likely-worth-every-penny armchair engineering:

Adding water could help a field in 3 ways

1) Adding high specific heat mass in contact with loop tubes - water has much higher specific heat than ground solids so having it in contact with tubes improves loop's ability to absorb / yield heat.

2) Water is a much better conductor than ground solids, particularly dry ground solids. Having it in contact with loop tubes will speed heat transfer to / from tubes

3) Clayey soils are expansive, meaning they expand (and contract) depending on whether wet or dry. Tubes placed in wet clayey soils that later dry may lose contact with soil as soil contracts. Any air space between ground solids and tubes would serve as a really good insulator, a thoroughly undesirable condition in a loop field. Added water could re-expand contracted clay soils renewing contact with tubes.

Adding water to a loop field could be bad in a cold climate if it is frozen by the loop field. Ice is a poor conductor of heat and the associated expansion could wreak havoc on structures / foundations too close to field.

18 GPM through an open loop system should support 12+ tons, depending on the source water temperature. That's a lotta tonnage...what are your (hopefully calculated) heating and cooling loads?

Off the top of my head dumping open loop water onto a horizontal closed loop system sounds like a potentially nifty idea as long as risks or freezing and erosion are assessed and planned for.

All I would add to the above is that for a loop that has recently been installed, soaking is always a good idea to settle the ground around the pipes.

As I stated in another thread, by saturating dry ground around a loop, you can either double or triple the amount of heat ( depending if you have clay or sand) you can exchange with the ground.

engineer,

I had a thought about soaking a geo loop but in an odd way. The concept was to put a DX copper loop in a 1000 gal tank of water. By using thermostats, flush the tank with fresh water as the temp gets too cold/hot.

We are building on a public lake. But I'm sure we can't sink a loop in the lake. But maybe we could drill a well close to the water table and pump this flush water. I would think the water would be very dirty and not work in a pump and dump system.  We are probally 150' from the waters edge and about 30' above the water level. The well can't be drilled at the edge because the land is protected.

The down side is it would be like a pump and dump and a DX system combonation. The up side would be no loop field and the DX lines would be accessable for any repairs via the tank.

I think this concept could work for folks who had a spring above there home.

Patrick T.

I don't see why that couldn't be made to work. I'm a bit leary of the long copper tubes in the ground aspect of DX, but I can see the attraction of not having to deal with the circulating water system, scale, and what not.

Where are you? I'd be concerned with freeze protection.

Thinking 'out loud' if you got a cylindrical plastic Ag tank with an opening large enough to climb into and put the required footage of DX tubing in a vertical slinky coil around the perimeter of the tank, you could easily drain it for inspection / cleaning

The required footage to be immersed could be calculated via basic thermodynamics, and would likely be much less than if buried underground.

You'd have to work out cost of running shallow well pump and how to handle the discharge water. Another issue could be thermal stratification in the big tank. Agitation via a small fountain type pump at the bottom might be needed. Stratification could be overcome by properly configuring the DX tubing so convection counters strtification - you'd have to work out the summer and winter aspects of this.

Soil composition will dictate how well the lake water connects to the ground water. If the lake level changes drastically, design for lowest level.

I'm confident this all could be worked out, but there might be bumps along the way.

Curt Kinder

Curt,

I'm in Southern IN. The proposed tank/s would be underground as well as the well feed line. Discharge would return to the lake via a ravien that flows a bit during rains.

I'd like to think that if I could sink a well within 100' of the lake that there would be water nearly at lake level but....

 

Patrick T.