First post here. I've read through most of the vertical loop posts, but didn't see my question addressed. I'm doing a DIY geothermal installation in Arkansas and plan on installing 3 vertical loops, each 230' deep and 20' from my basement wall penetration. I'll be making the header in my basement mechanical room. I'm planning on 1" dia by 510' long Centennial Plastics pre-made U-bend loops. My water well ~100' from the geothermal wells is 100' deep with water to within ~10' of the surface. Assuming these geothermal wells will have approximately the same amount of water in them, how much additional weight will I need to add to the water filled and pressurized loop pipes to sink them to the bottom of these wells. Will one 20' stick of 1/2" rebar attached to the U-bend bullet and pipe be sufficient to sink the pipe? Assuming 20' of 1/2" is enough, would it be better to cut the rebar in half and attach two 10' pieces to the U-bend - one on each side? Seems like it might be easier to get it started into the hole with two 10' pieces rather than one long 20' piece. Also, how is the steel typically attached to the U-bend? Packing tape? Duct tape? Gorilla tape? The pipe I looked at at the local supply house had 1/2" grooves on either side of the U-bend bullet to accommodate two pieces of rebar. Thanks.
HDPE is lighter than water (edit: less dense), but not by much. I've seen rebar attached, but the drillers' on here will give you much more experience opinions than mine.
why do the pipes sink when you fill them with water in pond loop applications? They can become buoyant with ice forming around them, that is why they need weights on them, but they sure sink when filled. Different density of water at different temperatures? I guess I got to look this up.
I stay corrected, water density is higher than HDPE, only when water is above 160F its density gets less than HDPE, which also expands more than water with higher temperature. Our slinkies definitely always sink. We use a couple pounds of metal ties per slinky...????
Yeh, they are sorta neutrally buoyant. I only know this from re-floating one and having a couple of straps break off.
As always, location-location-location. It takes what it takes to get the loop down the bore. How much it takes depends heavily on the stability of the bore and the amount of suspended solids in the bore. No 2 locations are the same, ever. Is the driller placing the loop? Who is paying for the weight? Mud rotary or air percussion, or sonic, for the drilling? I use a 150# hole loader on a cable that is used for inserting the loop, and once at the bottom it is retrieved on a cable via a high speed winch. YMMV Eric
Thanks for the replies. I've since changed my design to 3/4" x 510' (255' + 255') vertical loops. I bought the pipe last week. That should make it a little easier to get the pipe in the hole. Also, after talking to my geothermal well driller, he said he would put the pipe down the hole. All I have to do is provide the pipe. I asked him about how much rebar was needed so that I would be sure to have the correct amount on hand and he said none. He said he had a way to get the pipe down the hole, but didn't provide any specifics. He said he has 4 trucks and the truck that he uses in this area is a rotary rig, Gardner Denver 1000, and 34' long if I wasn't mistaken. He said that if all he hits is red clay then shale/sandstone typical for this area, that essentially all that would be left in the hole is water when he is finished.
I'm a little late to the party... I use a 20' x 1.25" solid steel rod for loop insertion and also. It's attached to our sand line winch of the drill rig.
Just curious, but how do you attach that steel rod to the loop to push it to the bottom of the hole and then how do you unattach it from the loop pipe to pull it back out of the hole?
The steel rod has a 3ft long 1/2" pipe welded to the end of it. That 1/2" section gets inserted into a piece of 1/2 pvc pipe which is taped to the end of the loop. The loop goes down and when we pull the pipe upwards it just slides right back out of the 1/2"pvc. Easy Peasy. We also just duct tape the pipe right to the loop when we forgot to bring pvc with us on the drilling rig (happens often). When you give the pipe a quick jerk upwards it snaps the tape right off.
We do it a little differently. When you cut the end of the loop off to fill with water, we duct tape that to the loop and insert the rod end into that. No more forgetting the PVC. If we think the bore may be problematic, we duct tape the loop to the bar as a extra measure and then " quick jerk " the rod back as Dan explained. We welded a 3/4 inch x 6" bolt to the end of our bar. Eric
Just an update to this thread. I got my geothermal wells drilled the past couple of days. I ended up using some leftover 20' sticks of 1/2" rebar from my new house build, cutting them in half, and taping each 10' piece on either side of the U-bend (it had a U groove on each side just for this purpose). Pipe slide down the holes no problem. I filled the pipes with water before hand. Well driller wanted to cut the ends off the pipes, but I didn't want that. The Centennial Plastics Earthloops come with tire valve stems in the end and I just removed the valve cores and filled the pipes using my garden hose and an adapter used for filling tractor tires with water. I had to let it run for ~10 minutes to get all of the air out of the lines. The well driller ended up going down 240' or slightly more rather than 230'. I have between 235' and 240' of loop down the holes. Now my pipe tails won't reach the basement wall, so I will have to fuse some more pipe on the ends in the trench to get to my header in the basement. Not a big deal. All three wells (20' spacing) filled with water to ~20' from the surface. Drilled through 30'-35' of hard red clay, then black shale for remainder. Hit water at around 40'-45'. Not big flow, but more than enough to fill the wells. It took ~3 hours per hole including setup of the truck.
