The Loops

The Loops…

The Loops… This is probably the simplest portion of the system to understand.  Unfortunately, it can also get fairly complicated to plan and install.  The Loops are the portion of the system that bring water/fluid from the ground and give it to your new heating and cooling unit GSHP to heat or cool your home. 

This is what 2400’ of ¾” HDPE pipe looks like.  It’s 4 Loops. 

The Loops are basically very long pieces of garden hose (HDPE pipe) that have water in them.  These Loops carry fluid to and from the GSHP.  Because the water in the hose is underground, the temperature of the water is a nice constant temperature that your GSHP uses for free.  That was the easy part, now let’s dig into the Loops just a bit more. There are generally two types of fluid transfer systems for a geothermal system… Open and Closed.  Either one of these types of systems still require water to make them work.

This is how I set up my Loops.  This is the evil Red Loop that leaked.  The red nylon rope going up the side of the Loop was one of a few color coding I schemes I used to identify the Loops.  

March 2017: I would not wind my loops like this again.  For me it works fine; but, I think there is too much propensity for a kink.  Also, there is a concern with too much loop in one place creating thermal transfer issues.  Neither of these are an issue in my setup; however, looking back, this was not a great design.




An Open system uses some water source, (stream, well, pond, etc.) to pump fluid out of it directly, send it in to the GSHP and then dump it out somewhere else.  (Pump and Dump).

Open systems are pretty easy to deal with UNLESS your water source has a tendency to dry up or run at a very low rate.  Running at a low rate creates problems for the GSHP since they require a certain amount of water going through the system per minute in order to operate efficiently.  For the sake of argument, let’s say that most folks will need about 9 gallons per minute (GPM) in order have an operational system.  If you can not provide a sufficient water flow through out the year, do not consider an Open system. 

Calculating the size and the amount of pipe that you will need is fairly easy.  You will only need one pipe coming in and one pipe going out.  Calculating the cost of the pipe based on length is pretty simple.  Typically, you will use 1.25” HDPE pipe.  Another issue is figuring out how much it’ll cost to bury the pipe to and from where you need to pump and dump.

Open systems get their fluid “at temperature” right at the source of where it is picked up.  So, if a stream has 45 degree water running it in year round, the GSHP will get 45 degree water to work with.

Finally, Open systems are generally much easier and cheaper to setup.  If you can go this route, please do so.

A Closed system circulates the same fluid around and around and around.  It works like the cooling system on a car.  The engine warms the coolant up and the radiator cools it down.  The same fluid is used over and over again.

Closed systems typically rely on “Loops”.  A Loop is a long piece of pipe that has fluid circulated in it.  As the fluid travels down the pipe, the fluid begins picking up the same temperature of its surroundings.  The GSHP uses the temperature of that fluid, gets what it needs and puts the fluid back in the Loop.  The water circulates in the Loop long enough to bring it back to ground temperature before it goes back to the GSHP.

The Closed Loop system has to be designed in such a way as to making sure that the “used” fluid (the fluid that the GSHP just used) has enough time to “heat up” or “cool down” before it goes back into the GSHP.  In this case, the Loops HAVE to be long enough for the proper heat transfer to take place.  For a “typical” dirt install, the Loops have to be about 600’ in length for proper heat transfer to take place.

Example:  Let’s say it is summer and the GSHP is taking the “cold” out of the water, putting it into your house (for cooling) and then putting the leftover “hot” back into the Loop.  Let’s say the Loop is ten (10) feet long.  There is no way that the “hot” in the Loop will cool down fast enough before it gets to the GSHP for re-use.  It would be like using a car radiator that was the size of a box of band-aids.  (The car engine would never cool down because the radiator is not big enough to cool the hot fluid.)  In this case, the system will run very very poorly or not at all.  Again, the Loops have to be long enough for the fluid to take on the thermal properties of its surroundings BEFORE getting back to the GSHP or else this system will not work well.

Closed Loop systems can be setup up in many ways.  For instance, you can put a Closed Loop system in the dirt, pond, stream, or well. 

If you have a lot of land with no water nearby, then you are putting this in the dirt.  If the dirt is dry and sandy, then the Loops will pretty long…  let’s say 900 feet.  This is because the heat transfer between the ground and the Loops will be poor.  If the soil is clay like and fairly moist, then the heat transfer will be good and a 600 foot Loop will be just fine. 

If you do go into the dirt, you are looking at putting this 12 inches below the frost line.  The lower you go, the less your Loops will be affected by the radiant energy of the sun.  (This is a good thing.)  The lower you go, the costlier it’ll be to bury the Loops.  This is a trade-off.

If you do not want to dig up your land, you can drill bore holes.  One bore hole for each ton of heating/cooling and you need to go down about 250 feet for each hole.  (This gets very expensive and really should only be used if you have a small lot or you own a drilling company.) 

In a drill scenario, some folks like to use copper (instead of HDPE pipe) in order to get great heat transfer.  This reduces depth of the bore and reduce your costs; however, copper is not exactly cheap either.  I believe these are called “DX” systems.  I am not familiar with these Loops at all.

If you own a small lot, the expense of drilling can become a huge issue.  Geothermal in cities will probably not do well.

Putting the Loops in water creates an excellent heat transfer and allows you to shorten your Loops.  If a pond, you should probably make sure that it is at least 8’ deep.  If a stream, the stream needs to run nicely all year long.

Finally, in a Closed Loop system, you can either pressurize the system or not.  Not pressurizing the system is much easier to deal with.  For instance, if you have a tiny leak in the system, you can simply add a reservoir to the system and fill it every once in a while and not have to worry about it.  A pressurized system can have NO leaks in it.  Get a small leak in this and you have to fix it.

The issue with a non pressurized system is wear and tear on the pumps and increased energy costs due to the fact that the pumps have to work harder.  Pressurized systems have less friction while moving water through them.  Thus, the pumps do not have to work as hard reducing your energy needs.


What are these Loops?

A partial answer to this question is found in trying to understand what it does.  Loops generally circulates fluid in them for the GSHP to use.  It’s like a big underground garden hose that goes into the GSHP and out of the GSHP in one big… Loop.  Typically, they provide 1 ton of cooling (12,000 BTU’s).  So, if you need a Geo system that is based on your cooling needs, you can easily calculate the number of Loops that you need by understanding how big your A/C unit is.  If you have a 3 ton A/C unit that covers your needs, you will need 3 Loops for your Geo system.

A Loop is a section of pipe that is a certain diameter (typically ¾”) that is a certain length in size for proper thermal transfer.  Note: As I have read up on these Loops, it “seems” that the entire Geo ecosystem nomenclature is based on “tons”.  A ton is accepted as one Loop and a Loop is defined at certain pipe diameters and lengths.   The length of the Loop is defined by the medium (soil, water) that the Loop is running through

The questions that you will need to answer are:

             Is this going to be maximizing heating or cooling?

             Is your current system right sized for your home?

             Too much or too little cooling or heating?

             How many tons (Loops) are you going to need?

             Open or Closed Loop?

            If Open…

Will the source be able to provide a year round water draw?

Note: An Open Loop system requires the GSHP to have Cupro-Nickel Metal internals in order to handle poor water conditions of your water source.  Your GSHP dealer should ask you if this is an Open or Closed system and then make sure you get the right model.

            If Closed…

                        Ground installation

                                    How deep?

                                                The further down you go, the less radiant heat affects the system and

                                                            the more expensive trenching or digging gets.

                                                Where is the frost line?

                                    How long? 

                                                This depends on the type of soil/pond/stream that you have.

                                                *Ask neighbors with a similar setup what they did and how long

                                                            their Loops are.

                                    Will you need a drip tube to keep the soil moist?

                                    *Note: The Loops have to be separated vertically and horizontally.

                                                Again, ask the neighbors what they did or look it up on the Internet. 

                                                I used 20 inches of vertical separation.

                        Pond Installation

                                    Is the pond at least 8 feet?

                                    How long is the Loop?  (Typically, 400ft is good.)

                                    If silt builds up on the Loops, are the Loops long enough to compensate for

                                                decent heat transfer?

                                    *Note: The Loops have to be a certain distance from each other.  15’-20’ is


                        Stream Installation

                                    Does enough water run over the Loops for good heat transfer?

                                    How long will the Loops need to be?

                                    Does the stream have low volumes during the summer?



                                    How deep will the bore holes need to be?

                                    Will you go with a DX copper system for the Loops?

                                    *Your drilling company should be able to help you out here.


The bottom line is this…you need to try to maximize your assets.  What is the easiest, cheapest, and safest way to install the system for you?  In my case, I used my pond.

Once you get an idea of how you think you are going to proceed, start talking to local folks who already have system that will be similar to yours.  They can provide you with excellent information on what your system may require.  Did they need more heating or cooling in their system?

Once you start getting a good idea of what you think you are going to need for the Loops, start looking at HDPE (it’s GOT to be HDPE) pipe vendors.  Find a vendor that is willing to work with you on your installation.  This way, they can do a “sanity” check on your work.  IE.  Did you get the lengths and the number of Loops right?  Do not expect them to do hard core analysis work unless you are willing to pay them for that work.  You are asking them to look over your shoulder to do a sanity check not a full analysis.  If a pipe vendor works with you, do them the favor of giving them your business even if you can get a slightly better price somewhere else.

In my case, I have a nice chunk of property with a nice sized pond.  I could rent a trencher or bulldozer for the dirt or I could use the pond.  My main concern about the pond was destroying the fish by heating it up too much OR evaporating too much of it during the summer.  I like the fish and other creatures and I do not want to harm them.  Summer cooling will raise the temperature of the pond about 1 degree.  My pond has a general depth of 20+ feet which makes my installation pretty safe.  If you have a pond less than 10 ft, you might have an issue with these.  It just depends.   I’ve seen comments where ponds can be about 8ft and everything is OK. 

Having a contractor install my Loops would have cost me $10,000 for a simple pond / closed Loop install. 

My pond install was messy.  Covered later.  With a pond install, you can run shorter lengths of pipe.  For instance, I was cleared to run 400’ per Loop.  I dutifully coiled the Loop; but, then I learned late in the process that coiled Loops start getting covered by too much sediment and then heat transfer starts being hindered.  To fix this, you have to “re-float” the Loops every few years.  I think it would be just fine to put all of the pipe in at least 8’ of water (no coil) and run the same length of pipe as a soil install.  This way, when sediment builds up, the heat transfer starts acting more like a soil heat transfer instead of a better water transfer.  Just remember to run the longer pipe.

With my pond install, I suspended the coil portion of the Loop about 8” off of the bottom.  I should not have to re-float for a while and I ran a “dirt” install length… This means I could have run 400’ and instead I ran 600’ in the pond.  Since I ran longer pipes, my pumping costs will go up.  In this case, I had to get a two pump system for all four Loops.

An important part of the Loop is keeping the pipe buried to recommended depths all the way into the house.  What you don’t want to do is get cut corners by going to shallow or your pipes will run hot in the summer and cold in the winter.   

Kinking the pipes is akin to placing a shutoff value on the pipe.  The circulation will be poor at best and that particular Loop will be of little value.  If you kink a pipe, cut out the kink and fuse it back together.

For the Closed Loop system that can possibly freeze, the HDPE pipes should run a methanol or glycol mixture.  Your Pipe and Pump manufacturer can explicitly recommend which they would prefer.  I am running about 17 gallons of methanol or a 80% water to 20% methanol mixture.  The methanol will cost about $80.  Calculating a mixture of 20% methanol in ¾” pipe running at 2,900ft is something best left for an internet calculator.

Although methanol is toxic, it also plays a role in reducing the viscosity of the fluid.  The lower viscosity, the less work your pumps have to do.  I opted to go “toxic” on the “mixture” in favor of better heat transfer and less viscosity (lower friction).  As you opt to change the “toxicity” (more environmentally friendly) of the fluid mixture, you will also (probably) lower heat transfer capabilities and increase viscosity and henceforth increase pump costs.   You only need this if you have a Closed Loop system that is susceptible to freezing.  Warm climate Closed Loop systems do not need anti-freeze.    Again, use what the Pipe and Pump manufactures recommend.

Manifolds and Header Pipes…

Once you decide the previous questions, assuming you have a Closed Loop system, you now have to figure out where your Manifold is going to be.  On the inbound side, a Manifold collects all of the individual Loops into one place and then makes 1 run to the pumps.  On the outbound side, the Manifold takes the feed from the pump and disperses the fluid to the individual Loops.  So, you have an inbound manifold and an outbound manifold. 


This is a picture of the individual Loops coming into the manifold.  You have ¾” pipes feeding into a manifold with a 1 ¼” opening … and vice versa…  The pipe coming from the top of the opening will be the header pipe.  This will go into the pumps. 


This whole setup would have been better to be built by the pipe vendor.  Mine is OK and works great; but, it needs a little polish.  Note:The pipe coming out of the pumps (to the right) were replaced with different hose.


The pipe between the pumps and the manifold is called the Header pipe.  In my system, I tried (very hard) to run the Loops directly into the house and have NO fusion welds in the field for a Manifold.  Thus, the Manifolds and the Header pipe would all be in the house and I could watch for leaks.  I could feel very safe that nothing in the field was screwed up.  In this case, I had to fuse pipe in the field; but, kept the Manifold and Header pipe in the house. 

By keeping the Manifold and Header in the house, you are drilling more holes in your foundation for the individual Loops.  I have 8 small holes instead of larger holes for the Header pipe in the basement floor.



The concrete drill.  The paper on the wall was showing me where the manifolds are going.  I quickly changed my mind.


Fusion Welding and HDPE Pipes…

HDPE pipes are really the only types of pipes you want for a Geothermal application.  They are heavy duty, long lasting pipes.  Most of them are rated for a 50 year lifespan.

In order to “connect” these HDPE pipes together, you have to heat fuse them.  Heat fusing is a process by which you melt the HDPE pipe at a temperature of 500 degrees Fahrenheit for 10-30 seconds and “press” them together.  You need special equipment to do this and you need to be Certified in Socket Fusion Welding.  There are other types of Heat Welding; but, you will probably only do Socket Fusion Welding.

Certification for Socket Fusion Welding is pretty cheap ($50 typically) and very quick to do.  I was Certified in about 45 minutes.  Probably a bit too quick; but, I learned pretty quickly in the field what to do and not do.

For me, any weld that didn’t look perfect, I cut it off and tried it again.  In fact, only one of my fuses leaked after installation was completed.  (I have over 100 fuses.)  I had the most issues with the HDPE to Brass connectors.  It was my Brass fittings that leaked.  (There are fittings that allow you to fuse HDPE to a Brass fitting.)

I got a nice little burn from not wearing long sleeves.  I always wore goggles and gloves while fusing. 

The fusion tool looks like a short steel paddle shaped like a wooden paddle that you would see at a frat house.  The paddle heats up like a curling iron.  You will have a male connector on one side and a female connector on the other side for fusing the HDPE pipes.  You put the male and female portions of the pipe that you are trying to fuse on correct side of the paddle.  The pipe is designed to want to “push away” from the paddle, so you have to apply pressure to keep it on there once you begin heating the pipe up.  You time the length of time it stays on the paddle (10-30 seconds) based on the diameter of the pipe that you are fusing.  Take it off and push the two sides together and then inspect.  Note: The time that I used is for “ballpark” figure only.  This gives you an idea of what is going on. 


From the Top, Left, Center is the Fusion Tool (the Heater), the little silver Cups are the chamfer tools (these debur the pipe and provide a depth guage while fusing), and the Cold ring Tool (right in front of the tool box) is used to hold on to the pipe when heating.  In the tray are the “elements” that you screw on the Fusion Tool to handle the Male/Female connections on the HDPE pipe.  As you can see, a decent rental kit will have all of the sizes that you need.

Characteristics of the “fuse” can show you if it was a good fuse or not.  Too much or too little time on the paddle is going to mean a bad fuse.  Your class work will show you what a good fuse is.

Fusion welders cost about $50 a day and can be hard to get locally.  Fusing goes really fast, so you may only need it a day or two.  These paddles are $600 a pop, so the rental places will want a deposit.  These paddles come with tools that help you hold onto the pipe while it is heating and helps you set the depth of how much pipe you need to fuse.  You will need to clean and debur the pipe before each fuse.  This is in fact an easy thing to do.  


This fusion welder allowed you to put another handle on it.  The grayish circle in the middle of the heated square piece is what you put the female pipe connection on.  You can see remnants of the old ventilation system outside along with the old hot water heater.


This is what the fusion weld looks like from a side view.

We were fusing the manifold together… piece by piece.    It’s difficult to see; but, there is a small thermometer on the upper left edge of the welder.

Although fusing straight pipe is very easy.  One day when I was doing a LOT of fusing, I almost ran out of a certain “joiner” part.  When you are ordering your pipe, order all of the do-dads and throw in extras knowing you will screw a few up.  Also, when you start fusing, make a few practice runs to get comfortable.  You don’t want to run out of do-dads and increase your rental costs.

The Manifolds… 

The Manifolds got VERY interesting and this is something that you may consider having a vendor fabricate for you.  On the individual Loop side of each Manifold, I put shut off valves.  On the individual Loop side of the intake Manifold, I also put a pressure/temperature (p/t) port.  If you screw up a fuse on the manifold itself…  you have to throw it away and start over. 

When you put together the p/t ports and the shut off valves (Brass fittings), you have to screw these things together first (hope that you got it tight enough) and then fuse them to the correct “facing” orientation on the rest of the Loops.  You run the risk of a leak in the Brass connection after you fuse it and you can’t tighten things up after the fact.  Also, you can add more brass for connects and disconnects; but, you add more places for potential leaks.  If you screw up a weld on the Manifold itself, throw it away and start the process again.  I really worried about screwing up the last weld in a series of 22 critical welds.


The manifold to the right has the pressure / temperature ports at the bottom of them.  There is a little screw cap at the end that a probe is inserted into.  The green handles are shut off valves.

I think I over engineered the system by adding the shut off valves and p/t ports.  I like the fact that I added them; because I can take a Loop offline if it fails and I can individually monitor the temperature of each Loop… but, it was kind of expensive and complicated.  Also, if I find a Loop running “hot”, I can close the valve a bit to regulate flow.  If you have a Closed Loop, pressurized system, you absolutely need at least 1 p/t port to monitor you pressure.  Many times your GSHP will have such a fitting.

Into the house, I dug 5’ (OK, 4’ 10”) down right next to the house (under the foundation) and about 6” under the foundation of the house.  The HDPE Loop pipes come into the house up through the basement floor, an inch right inside the wall.  This is where using a header pipe and manifold in the field make drilling two holes in the concrete is easier than 8.  On the wall where the pipes come in, the manifolds collect and disperse the ingoing and outgoing fluid.  The wall was covered with 1 ½ plywood to easily and safely mount various devices (in/out manifolds, pumps, valves, electrical connections, etc…). 


Fusing the last set of Loops going into the house.  The was hot, dirty, and very cramped.


Zach is holding the welder and Sam and I are pushing the connections together on the welder.  At that point, we finishing timing the weld, Zach is lifting it out and Sam and I are pushing the fused ends together.  They have to be held together for 30 seconds.  It’s 90 degrees outside and the welder is 500 degrees right next to our faces.  Fun stuff.  I’m tucked into the hole going into the foundation of the house.


Is this over yet?  If you notice the date, it’s almost September and most of the inside work has not progressed very far.  The Loops are resting comfortably on the surface of the pond.  The gut is a little disgusting there... I've lost 20 piunds since then...  I need to loose a few more.

Typically, with HDPE pipes, the Loops are ¾” and the Header pipe is 1 ¼”.  Fusing ¾” pipe takes 10 seconds.  Fusing 1 ¼” pipe takes 20 seconds.  Some folks use ½” pipe for the Loops.  A Loop defines a ton and the diameter of the pipe helps define a ton.  I understand that ¾” pipe is the “preferred” size of pipe to go with.  (Bigger is better…right?)  The diameter of the pipe also dictates the amount of fluid that can travel through the system.  At the GSHP, you start dealing with another metric and that is Gallons Per Minute (GPM).  The pipe diameter affects how much fluid you can deliver to the GSHP.  The GSHP does not care about tons directly, it cares about GPM.  GPM is dependent on the number of Loops and the diameter of the pipes in those Loops.

Your tonnage (Heating or Cooling needs) will define how many Loops you have and the type of GSHP system you will need.  Make sure your Loops can actually deliver the requisite GPM if you decide to go with small diameter Loops.

Before you begin to fill in the dirt over the pipe, you have to run a pressure test, if you have a leak, you have to fix those places.  You might consider spending some money to get something to pressurize the pipe and be able to cap the ends of those pipes.  Those items can get pricey; but, very helpful nonetheless.  If you decide to do this over a longer period of time, being able to cap and pressure test the Loops before closing up shop for a while can give you peace of mind that the Loops are an area that you do not have to revisit.  These would have been helpful to me.

Note: When I fired up my system after being told that there were no leaks in the Loops (the contractor who installed the unit), I covered up half of the field welds.  A few days later, I noticed a small pressure drop.  The same with the next day and then the next day.  My only salvation in this case was to begin turning off the Loops and isolating the leak.  This was a big bummer.  So…  after some quick checking, I decided that I could run enough fluid through the 3 Loops AND have enough length in the field to handle proper heat transfer…. I think.

If you lay the pipe over rocky soil, the pipe may fail over time.   You want to carefully hand fill the first foot or so when covering up the pipe.  You have to keep the pipes separated by certain horizontal and vertical distances.   The job of burying the pipe is important, so do not skimp on this.  The pipe vendors should be able to give you good guidelines.

Once you have your Loops installed and tested, you’ve already knocked off a good chunk of the system.

Technically, my Loops are oversized for my heating and cooling needs.  My Loops are only required to go 400’.  I have 4 (really only 3 Loops now) Loops running 750’.  Minimally, I needed 1,600’ of pipe and I actually have 3,000.  Why?  I avoided (for a long long time) the need to re-float the Loops.  Note: This is a case where knowing a few more things before I started would have been nice…  (There is story there; but, it all worked out in the end.) 

Oddly enough, once you have the Loops in and tested, the rest of the work can go very very quickly.