Oly
Gold Supporter
It is crazy. Finished the piping this weekend. This is only my second summer of owning a pool. The water traveling through the filter system is unbelievable now. I had no idea this is how it was supposed to work 
I included another picture of the piping. Not super professional but it is getting the job done. I decided to do the main/skimmers and return since I was in there already. At the bottom left where the flex pvc is going back to the pool look above and you can see where I cut the main/skimmer flex pvc lines. The kinked main pressure return I pulled out was right next to those on the right. You can also see the concrete pilings I was talking about.
Now I just have to worry about freezing in the winter. I am doing the suggestion above. Backfill with sand to top of pipes. Then I have R-10 pink foam board to place above it, then back fill with the dirt on that. And make good and sure I get all the water out at winter closing. And probably some pavers above that. That's the plan anyway...
I included another picture of the piping. Not super professional but it is getting the job done. I decided to do the main/skimmers and return since I was in there already. At the bottom left where the flex pvc is going back to the pool look above and you can see where I cut the main/skimmer flex pvc lines. The kinked main pressure return I pulled out was right next to those on the right. You can also see the concrete pilings I was talking about.
Now I just have to worry about freezing in the winter. I am doing the suggestion above. Backfill with sand to top of pipes. Then I have R-10 pink foam board to place above it, then back fill with the dirt on that. And make good and sure I get all the water out at winter closing. And probably some pavers above that. That's the plan anyway...
Andy, I know this is an old thread, but I was just checking my YouTube channel and saw that you referenced my video of the inside of a damaged pipe back in comment #9. I'm so glad that helped you! I also checked out your YouTube video that you posted in Comment #11 and you were dead on! The chlorinator did the nasty! As you correctly observed, the closer the pipe was to the chlorinator, the worse the damage.
Now, I would like to address some of the other comments and concerns that I have read here, in an effort to help you understand better as well as to possibly help anyone else who may read this thread in the future while looking for some answers.
You were correct that the chlorine had weakened the pipe, but it collapsed from swelling, not from pressure from above. If either the pool or the shed were recent construction then I might be more open to considering that theory, but that pipe had been buried for over a decade. What happens is that, as the flex pipe swells in girth, it also swells in length! I have actually found pipes that have completely doubled back onto themselves in 2 places because of that, and that was even with them buried under all that dirt! So that is why the pipe was crimped and why the flow finally became too restricted.
As for the depth of the pipe in relation to the freeze line, that is not really much of a concern. You will find nary a pool construction company that buries their pipes below the actual frost line, and offhand I don't know of a single state in the US that has that depth in their requirements on new pool construction. The reason for this is because we aren't dealing with a water line that will be holding and tranporting water all year like a water main for your home would be. Pool lines get winterized. They rarely, if ever, freeze from above. Even in cases where pools haven't been winterized at all for years or plugs have failed, I haven'tcome across frozen pipes that were buried to the depth required in the state guidlines. In Maryland, they are buried 18"-24" deep, which is nowhere as deep as the frost line. And if the foam or insulation was needed then every pool built in your area would have that and the state would require it. However, the sand that you put around your pipes before backfilling was an excellent idea, though mainly because much of the damage I encounter to buried pool pipes comes from debris that was backfilled around them by someone who wasn't thinking or didn't know any better. Even with hard Sch40 PVC, concrete debris and stones can eventually dig their way into the side of a pipe from ground pressure coupled with the natural vibrations the pipe experiences while running.
(CAUTION: Shameless self-promotion -->) Just for reference, I have been building and working with pools since the late 70s and I have focused stricly on detecting and locating swimming pool leaks for about 25 years. In fact, my daughter and I (she is now running the company) are 2 of the handful of folks who teach leak detection to the pool companies at the industry conventions, and I have developed or helped with the development of many of the techniques and equipment that the industry currently uses as the standards for leak detection and location. All of that to say, "Been there, done that!"
~John
Now, I would like to address some of the other comments and concerns that I have read here, in an effort to help you understand better as well as to possibly help anyone else who may read this thread in the future while looking for some answers.
You were correct that the chlorine had weakened the pipe, but it collapsed from swelling, not from pressure from above. If either the pool or the shed were recent construction then I might be more open to considering that theory, but that pipe had been buried for over a decade. What happens is that, as the flex pipe swells in girth, it also swells in length! I have actually found pipes that have completely doubled back onto themselves in 2 places because of that, and that was even with them buried under all that dirt! So that is why the pipe was crimped and why the flow finally became too restricted.
As for the depth of the pipe in relation to the freeze line, that is not really much of a concern. You will find nary a pool construction company that buries their pipes below the actual frost line, and offhand I don't know of a single state in the US that has that depth in their requirements on new pool construction. The reason for this is because we aren't dealing with a water line that will be holding and tranporting water all year like a water main for your home would be. Pool lines get winterized. They rarely, if ever, freeze from above. Even in cases where pools haven't been winterized at all for years or plugs have failed, I haven'tcome across frozen pipes that were buried to the depth required in the state guidlines. In Maryland, they are buried 18"-24" deep, which is nowhere as deep as the frost line. And if the foam or insulation was needed then every pool built in your area would have that and the state would require it. However, the sand that you put around your pipes before backfilling was an excellent idea, though mainly because much of the damage I encounter to buried pool pipes comes from debris that was backfilled around them by someone who wasn't thinking or didn't know any better. Even with hard Sch40 PVC, concrete debris and stones can eventually dig their way into the side of a pipe from ground pressure coupled with the natural vibrations the pipe experiences while running.
(CAUTION: Shameless self-promotion
-->) Just for reference, I have been building and working with pools since the late 70s and I have focused stricly on detecting and locating swimming pool leaks for about 25 years. In fact, my daughter and I (she is now running the company) are 2 of the handful of folks who teach leak detection to the pool companies at the industry conventions, and I have developed or helped with the development of many of the techniques and equipment that the industry currently uses as the standards for leak detection and location. All of that to say, "Been there, done that!"~John