Hi, all! First, let me preface my first post by thanking everyone here for lots of help last summer when I first started pool maintenance on my own. I hadn't registered or posted, but lots of previously-addressed questions were exactly what I needed to learn about pool maintenance. I come to you now with a few questions, seeking advice directly...
I'll list some details about the pool first, since I know that's the most helpful first step:
It's an in-ground, gunnite pool, about 10,000 gallons. I live in San Diego, California. The pool has some cypress trees right next to it, and it frequently gets debris from the trees in the water. The pool has one floor drain, and one skimmer. The pump/filter sit about three feet above the water level in the pool, due to the backyard having a slight hill. There is only one pipe that comes up from the ground/concrete into the strainer basket, and has no valves inline between the ground and strainer. The filter is a Cartridge-style filter, installed about three years ago, which replaced a stainless steel DE filter tank. There is a valve after the filter, which diverts water to a bank of black plastic solar heater panels, or directly back to the pool. There are two return jets, which are just small plastic pipes, and don't have any kind of valves to open or close them.
Okay, so on to my problem. About a week or so ago, I noticed that the pressure gauge on my filter was much lower than normal, only 3-5 PSI. I then noticed that the strainer basket had air in it while the pump was running, creating quite a large 'tornado' of air/water. When the pump is off, the strainer pot is almost immediately filled with water, with only the very smallest air bubble at the top of the clear lid. So, I suspected an air leak, between the intakes and the pump. I removed the lid from the strainer and cleaned the lid gasket as well as the mating surface of the strainer. The gasket looks good - no bulging, not misshapen. With that replaced, I still got a lot of air in the strainer pot when the pump is turned on. So, I tried the method of turning the pump off and looking for a spurt of water, found nothing. Tried applying shaving cream to all the plastic joints, and found no leaks (to be fair I couldn't see underneath the pipes as the whole thing is inside a small wooden house and I don't have a proper inspection mirror.
So, unable to find a leak I kept googling with different search terms to maximize my results, and I came across a comment that a clogged skimmer line can mimic the symptoms of an air leak - namely, the air appearing in the strainer pot. Since I was unable to find a leak, I decided to look into the possibility of my skimmer line being clogged. I read that using a drain cleaning bladder could push clogged debris back out of a skimmer line, and that for especially stubborn clogs, the drain bladder could be applied first from the strainer, back towards the pool, and then applied from the skimmer towards the strainer.
I bought a rubber drain bladder from Home Depot and hooked it up to my garden hose and got it situated in the strainer pot, nozzle jetting out to the skimmer. I turned it on, and got water flow (though I'm not sure how much) and some bubbles coming out of the skimmer. No debris came out. So, I thought perhaps this is a stubborn clog, I'll go ahead and reverse the drain bladder to try and work the clog free. Here's where it gets interesting - I put the drain bladder in the skimmer line headed to the strainer, and turned on the water. The bladder filled up and wedged itself in the pipe as it should, but, at the strainer, absolutely no water flowed from the pipe. My first thought was that perhaps the line was connected somehow to the floor drain, and that the water jet was simply not impacting the clog. I shut the water off and went to remove thedrain bladder from the pipe, and discovered it was stuck fast. I simply could not remove it, and the bladder was still inflated. That tells me that the water pressure indeed found a clog and was completely cutting off flow from the skimmer to the pump, and that the only place it could be getting water from was the floor drain, and, in theory, not able to draw enough water through only the floor drain creating the air bubble in the strainer.
I had to remove the hose from the wall in order to release pressure on the drain cleaning bladder so that I could remove it from the skimmer. So, now that I've written an entire novel, my question is, does any of my reasoning hold up? Could my skimmer line be so clogged that it's creating what looks like an air leak in the strainer, and the low pressure in the filter?
If so, should I then find a pool service to use CO2 to clear the clog? I tried using the bladder from the strainer a couple more times with no debris being unclogged.
I very much appreciate any help/advice! I'm at a complete loss (I think. I might be on the right track, which is what I'm hoping to learn).