Hoping to get in the pool a little earlier than mid-late May this year...

I bought a black plastic garbage can at Lowe's, along with some 2" and 3/4" PVC and a cap and some fittings.

Drilled a 1" hole in the bottom of the trash can. Screwed a 3/4" threaded male adapter into the hole from the bottom. It fits so snug, no silicone needed. Constructed a bell siphon inside the can and attached it to the male threads. Coming out of the bottom, put an elbow and about a 4' long drain pipe that pours back into the pool.

The bell siphon is made like this: Bell Siphon Instructions

I drilled a 1.5" hole in the side of the trash can, above the high water line (as determined by the bell siphon riser) and fed the pool drain hose through it. inside the can, I wrapped the drain hose around a 3/4" PVC elbow with a short stub of 3/4" pvc sticking out of it, just to direct the flow downward. Used a spring clamp to keep the hose attached on the PVC.

The siphon works fine. I had to adjust the pool drain at the valve so the flow was less than the flow thru the siphon when it drains, so that the can didn't continue to fill. (i.e. so water out >> water in).

The siphon works a lot like this: Bell Siphon demo except my 30 gal can fills in about 30 minutes, and takes about 5 minutes to flush.

The whole shebang cost me about $20-25. Not sure how much heat it'll add to the pool water, I know there are more efficient ways, but they're more expensive and more cumbersome. This took a couple of hours, and the whole thing is easily disassembled. Since it's such a low pressure system, all the PVC couplings are just hand tight, no cement used.

Pardon my ignorance, but how does this heat the pool?

That remains to be seen. It's really pretty much an experiment. I'll run it tomorrow and measure the in and out temps when I get home from work. I know the black trash can will get hot in the sun, if it transfers just a little of that heat to the water as it runs all day it can easily add up to a few extra days or weeks in the pool.

I'll report back on the temps soon.

I don't think 55 gallons of 70 degree water will warm up a 10,000 gallon pool.

It'll be 60 gal. per hour. We'll see. Worst case I spent $25 learning to make a bell siphon.

The problem is the specific heat of water. You won't get water up to 70 with only 1 hour. Granted I have no idea what this bell syphon is, you still will have a hard time making a dent in the water temperature with only an hour, unless you get an outside heat source.

Perhaps.

Here's my thinking...

The water heats up because it gets some sun on its surface, plus whatever the pool floor absorbs (not much at depth, plus it's basically white). By pumping water into the trash can, I'm exposing more of the water's surface to the outside temps. How much more heat it'll get, we'll see. But this is the middle of march. Typically the water is comfortable for swimming around the end of May. If this runs 12 (daylight) hours a day, even an incremental increase in the heat gained could really add up over the next 2.5 months.

Normally I run my pump 24/7. Since I don't want the water being cooled in the barrel at night, I'm only going to run the pump during the daytime. My cost for this experiment is $25 minus whatever I might save on electricity, AND I learned something.

I think it will help. I'm not sure how to quantify that, but I'll check the inlet and outlet temps to the barrel. I'm sure there will be SOME difference.

People have reported significant increases in temp by running their pool water thru a long, coiled length of black tubing. Mine has a lot less surface area, but it's not nothing, either.

Why are you running your pump 24/7? Wasting a lot of electricity it would seem.

That's what the guy I bought the house from told me he did, so I kept it up. My first pool. I've come to realize it's not necessary, but plan to put it on a timer and haven't gotten around to that yet.

The generally accepted rule of thumb is that you need to run the pump long enough to turn over the water once a day, meaning passing the complete volume of pool water through the filter at least once. Most pumps are sized to accomplish that 2-3 times in one day if run continuously. I would cut it back to no more than 12 hours personally. You may be able to cut it down to 8 but start with 12.

we were mostly overcast today so no heating from the sun. will measure temps on a sunny day.

passive solar, we built a few small units at work years ago, not much ever came of them, though the folks that built them are long gone. At the very least, it may help bring the pool up to tolerable temps sooner for next to nothing.

I have no idea if this will work, but I always live a good experiment. Good for you trying this out.

buy solar pool cover (aka bubble wrap) online for 50-100 bucks. cover pool and wait. sunny days can raise the temp noticeably...
also, leave pumps off to allow for a "warm layer" of water and then run pumps for 6-8 hours to circulate warmer water. my pool isn't a deep pool, only a play pool but last year i was able to get 3 degrees of temp increase in one sunny day. it takes alot of gas and a large heater to do that the traditional pool heater way.

I bought one of these for my pool, so we can swim from March to October (roughly). Cranking it up this weekend.

i hope it is... there should be very little evaporative cooling in my case, since the water is contained until it reaches ~30 gal and then is dumped back into the pool.

It's not gonna work. Probably won't even change the temp a tenth of a degree.

Covering the pool with black plastic would probably work though.

My father in law built a pool heater. It was like a horse trough, bright chrome that got real hot. He pumped water out, down the trough in a think layer, then back into pool. The heater itself worked; the water leaving the trough was much warmer than going in.

However, it didn't heat a 15K gallon pool for chit.

He also tried laying out black plastic trash bags on the water. While it did warm the water beneath it, that warm water would mix with the rest and the efforts were futile.

Absolutely no need for a 24/7 pool pump. In the summer I run about 10 hours on high and winter about 5 on low speed to keep things circulating. Water temp is 70+ now so I guess it's time to add some chlorine tabs for the first time in months.

fill a metal trash can partially with diesel, float it out on the pool, set the diesel on fire, you're good