Hello Paulespo, 25 feet of hose is what I have found it takes to clean the bottom of the Womb all the way back into that void section under the cliff face. Yes I used duct tape to secure the end of my inch and a half pool hose to the end of the aluminum, expandable pole that I used so I could just be on the surface of the pool looking down with my mask and using a snorkel so I did not have to keep putting my head above water to get a breath. Yes it is exhausting to keep diving down to the bottom of the pool and rather quickly you overheat being in the hot water. With an inch and a half hose it can go pretty slow if there is a lot of debris and algae, and a hose that diameter can get clogged rather easily.

Using 3 inch flexible hose would be much quicker at cleaning but keep in mind it will also lower the pool level faster with so much water volume flowing through it. Best to have a good solid, dependable connection for connecting your 10 foot sections together. Duct tape may not be strong enough for that. I think 20 feet will be a bit short so maybe bring another 10 foot piece, or a five foot section. Getting the siphon going on larger pipe like that is more challenging. You can't just easily put your had over the end to hold the water in the hose when you put it over the side to start the siphoning. So it will be helpful if you figure out a means to seal the one end with something that will hold until you get the one end over the side then you can take it off and start the flow. A larger hose is heavier when filled with water so it would be good to have a strong person or two to help with moving and controlling the hose while you work on the cleaning end of it.

That other black pipe you found by the Anniversary pool, I think you mean five inch ( your wrote .5 ), I don't know what that is for/about. Maybe someone used a piece to channel the hot source flow under the path, or it had something to do with channeling the hot water more effectively over to the cement dike above the Anniversary pool. People over the years have used sand bags, or shorter sections of hose to divert the hot water in that area one way or another. If you divert some of the hot water through the dike then the Anniversary pool can be cooled down at bit that way.

Regarding that smaller pool at the south end of the Anniversary pool, it has no name, at least none that I have ever heard from anyone. It does not get used much, is usually full of algae, so perhaps that is why no one has come to name it. My wife actually came up with the name for the Serenity pool years ago at a time when it had no name. There are post about the naming of it from years ago in the archives of this forum, or maybe it was the previous forum incarnation before this version. That small pool does not have a drain which would make it easier for cleaning. I have just used a cleaning hose to clean it at times which works fine but you have to do it quickly since it does not hold a lot of water and the pool level goes down pretty fast. About that pool. Many years ago there was no Anniversary pool. In its place was a large, thicker dirt and grassy bank. The hot source water flowed down in a dirt channel in the bank, across it to the Womb. Then one year there was massive flooding which ended up eroding a big portion of that bank away such that the hot source water after the flood was just running down the hill across where the Anniversary pool now sits.

Arizona Mike, a long time regular back then, worked with some other people and created the rock and cement dike going across the granite above the Anniversary pool. They built that smaller pool as a means to keep the hot water further contained and flowing down towards the Womb. It appears from the angle of the dike that without that additional little pool the water would have just run down the hillside from the south end of the dike, and not into the Womb. If you look at the layout next time you will see what I mean. Some years later a group of people constructed the Anniversary pool. I think most of the work was done in about a weeks time. You could look to see if there was a feasible possibility of creating a drain hole in is lower side of that smaller pool. A hole might be created with a hammer and chisel, cutting through the cement somewhere and then it could be sealed with a plug of some sort or by other means.