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Hoses and suction, strange occurrence.

Old 03-05-19, 11:02 AM
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u235
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Hoses and suction, strange occurrence.

An interesting engineering dilemma I think I have the answer too.
I have a hose sitting on top of my pool cover down in the collected water. That hose is stretched out and the end is down hill. The hose is about 25 feet long, 1.5 diameter, and the ends are about 4 feet difference in height. Roughly 5 feet in the pool, 20 foot out of the pool. I always lean the distant end up against the fence about 8-10 inches to keep some water in the end of the hose so the hose never drains completely to keep air from going back up the hose. I leave it like this all winter. When I want to drain the pool top and assuming the hose stayed with the end up.. I walk out the hose starting at the pool towards the end and it burps and starts flowing and the cover drains. There is always enough water in the end to start the flow with some assistance. Last night about 3am I went out outside to check on something unrelated but I heard water running. Sure enough, the pool cover was draining itself. Although at a much slower pace than normal, it was coming out. I have no idea how this started on its own. It hadn't rained in 24 hours but there was a build up of water on the cover because I hadn't drained it in a while. I know it was not draining earlier in the day. The only thing that happened is it got extremely cold last night, down in the teens. hmmmm.. It seems the natural convection caused by the difference in pool cover water temperature and the end of the hose was was just enough. As the water left the pool, it cooled and became more dense and was the driving factor. Makes sense but not sure how it originally started unless the rapid cooling of the water in the end drew a slight vaccuum.

Last edited by u235; 03-05-19 at 11:18 AM.
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Old 03-05-19, 12:37 PM
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A large animal stepped on the hose.
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Old 03-05-19, 07:45 PM
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Was there any ice on the surface of the pool?
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Old 03-05-19, 08:16 PM
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3am?

There is a slight possibility you were sleepwalking and not in the backyard at all, but in the bathroom hearing the water drain from a different hose.
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Old 03-05-19, 08:57 PM
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Change in surface tension? Barometric pressure? There's a PubMed paper that touches on the effects but I don't have the patience to wade through it.
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Old 03-05-19, 11:58 PM
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Originally Posted by . Cranky . View Post
Was there any ice on the surface of the pool?
Yes. Started forming when the temp dropped. Tonight.. It's back down to the teens again, a thin layer of ice is there now and the remaining water was slowly coming out again.
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Old 03-06-19, 12:40 AM
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Originally Posted by u235 View Post
Yes. Started forming when the temp dropped. Tonight.. It's back down to the teens again, a thin layer of ice is there now and the remaining water was slowly coming out again.
Remember, water expands when it freezes... might be enough to start that "push."
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Old 03-06-19, 01:09 AM
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Water expands when it freezes, when it's heated... it's always expanding. It's gonna take over everything. We'd better drink it all before it gets any bright ideas.
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Old 03-06-19, 02:02 PM
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The pool and hose constitute the basis of a hydraulic lift. If you apply a weight over the surface of one side, then the water level on the other side will go up. I bet the weight of the ice on the pool was sufficient to push the water beyond the end of the hose and start the siphon.
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