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Q: Syphoning water and stopping sphon ( No Answer,   3 Comments )
Subject: Syphoning water and stopping sphon
Category: Science > Earth Sciences
Asked by: rich12345-ga
List Price: $5.00
Posted: 18 Apr 2006 09:02 PDT
Expires: 26 Apr 2006 01:48 PDT
Question ID: 720194
I have an underground water tank at the top of a slope and want a hand
operated sytem to pull water vertically out of tank and for it then to
run down an enclosed pipe to bottom of slope but also to stop when I want
it to stop.

Request for Question Clarification by sublime1-ga on 18 Apr 2006 13:56 PDT

Once you get the downhill pipe 'primed', or full of water,
it will run until the tank is empty of the the water level
falls below the opening for the pipe within the tank. I 
don't see why you can't just put a faucet or valve at the
bottom end of the pipe, and turn it off before the tank is
emptied. As long as the pipe remains full of water, it will
resume siphoning when you re-open the valve or faucet.

Let me know where this takes you, and whether it satisfies
your interests...


Request for Question Clarification by sublime1-ga on 18 Apr 2006 13:57 PDT
Sorry, that should read, "it will run until the tank is empty
OR the the water level falls below the opening for the pipe 
within the tank."
There is no answer at this time.

Subject: Re: Syphoning water and stopping sphon
From: myoarin-ga on 19 Apr 2006 03:02 PDT
That is also my understanding.  One problem could be any air leaking
into the pipe, thus creating a bubble at the highest point which would
break the syphon.
Subject: Re: Syphoning water and stopping sphon
From: irlandes-ga on 20 Apr 2006 18:30 PDT
I am in the mountains of Mexico, where water is normally very
precious, and this year of drought even more so.  We do move water by
siphon, and we do put valves on the end of hoses to shut it off when
we have moved enough.

Let me mention priming.  On a small, short hose, one can simply suck
on the end, and start a siphon.

This can be a problem when the water is not drinkable, or when the
hose or pipe is too large for the mouth to pull it over the top and

So, there can be two ways of priming it. When a hose is used, I hold
the bottom end of the hose up a ways, but not higher than the source
of water itself, then pour a small bucket into the end of the hose.

When I think it is full, I toss it down hill, and if i did it right,
the water I put in it starts the siphoning process.

It would also be possible to put some sort of valve near the top, shut
the bottom, and pour water into the top valve, until the water
replaces the air in the  hose.

When you have done so, shut the top valve so no air can enter, then
open the bottom valve and the siphoning should start.

As they have said, when you stop it via shutting off the outlet valve
(we often use an ordinary faucet such as one installs for connecting
garden hose0 if there is no leak, it will start again later by simply
opening the valve again.

One common use here, I have an 8,000 liter cistern which fills over
many days from slow, low pressure village water system. When we poured
a new roof, it took a lot of water, so much that one hose would not
keep up with the men working. So, we put siphon hoses into the
cistern, and had several running at the same time, which just barely
kept up.

Actually, as far as a bubble stopping siphon, the siphon function is
induced by the weight of water falling down the hose or pipe.  If that
hose is long enough and has enough water in it, it will pull quite a
bit of air over the top and the water behind the bubble will keep it
moving.  This happens a lot. but, it does depend on the ratios of
water below v. the size of the bubble.  That's why sometimes when I
prime a siphon hose by pouring water in the bottom, it does not always
work the first time, if I don't put in enough, so I say some bad words
and try again.
Subject: Re: Syphoning water and stopping sphon
From: irlandes-ga on 20 Apr 2006 18:36 PDT
I had forgotten my roof lakes. In 1993, my wife's brother started this
house.  They were (no joking) all drunk by 10 am, and as a result, the
roof he built was very poor. It had sagged so far that when it rained,
there were "lakes" on it, three of them, holding maybe 150 gallons of
water total.

WEll, that is not a safe roof. Until we got money to demolish the roof
and build a new one, when it rained I would go up  there and get rid
of the water.

At first, I used a shovel or broom. That was too much manual labor, so
I got pieces of hose, one for each lake.  I put a piece in each lake,
laid a rock on it so it wouldn't fall off, and dropped the end over
the side of the roof.

When it rained, I would get a small bucket of water, stand below the
rood, and hold up the end of the hose, and pour water in the end of
the hose.  it was touchy, but if I got enough in there, when I dropped
the end of the hose, it would start siphoning the "lakes" until it got
so low the intake end of the hose would get too much air, then I'd
have to go up and sweep the remainder, which wasn't much.

The roof work I mentioned, was when we put up the new roof, and it is
so good there is not a drop of water on that roof after the rain
stops.  The man who built it for us has built 20 roofs a year for 26

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