Posted by Jim Wilkins on June 23, 2009, 10:14 am
> ..
> It just needs a vent, like any water system. You need to identify any
> potential airlock points, high-points in the pipeline where air can
> accumulate, and fit a small open tube (big enough to pass an air bubble,
> about 1/2" if it's straight up, more if it is a gradual gradient)
> leading as straight as possible from the top of the pipe to above the
> head. Otherwise, even without leaks there is the risk (certainty) of
> small bubbles carried in the flow accumulating there until a lock occurs.
> This of course won't work if it is a syphon, rising above the head. In
> that case you need to use a pipe section narrow enough to ensure a high
> enough velocity through the "negative pressure" zone to carry any
> bubbles down to a region of positive pressure, where they can be trapped
> and vented. This of course works against maximising your flow for power
> (and can be a problem if you are throttling the flow elsewhere, it'll
> run fine until you throttle back, then refuse to open up again). It is
> only in such areas of sub-atmospheric pressure that leaky joints will
> suck air in to the system. The suction can also cause gases to boil out
> of the water and accumulate.
> Tim Jackson
Vitruvius described something like this in Roman aquaducts where they
crossed a gorge on low pipes.
jsw
Posted by Tim Jackson on June 23, 2009, 1:33 pm
Jim Wilkins wrote:
> Vitruvius described something like this in Roman aquaducts where they
> crossed a gorge on low pipes.
>
> jsw
Oh, well, can't be original. Those aquarii were pretty clued up.
Ever read Pompeii by Robert Harris? Gets pretty close up and personal
with a Roman aqueduct.
Tim
Posted by wmbjkREMOVE on June 20, 2009, 11:38 pm
>I don't know why I never thought of this before. Turns out spa
>manufacturers use a lot of the same kind of hardware I could have used when
>making my hydro system.
The flex hose is really handy sometimes. If you use it with glue
joints, take more care with gluing than with rigid pipe. I've never
had any trouble, but I've heard of some who have. I'm thinking they
didn't use the correct glue though.
Wayne
Posted by z on June 21, 2009, 3:17 pm
wmbjkREMOVE@citlink.net wrote in
>
>>I don't know why I never thought of this before. Turns out spa
>>manufacturers use a lot of the same kind of hardware I could have used
>>when making my hydro system.
>
> The flex hose is really handy sometimes. If you use it with glue
> joints, take more care with gluing than with rigid pipe. I've never
> had any trouble, but I've heard of some who have. I'm thinking they
> didn't use the correct glue though.
>
> Wayne
>
So far i've just used barbed connections with hose clamps, but that
requires extra transition fittings. Man That site I gave has a lot of
ideas but I don't know about actually shopping there. 2" hose clamps are
6.95!! Makes me want to shop around
cheers
-z
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> It just needs a vent, like any water system. You need to identify any
> potential airlock points, high-points in the pipeline where air can
> accumulate, and fit a small open tube (big enough to pass an air bubble,
> about 1/2" if it's straight up, more if it is a gradual gradient)
> leading as straight as possible from the top of the pipe to above the
> head. Otherwise, even without leaks there is the risk (certainty) of
> small bubbles carried in the flow accumulating there until a lock occurs.
> This of course won't work if it is a syphon, rising above the head. In
> that case you need to use a pipe section narrow enough to ensure a high
> enough velocity through the "negative pressure" zone to carry any
> bubbles down to a region of positive pressure, where they can be trapped
> and vented. This of course works against maximising your flow for power
> (and can be a problem if you are throttling the flow elsewhere, it'll
> run fine until you throttle back, then refuse to open up again). It is
> only in such areas of sub-atmospheric pressure that leaky joints will
> suck air in to the system. The suction can also cause gases to boil out
> of the water and accumulate.
> Tim Jackson