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(no email)
Date: Mon Jun 02 2003 - 21:25:07 EDT
> Colin
>
> Unfortunately, I have to have the valve horizontal in the bilge, because I
don't have a
> deep bilge. However, let me understand what you are saying.
>
> Are you saying that when it is whirring, it is actually pumping water,
i.e. forcing water
> against the check valve flap, but the flap is sticking ? It seems to spin
much more
> quickly than when it is actually pumping. How much pressure do these Rule
pumps exert in
> a 1.5" hose ? Not enough to push open the flap ?
>
> Also, on the other side of the flap is the pressure of the residual water
in the hose,
> i.e. the water that doesn't get pumped out. I guess that would increase
the pressure the
> pump has to exert to get the flap open ? I wonder how I can calculate
that. I think it
> must be quite a lot. I have a U in the hose to stop sea water from getting
back in. I
> guess the top of the U must be 3' to 4' above the hose, about 12' away
from the pump.
>
> But how do you explain the other night when I switched to manual and it
only whirred. So
> I stopped, then started again, and this time it pumped ?
>
> It's a Guzzler 1.5" check valve. Maybe I should just use a bronze valve
with no spring ?
> The residual water would keep the flap shut.
>
> I appreciate your thoughts. (Your combiner is still working wonderfully.
This spring I
> ran tinned wire from my Statpower 20 amp charger to both banks of
batteries, as you
> suggested last year. Works well. Thanks.)
>
> Cheers
>
> Mac
Hi, Mac.
Yes, in fact your statement proves the point. A centrifugal pump will run
faster when blocked as do many devices of this style. Block off the inlet
to your shop vac when it is running - it speeds UP. Although this seems
contradictory consider that if there is no water being elevated, then no
work is being done on the water except for stirring it up. The stirring
part is just about constant but the work involved in raising water is not so
if you don't have to raise it, the load is less and it speeds up.
This doesn't PROVE that it is the check valve, just that the pump is running
and primed and trying to displace water.
This style of pump is designed to move maximum volume. The design is
contradictory to one designed for higher pressures. They are therefore very
limited in pressure available to crack open a check valve, in particular, a
check valve that was designed for a pressurized system where ":cracking"
pressure was not a serious design consideration.
These pumps, however, should be able to handle a lift of 6 to 8 feet not
counting the check valve, so they should be able to overcome the head
remaining in the column. Starting and stopping the pump can perhaps wiggle
the valve and help it crack free. I'm not directly familiar with the
guzzler valve but it should be satisfactory if made for bilge pump
applications, but all valves stick and the Guzzler manual pumps have plenty
of pressure to spare so it may not be suitable for an electric pump.
I guess the head of water would keep the flap closed if the bronze flap
valve was mounted horizontally and if there was no head, then it doesn't
matter if it didn't seal.
Often greater reliability can be achieved by switching to a 3/4" hose up to
the top of the "U", retaining the 1.5" for the remainder. True it will
restrict flow somewhat but increase reliability by an order of magnitude if
you can eliminate the valve. This hose will have only 25% of the flow-back
volume of the 1.5" hose and the residual may now be acceptable. Do you want
a gusher that works sometimes or a pisser that works all day?
I'm currently designing a "Bilge Pump Run Time Extender". It is a small
module set in epoxy that you connect across the existing terminals of the
bilge pump switch. When the float switch turns off it keeps the pump
running for an extra 60 seconds to pump right down to sucking air - lower
that you could reliably install the float switch threshold and maintain
reliability. It also allows the float switch to be mounted a little higher
so it doesn't re-cycle on flowback yet still empties the bilge. Market
researach:- Does anyone think this would be a viable product? It should
retail discount for about $49.95.
Finally check out my design for a highly reliable vented loop if you haven't
already seen it. http://www.yandina.com/hints.htm#Siphon I've had 6
running for about 14 years now without a single failure and zero
maintenance.
Colin Foster,
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