T&T: Vented loop

[Steve Sipe]

Al Thomason wrote:
> The Vented Loop should go after the intake water pump, but before the 
> bowl. Cut the hose from the outlet of the intake water pump (not the 
> waste water discharge side!), run it up high to a vented loop, then 
> back down to the inlet of the bowl.
>
> This way the vent will be able to open under a vacuum that is a result 
> of a failure mode (e.g., water siphoning in), vs. were it is currently 
> installed and the normal action of pumping in water presents a vacuum.
>
> -al-
>
>
In part, yes it sounds right. However in reality, the inlet of the pump 
is below the waterline, and the discharge of the pump only goes to the 
rim of the bowl. By eliminating the vented loop on the pump suction, the 
flushing problem is corrected, but in the event of a failure of the pump 
or its related seals, the protection of the loop would effectively be 
lost, so I may as well plug the vent. If I planned on keeping these 
noisy (Jabsco) heads, I'd probably connect the vents to a normally open 
solenoid that would close during flushing. Still would have the problem 
with removing the air allowed into the top of the loop, but it would 
help. But since I plan to change them after some other more pressing 
items are crossed off the bug list, I think I'll just opt for masking 
tape on the vent inlet while we're aboard, remove it when closing up to 
go home. It's simply a less than optimum application. Best solution all 
round is a freshwater flush- vented loop problem solved!

Pump suction and air admittance just don't play well together.

Thanks all for the suggestions.

Steve Sipe
43 Solo "Maerin"
Upper Chesapeake