Vented loops on Vacuflush

PascalG

PascalG

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came across something interesting yesterday (not on my boat)

boat with 4 Vacuflushes (nice electronic models where you press a little lever just like a home toilet sending a some water in before a servo motor opens the ball valve)...

Each head has a Y valve under the nearby sink (unlocked... yikes) and also had a vented loop between the vac pump and the Y valve. on a couple of flushes we smelled "something"...

seems to me that the set up is wrong and that when flushing one head to the holding tank, air could be coming out of the vented loop on one or more of the other heads.

There is no need for vented loops with VF going to a holding tank, only for overboard discharge. It looks like the loop should be AFTER and not before the Y valve to be totally out of the picture in normal near shore/inland operations.

doens't seem hard to swap it around, any thoughts before this goes on the boat to do list? Vic?
 
Yes, you're right Pascal. The only place a vented loop "might" be needed would be between the macerator pump (if there is one) and the through-hull fitting, if the holding tank is set up to enable pumpout while out to sea. If the macerator pump or the lines are below the boat's waterline, then it would be a good idea to add a vented loop for safety. Otherwise, there's no good reason to have a vented loop anywhere else, and it (they) would be just another source for a potential future problem.
 
yes, there is a macerator (sealand) and a vented loop on that line which is fine.

now, when you have Y valves for overhead discharge, shoudln't you have a vented loop between the Y valve and the thruhull? seems that it would prevent syphoning back although with VF water will not go beyond the vac pump/duck bills and certainly not past the ball valve.

would you suggest that these vented loop should be removed altogether?
 
A more normal setup for Vacuflush would be that all toilets discharge to the holding tank. The holding tank could have one outlet to a y valve or two outlets - one to macerator and one to dockside pumpout.

Is it possible that the y-valves and overboard discharge for each head are remnants from an old, manual system? Where are the vacuum pumps in the current set-up?
 
no, it's all factory done and labeled, on a fairly new boat... i'm guessing the direct overboard were installed for over seas markets. They will be closed, handles removed, Y valves ziptied, vneted loop removed... boat has a large hodling tnak with sealand..
 
how did the vacuum develop in a line with a vented loop?
 
the vented loop is after the vac tank/pump, between the vac pump and the holding tank.
 
then it must have a check valve because of the pressure so there shouldn't be any smell?????????? But why would it be there???
 
it doesn't make a lot of sense, unless mayb they offered different options for heads on the boat and some of them required a vented loop. with a VF, water cannot syphon back past the pump and even if it loose vaccuum, it will not get past the ball valve anyway... i know that the vented loop on my boat (for the macerator) is vented out to the main holding tank vent, it's not open to the interior of the boat.

minor bonehead flaw on an otherwise impressive boat...
 
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