There have been so many replies that I'm not even gonna try to sort through all of 'em...I'm just gonna start from scratch to answer the question.
Originally Posted by AllezCat
So I have a vacuflush head
and Sealand holding tank system in the bilge
There are 2 independent thru hulls:
One line is form the head to thruhull #1;
The other line is from the holding tank to thruhull #2.
But, both 1 1/2" head hoses run from the bilge
amidships aft, then up above the waterline directly below my pillow.
It really stinks. probably from the previous owner(can't be from me).
So I intend to reroute the lines forward under the bathroom vanity(same height).
This is going to be a shitty job.
Just wandering if the above waterline loops are even necessary?
Also while checking this I found the vent line runs downhill before exiting somewhere(still looking)...This could be a problem too, yes/no???
thanks for your help...
No vented loop is in needed in any head discharge line that goes only to the tank. However, one IS needed in any line connected to a below-waterline thru-hull. So you'd need one in the line from head #1 and one in the line from the tank to thru-hull #2...that one goes AFTER the pump, between the pump and the thru-hull.
Vented loops should have an air valve in the nipple that only allows air INTO a line to break a siphon...nothing out. Air valves are replaceable parts
that have a lifespan and also need periodic cleaning
. So if your vented loops are squirting or outgassing, tend to the air valve instead of going through the agony to reroute hoses. That is, UNLESS you can shorten the runs considerably by rerouting the hoses and moving the vacuum pump(s). Then it's worth doing.
And it may be helpful to understand just how a VacuFlush works. The accumulated suction only moves the bowl contents as far as the vacuum pump...then the vacuum pump does two things simultaneously--it pulls the air out of the system between the bowl and the pump while it pushes the flush the rest of the way to the tank or thru-hull. How long the pump runs depends on the distance from the bowl to the pump...the shorter that is, the shorter the pump run time. If that's not long enough to push the flush all the way to the tank or thru-hull, it's gonna sit in the line till it gets another push from the next flush.
Hopefully that will help you decide whether you need to move any plumbing--whether you SHOULD or not...and where to put it if you do.
It's also possible that your odor
is caused by permeated hoses...if so, the only cure: new hoses. The best on the market today is Trident 101/102 Trident Marine: Sanitation Hose
(identical except for color). It's a double walled rubber hose that's been on the market for more than 15 years without a single
permeation failure...something that cannot be said about ANY other hose including SeaLand OdorSafe...I've personally been on half a dozen boats on which OdorSafe has failed and heard of dozens more.
About the tank vent line...a slight downhill run to vent thru-hull isn't the best idea, but isn't a problem unless the vent line is longer than a couple of feet and the "hill" is more than just slight.
This isn't the most fun job, but it doesn't have to be THAT bad if you'll take the time to pump out the tank and then thoroughly rinse out the whole system by running GALLONS of clean water through it. Catch any spills by putting disposable foil pans or trash bags under fittings.
I think that about covers it...