Save-A-Boat - The Forum for Plastic Classic Rebuilds!

In the middle of my holding tank installation, I need to install a vent from the top of the tank to the ouside of the boat. Can I use one of those neat SS gas tank vents thru the cabin side?

Also, as a Porta Head man all these years, I'm about to get initiated into the field of pumpouts. Does my pumpout hose have to extend to the bottom of the tank, or does the normal marina pumpout facility have it's own 'dip' tube?

The pumpout hose is basically just a hose. You need a dip-tube (or the hose needs to come out the bottom of the tank), and when you find a good source, let me know. I'm a few months behind you on the same job.

Since I'm in the middle of a similar project I'll chime in.

I decided to suck off the bottom of the tank (I have a top and bottom port pre-installed in the Todd tank) with a bit of a j-trap to facilitate getting as much of the sludge out as possible. The tank is also mounted with a very slight tilt towards that port. I'm hoping to, although haven't gotten that far, to run rigid PVC tubing for most of plumbing thus eliminating most of the odor permeation of flexible tubing. Perhaps I'm missing something though and that idea won't work.

As for vents, I keep reading you want two big ones. This facilitates the growth of aerobic bacteria which doesn't smell like the anaerobic variety. I even noticed a $200 air pump to help this at Fisheries(Sweet Tank). I had been thinking about trying to modify a fish-tank air pump for this (making a ac variant run off of dc--should just need a pulse at x hertz to the solenoid...) which would cost a good deal less and be a fun project that wouldn't involve fiberglass dust.

The other note on the vent line is make sure it is big enough so your tank isn't collapsed when you go to suck out the waste. I've never seen this happen but it sounds like it would be fun. Although I'd guess I'd prefer a collapsing tank than an exploding one...

For protection from tank implosion during dock pump out I recommend http://dometicsanitation.com/productpages.asp?pid=68 . It is a one way valve, it only opens when you develop a partial vacuum inside your tank because you regular vent can't keep up. Dock pump outs are fast!

Dometic Sealand also makes a dip tube kit http://dometicsanitation.com/productpages.asp?pid=64. Anyone who has read my other comments about head systems knows I am a fan of top of tank penetrations only.

Dometic Sealand Vacuflush systems are only available through authorized dealers, but West Marine is allowed to carry some of the plumbing fittings. I have never verified it, but these two pieces are likely available, though they may need to be ordered.

Hmm, I just noticed that Dometic has finished phasing out the use of the Sealand trade name. They bought out Sealand a few years ago.

Peter wrote:Can I use one of those neat SS gas tank vents thru the cabin side?

Yes, I often use that exact fitting. I would try to keep it as far from the cockpit as possible though. You could also add a http://dometicsanitation.com/productpages.asp?pid=67 if you really want to avoid the possibility of odors.

Thanks Dave,
That's exactly the information I was looking for!