Bulkhead holding tanks

[ean_p]

Hi Peggy
Just a quick question........whats the best material to make waste holding tanks from please?

regards

Ian P.

 

[HeadMistress]

The recommended material is rotomolded polyethylene with a minumum wall thickness of 3/8"...welded PE is the next best choice...the materials are good, but the quality is entirely dependent on the skill of the welder. Polypropylene is ok, but must be welded...and again, dependent on the skill of the welder. However, PP is easier to weld than PE.

NO metal of any kind is suitable for waste holding...urine is so corrosive that it eats through welds in an average of 2-5 years, and even thick 316 stainless within about 10 years.

Bladders aren't much better...they only have an average lifespan of about 15 years, and more prone to stink than any other tank.

Fiberglass is a better choice than metal or a bladder, but is subject to any problems--blistering, rot etc--that a FG hull is likely to develop...except unlike a hull, the problems are on the inside of the tank, so not likely to be noticed till they've become VERY serious. Plus, FG weighs a lot more than PE or PP.

 

[Guest]

I never said the filter got wet. It is a large plastic inline filter unit which I fill with activated charcoal every month or so. It does not get wet but condensation does make it a bit icky when refilling so I wash it out.

It costs pennies per refill (large bag of charcoal) and it stops all those natural smells getting blown to the cockpit when the loo is pumped. I have never smelt hydrogen sulphide from it even before the filter. That might be due to the loo pumping a lot of air through the tank on each activation.