Aluminium holding tank - good or bad?

[Cashbuyer]

Conflicting opinions about aluminium holding tanks. More negative than positive (pitting, weld failure etc) so should they be avoided completely? Viewed boat at weekend with one installed. Whole boat had faint smell of sewage and was not pleasant. I have a feeling it could be pervading the tank walls. Loos compartments clean and well presented. Any thoughts?

 

[miket]

Common

Many boats with holding tanks smell a bit niffy. Very difficult to avoid.
Some say that the pipes used to connect loos to tank become slightly porus over time.
Lee Sanitation seem as good as anyone at solutions.

I once saw the state of an alu' water tank from a 25 yr old Princess 30DS. Not a good advertisement!

 

[DAKA]

My aluminium one also failed year 10-12 although I did manage to find it before it sank the boat.

loads of holes in it, once removed some were huge holes.

I replaced it with plastic although it would have been easier to remove it and repair it with sheets of aluminium I decided it was a sinking hazard as the condition of the base(where it rotted) couldnt be inspected.

It wouldnt stop me buying a boat with one fitted as long as the seacocks allow it to be isolated and bypassed.

 

[Deleted User YDKXO]

Sewage smells on boats usually come from one of two sources. Either the holding tank vent pipe is blocked preventing air from the holding tank being vented overboard or, more likely, the pipework to/from the holding tank has become porous. Many builders use standard bilge pump pipework for piping up toilets/holding tanks and this degrades over time especially on pipe runs where there may be a risk of stationary liquid in the pipe eg on near level runs of pipe. You can tell by getting a piece of paper kitchen towel and rubbing it on the pipes. If the paper smells, the pipes are porous and will need to be replaced, preferably with sewage quality pipework.
Yup, an aluminium tank is not ideal and it could also be a source of leaks/smells but replacing it with a plastic tank is not a huge cost so just factor a few hundred quid into your sales negotiations for the boat if you buy. Lee Sanitation are a good company to talk to about marine toilet and holding tank stuff http://www.leesan.com/

 

[AndieMac]

My aluminium one also failed year 10-12

We had a strong sewage smell in the 1997 model boat from 2005 and it just got worse, changed everything in the system from loos, pipes, charcoal filters to flushing the alloy tank (600 litres).
It was eventually discovered last year that the tank was leaking and needed repair or replacement, so out she came, which was major surgery, including the complete dismantling and emptying of the starboard cabin to use as a workshop because of the size of the tank.

The alloy internal pickup pipe had corroded half way up, so the tank would never empty due to lack of suction, resulting in more corrosion all the way around the 'waterline' created.
The old tank had to be chopped up (in the cabin) to allow it to pass through the cabin doorway, measured up and replaced in GRP, in pieces, moved into the cabin and glassed together before sliding down below decks into the bilge space.

 

[Cashbuyer]

Thanks guys

I as thought, not that good...