Steel holding tank disposal

[catlotion]

hi Everyone,

We're trying to eliminate some odours in our 1986 Beneteau and have decided to rip out the old toilet/holding tank system. It has a stainless steel holding tank which is prob around 15 years old. There doesn't seem to be any real leaking but there is a musty smell in the boat we can't get rid of. I understand steel tanks are not recommended so we're planning on replacing it with a Tek-Tank or similar.

I was wondering - does anyone have any tips for getting rid of the old tank? It's prob worth a bit to a scrap metal dealer but can't imagine anyone would want to take it. I don't want it in my car and I imagine they'll stop me putting it in the skip at the local tip anyway...

free to anyone who wants it!

Toby

 

[PCUK]

Can't see how changing the tank is going to solve the problem. Only reason for not having a steel tank is corrosion and that doesn't apply to stainless. I'm sure there are plenty of local owners who would love a stainless tank for many other uses.

 

[MoodySabre]

It is either leaking or it isn't. If it isn't then why replace it? The smell is probably from the hoses anyway. I'd try the easy answer first.

 

[PCUK]

I'd agree 100%.

 

[Tranona]

Yes, just been discussed on a long thread lower down. Although plastic is preferred to stainless, if your tank is in good condition, get it cleaned and pressure tested and re-use it. Change the hoses for best quality sanitary hose from Lee San or ASAP , make sure you have a big (at least 1") vent and your smells will go away.

 

[catlotion]

I was accepting the consensus that stainless steel tanks suffer from weld corrosion due to exposure to effluent. I've also read that steel tanks used for toilets have pretty short lives..?

I would expect any seam weld degradation to result in leakage of odour first before any liquid leaks out?

 

[Tranona]

You should be able to tell if a weld is potentially failing by cleaning and visual inspection. Then pressure test. Smells almost always come from poor ventilation or permeable hose, rarely from tank leaks. A new tank is going to cost you £500+ if it is custom made, whatever the material. Find a competent SS fabricator - one that does work for the agricultural or food industry would be good to check your tank out. I recently had a 120l SS water tank repaired on a small weld, inspection hatch put in and 4 new brackets welded on for £150. Put the saving into buying the expensive sanitary grade hose.

 

[prv]

Only reason for not having a steel tank is corrosion and that doesn't apply to stainless.

If you think stainless never corrodes then I have some rudder bolts you need to see!

The boat we've just bought (offer accepted this morning!) has a stainless holding tank which has visible corrosion round the welds. Don't *think* it's actually leaking liquid yet, but the old survey we saw mentioned a strong sewage smell in the locker (tank has since been washed out).

Taking this tank out and disposing of it is high on the jobs list. I'll almost certainly take it to the council tip - I don't know a local scrappy and it's not big enough to be worth the effort of finding and dealing with one. Can't see them objecting to me chucking it into their ferrous metal bin.

Pete

 

[PCUK]

Stainless doesn't corrode if used properly - and underwater in an oxygen shielded situation is a recipe for crevice corrosion. Totally different scenario!

 

[vyv_cox]

The primary cause of corrosion in welded stainless steel tanks is the incorrect selection of materials, both the sheet and the filler. The sheet should be 316L, where the L stands for low carbon. The filler rod should also be low carbon but will have a slightly higher content of the chromium, nickel and molybdenum making it more noble than the parent metal. Not many crevices in a rectangular tank, unless it was cheaply made.

 

[Tranona]

But in a holding tank situation welds (not the steel itself) are known to corrode, leading to leaks - worse than in water tanks. Plastic is superior for a holding tank.

 

[vyv_cox]

But in a holding tank situation welds (not the steel itself) are known to corrode, leading to leaks - worse than in water tanks. Plastic is superior for a holding tank.

As I said, not if it has been made correctly. Many welders use a standard rod that will be anodic to the tank metal. There are many elderly stainless steel holding tanks that do not suffer corrosion. I don't disagree about the plastic, though.

 

[Tranona]

As I said, not if it has been made correctly. Many welders use a standard rod that will be anodic to the tank metal. There are many elderly stainless steel holding tanks that do not suffer corrosion. I don't disagree about the plastic, though.

That is why I am suggesting there is no need to change the tank if the welds are sound and it does not leak. If a new one is needed, plastic is better.