decommissioning a holding tank

[ChattingLil]

We are going to decommission the holding tank that is built into the keel of our long-keel steel boat. (for a few reasons, happy to elaborate if anyone is bothered).

We are going to install a new system.

Question: what would you do with the decommissioned one? Leave it empty? Fill it with something stable (we could do with the ballast there)? We will want to use the same breather hole for the new system - do you think it would be ok to T two breathers into one?

any thoughts from the gurus?

 

[prv]

We "decommissioned" a leaky old holding tank in Ariam's cockpit locker - by which I mean, I sawed through all the hoses and then hoyed it up out of the locker and over the side of the boat to my dad waiting below. Who, I later learned, wandered off and stuffed it in a general litter-bin!

That was a steel tank in a GRP boat - but it sounds like yours might be part of the structure? Need to know a bit more about it really.

My preference would be to take it out, but if it's welded in then perhaps clean it as far as possible and then fill it with gravel?

Pete

 

[ChattingLil]

We "decommissioned" a leaky old holding tank in Ariam's cockpit locker - by which I mean, I sawed through all the hoses and then hoyed it up out of the locker and over the side of the boat to my dad waiting below. Who, I later learned, wandered off and stuffed it in a general litter-bin!

That was a steel tank in a GRP boat - but it sounds like yours might be part of the structure? Need to know a bit more about it really.

My preference would be to take it out, but if it's welded in then perhaps clean it as far as possible and then fill it with gravel?

Pete

Yes it is part of structure. Steel. Unknown quantity I'm afraid. Would appear that bottom and sides are part of the keel. Top is a flat pan under the engine. Inaccessible access hatch (right under the engine). Inaccessible inlet and outlet pipes.

due to inaccessbility, we would find it nigh on impossible to fill with anything other liquids.

thanks for the thoughts!

 

[pvb]

due to inaccessbility, we would find it nigh on impossible to fill with anything other liquids.

Lead shot?

 

[prv]

due to inaccessbility, we would find it nigh on impossible to fill with anything other liquids.

I believe ships sometimes fill similar voids (what would be tanks, except that the ship doesn't need another tank) with grit. Pours in much like a liquid, and can be sucked out if later required.

Alternatively, how about filling it with oil? Having stored sewage in there I'd be a bit worried about the state of the steel - sounds like you can't access it to inspect or protect it, but submersion in oil should stop any further corrosion. I've heard of steel yachts having their rudders filled with oil since the inside can't be painted after welding the last panel on.

Pete

 

[VicS]

Give it a quick rinse out and use it as a water tank.

 

[NormanS]

As prv says, fill it with oil, absolutely full, then you don't need to worry about inaccessible steel deteriorating.
Guess that you would need to have separate breathers.

 

[prv]

As prv says, fill it with oil, absolutely full, then you don't need to worry about inaccessible steel deteriorating.
Guess that you would need to have separate breathers.

If it's full of oil, surely it doesn't need a breather? Just a screw-down cap somewhere (assuming you can't weld a lid down onto a tank full of oil!)

One for the experts - would it be ok for the OP to use used engine oil for this purpose? Should be obtainable free if you can find the right place, whereas a hundred litres or more of new oil would cost a bit.

Pete

 

[NormanS]

If it's full of oil, surely it doesn't need a breather? Just a screw-down cap somewhere (assuming you can't weld a lid down onto a tank full of oil!)

One for the experts - would it be ok for the OP to use used engine oil for this purpose? Should be obtainable free if you can find the right place, whereas a hundred litres or more of new oil would cost a bit.

Pete

Say the boat was ashore, and subject to a temperature a lot higher than it was when the tank was filled. The expansion of the oil would probably a lot more than any increase in the volume of the tank. Might be safer with some form of breather, or expansion tank.

Old engine oil might be acidic, but used gear oil would be ideal.

 

[Scotty_Tradewind]

1. Fill with oil with a breather.... have a knock down and where does the oil go?

2. Clean out, spray with light oil.... fill with liner and use as a water tank.

3. Fill with steel/lead shot and spray with light oil to stop rust.

4. Clean out, derust. prime and use as storage.

5. Clean out and use for importing.......

S.

 

[xyachtdave]

Give it a quick rinse out and use it as a water tank.

Comedy gold VicS!

 

[david_bagshaw]

Clean and convert to a fuel tank?

 

[NormanS]

1. Fill with oil with a breather.... have a knock down and where does the oil go?


S.

Wow! Does that mean that none of us can have fuel tanks?

 

[ChattingLil]

1. Fill with oil with a breather.... have a knock down and where does the oil go?

2. Clean out, spray with light oil.... fill with liner and use as a water tank.

3. Fill with steel/lead shot and spray with light oil to stop rust.

4. Clean out, derust. prime and use as storage.

5. Clean out and use for importing.......

S.

Clean and convert to a fuel tank?

the holding tank is completely inaccessible. If we could do any of the above we could probably service, repair it and use as originally intended

 

[Lucky Duck]

How about filling it with ready-mx concrete?

 

[Scotty_Tradewind]

How about filling it with ready-mx concrete?

yup reckon that should fix it..... has been used by boat and ship builders in the past to either serve as a ballast or hold heavier ballast in tight.

The top of my Twister keel was finished off in concrete.

S.

 

[Scotty_Tradewind]

the holding tank is completely inaccessible. If we could do any of the above we could probably service, repair it and use as originally intended

well you made that clear in your OP didn't you?

Question: what would you do with the decommissioned one? Leave it empty? Fill it with something stable (we could do with the ballast there)?

S.

 

[ChattingLil]

well you made that clear in your OP didn't you?

Question: what would you do with the decommissioned one? Leave it empty? Fill it with something stable (we could do with the ballast there)?

S.

my apologies for coming across as stroppy - not intended. Thanks for the reply though - all useful under other circumstances - just not for me in this boat!

 

[Hadenough]

Cement slurry with glass fibre rovings.