Why black water tank after Vactanning?

[Québec]

After searching through previous postings, and having spent the yesterday and today inside our integral water tank de-rusting and Vactanning accompanied by blow heater to keep tank well above the ambient -1C (I know it's not the best time of year to do it...but needs must!) I'm trying to work out why, if Vactan "has been tested and certified as fit for use in potable water systems", is there a need to apply a coat of non-toxic blacking? Could we fill the tank and use the water safely as of now? What are the advantages of blacking after a complete Vactanning.

[Moley]

What are the advantages of blacking after a complete Vactanning.

None that I can think of, our water tank is Vactanned only.

[david and julie]

I used Comastic on top of Vactan and some small areas are peeling - but not rusty.

 

According to the Vactan blurb it treats rust and then acts as a primer, but I'm curious whether your then supposed to rub down this primer to provide a key for any overcoating.

 

Anyone any idea what your supposed to do?

[nb Innisfree]

I used Comastic on top of Vactan and some small areas are peeling - but not rusty.

 

According to the Vactan blurb it treats rust and then acts as a primer, but I'm curious whether your then supposed to rub down this primer to provide a key for any overcoating.

 

Anyone any idea what your supposed to do?

 

Assuming you used Comastic in your water tank, this is coal tar based and isn't suitable, only bitumen blacking is ok for potable water.

[soggy]

What do the manufacturers say?

[david and julie]

Assuming you used Comastic in your water tank, this is coal tar based and isn't suitable, only bitumen blacking is ok for potable water.

Sorry, I should have been clearer - it wasn't the watertank (thats SS) it was on the everyday battle scars.

 

Soggy - Very little, you could call them minimalist.