CP for large domestic water supply tanks

[corrosionman]

Our London appartment block has four large rectangular galvanised tanks on the roof inside the Tank Room.They were put there 40 years ago and the roof built over them. I believe that galvanising has a limited life and soon we will be faced with huge expense to renew them . Would it be practical to extend the life of these tanks by adding a simple CP to each tank. London water is considered to be very hard.
I would be pleased for any comments
CM

 

[cloa]

Shouldn't you do a internal condition assessment first. Are the tanks purely rain water filled or rain water plus domestic water top up (the later is better as the tanks are always full)?

 

[EdStainless]

Have an expert inspect them. You may be better off with a good blasting and coating. Then installing sacrificial anodes as a back up.
If there is much bare steel now then anode consumption could be fairly high and would present an ongoing maintenance issue.

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[cloa]

And that you probably don't want zinc ions in your water supply.

 

[corrosionman]

Cloa and Edstainless Thanks for your input We did an examination and Yes, the top 6 inches of the tank (where the water level varies) is in very poor condition , so it looks like these 40 year old galvanised tanks need replacing.
Thanks
Corrosionman.

 

[EdStainless]

A good blasting and coating may be a lot more economical than replacement.
If the metal is too far gone for that then maybe only replace the upper sections and coat.
There are special water service coating that are used inside of water tanks and towers with very long life.

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