Rusty cistern - Yup, another issue.

[DIY-JC]

That damn cistern has thrown up another issue.
After taking my cast iron cistern down to re-plumb it I was surprised how "rusty" for better words ,the inside looked. Pretty pitted and in places looks like it was ready to fail. See attached pictures. What can I do to treat and protect it? I would rather not sand-blast because I don't think it would survive the process.
Obviously I want to treat what is there then waterproof it. Any ideas?

 

[Wayners]

Sand.
Treat.
Spray foam inside.
Carve out a bit to smooth off and shape up.

I did that on my ceramic cistern to stop condensation forming. You could do the same to keep iron dry

 

[opps]

I use Owatrol oil as a paint additive to help the paint flow. The same product can be used as a primer to protect rusty iron.

Perhaps email them and ask if it will be suitable for your purpose.

Contact Us | Owatrol Direct

If you have any questions or comments and would like to contact us, we have many ways of doing so - chose from phone, email or fill out our contact sheet.

www.owatroldirect.co.uk

 

[Madrab]

Use a rust treatment to convert the rust, wire brush attachment on a battery gun and clean it all up and then you could use a tanking membrane or similar to paint a waterproof seal onto it. Bitumen paint would also work. The trick is prepping the rust so it doesn't bubble up again and lift whatever waterproofing is added on top

 

[ChrisJP]

Just get rid of the old cistern and replace it with a plastic one. Cleaning off all the old rust and converting what's left will be VERY time consuming and may actually perforate the cistern anyway. Any treatment you then apply to "waterproof" it may not last long and end up flaking off and causing more trouble.
With plastic cisterns so cheap what's not to like about replacement?
In this case it is broke, so it needs fixing!

 

[DIY-JC]

Cheers ChrisJP - Lets just say that plastic is a no-go.

 

[jj4091]

Pardon our interruption...

 

[DIY-JC]

Thank you for the idea jj4091 but would that last constantly under the waterline?
Owatrol looks like a way forward opps. They have recommended Owatrol CIP but I'm just waiting to see what can overcoat it, hopefully some tanking material like Madrab suggested.
Wayners idea of spray foam inside gave me an idea, would a thin fibreglass be able to tank the cistern after rust treating?

 

[Madrab]

would a thin fibreglass be able to tank the cistern after rust treating?

Yes, you could use a fibreglass matt and resin but again the key would be to ensure that the rust couldn't return, if it did then anything on top of it will lift up and loosen. Hence the ideal to seal it properly and paint it.

 

[Nige F]

applying fibreglass mat and resin will do nicely .That has been done on large cisterns.

 

[Madrab]

+1 - they used to line old 150 gal lead storage cisterns in the communal attics in the old tenements with fibreglass.