# Forum Home Renovation Metalwork & Welding  water tank repair

## ForeverYoung

I have a water tank, round, gal corro steel, with a flat base.
It had been on a flat blockwork foundation so no drainage and has some rust - one hole about 10mm, but lots of surface rust. 
It's a good size for what I want to use it for (tall and narrow, 240cm x 100cm diameter) so want to repair the base? 
What's the best DIY remedy?

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## cyclic

Start wire brushing it and find out how many more holes are there.
If not too bad you can silicone and screw a patch over holes and rust prep and paint the surface rust however,
you may find the rust is bad inside the tank so maybe not worth repairing. 
What roof is feeding into it, colorbond/zincalume/tile ?
If colorbond or zincalume then don't bother with repair bc these roofs are not compatible with gal tanks and eat them out pretty quick

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## ForeverYoung

> Start wire brushing it and find out how many more holes are there.
> If not too bad you can silicone and screw a patch over holes and rust prep and paint the surface rust however,
> you may find the rust is bad inside the tank so maybe not worth repairing.

  Yes, quite right.
I haven't had a chance to check the inside condition as yet.   

> What roof is feeding into it, colorbond/zincalume/tile ?
> If colorbond or zincalume then don't bother with repair bc these roofs are not compatible with gal tanks and eat them out pretty quick

  Are you saying the water is carrying chemicals that affect the gal tank?
It is for my new shed which is colorbond which will feed into a new plastic tank.
The overflow from this will go into this gal tank. 
I have several gal tanks that have been there 10 years (previous owner) that are attached to the zincalume carport roof.
And a couple on the house, same story but older (previous previous owner).
They are all on gravel bases and no sign of corrosion (I have relocated a couple), not sure if they have some type of sprayed liner inside tho, have heard of that being done, will have to look.

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## cyclic

Have a chat to a tank manufacturer and see what they have to say.
I believe you may be correct with tank liners, don't know bc I have not used a gal tank since 1980 and it lasted 16 years being fed from a zincalume roof.
I do remember gal gutters rusting fairly quickly when fed by zincalume/colorbond roof materials.
You might want to give Lysaghts a call and ask their technical dept about what I am saying
Things may have changed in all these years. 
5th line down in the link "avoid using gal gutters with zincalume roofing" BlueScope Steel Australia: Guidelines for using ZINCALUME® steel

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## ForeverYoung

> ... 
> 5th line down in the link "avoid using gal gutters with zincalume roofing" BlueScope Steel Australia: Guidelines for using ZINCALUME® steel

  I always thought that was because there is a physical connection between them? Brackets etc? Maybe not, maybe it is the water connection. 
Checked one of my tanks that is empty and it does have a sort of liner.
The rusted one doesn't.

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## doovalacky

One way to get a few more years out of it is to pour ~50mm to 100mm of concrete over base after taking a grinder with a wire brush to it and rust stop. Done that previously with some old gal water troughs and they are still going 10+ years latter.  
There are paint on rubber sealants that can also be used in conjunction but run a bit expensive.

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## droog

> I always thought that was because there is a physical connection between them? Brackets etc? Maybe not, maybe it is the water connection. 
> Checked one of my tanks that is empty and it does have a sort of liner.
> The rusted one doesn't.

  Does not need to be touching the water flow in between the surface will cause corrosion.
You can get away with Gal draining onto Zincalume but if you have Zincalume draining onto Gal it will not last very long.

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## ForeverYoung

> One way to get a few more years out of it is to pour ~50mm to 100mm of concrete over base after taking a grinder with a wire brush to it and rust stop. Done that previously with some old gal water troughs and they are still going 10+ years latter.

  Being narrow, 1m, and tall 2.4m getting the concrete in uniformly could be tricky  :Wink: 
And the tap is right at the bottom  :Frown: 
(Will be raising it so tap is usable)   

> There are paint on rubber sealants that can also be used in conjunction but run a bit expensive.

  Yes, I have seen that rubbery stuff on tanks, will have to research it. 
Might not be too expensive as I won't need much.   

> Does not need to be touching the water flow in between the surface will cause corrosion.
> You can get away with Gal draining onto Zincalume but if you have Zincalume draining onto Gal it will not last very long.

  So, that is water acting as a conductor between the two metals? As opposed to runoff 'chemicals' being transported in the water?
Sounds like the later from what you said.

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## ForeverYoung

Some superficial research at biggreenshed ... Rust-Oleum 240ml Black LeakSeal Flexible Rubber Coating Sealer - Bunnings Australia *Rust-Oleum 240ml Black LeakSeal Flexible Rubber Coating Sealer*

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## droog

> So, that is water acting as a conductor between the two metals? As opposed to runoff 'chemicals' being transported in the water?
> Sounds like the later from what you said.

  https://www.ambrosebuilding.com.au/i...nic-corrosion/
It’s the electrickery

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## Marc

Galvanic corrosion is not easy to stop. 
One consideration is ... what do you use the water for? Whatever you do to fix your tank, it i sure to add stuff you don't want in your drinking water. Flush the toilet or watering the garden may be OK.
Stopping rust on the outside of the tank is an easy proposition. Strip the rust, paint with cold gal and top coat with epoxy, job done. Inside is a different song. 
Yes there are product to line tanks but they will not adhere to flaky rust, so you are talking cutting a window, strip the inside, paint and bolt a new larger patch on the hole. The size of the hole will depend on the size of your backside to climb inside the tank, or the tools available to you. Wet sandblasting would be my choice but it requires a 15CFM compressor or larger, plus some inexpensive bits and pieces. You can make the patch for the window from the same bit you cut out, plus adding a flange all around from flat bar ... providing you can weld and grind and fit and drill and cut threads ...
You would be better off buying a new plastic tank.
If it is open top and easy access, you may be able to strip and paint inside too.  
An in between solution is to weld shut all holes, strip and paint the outside. Then drill the top ( if it is closed top) or weld a horizontal bracket to one side, and weld a nut around the hole and screw a long sacrificial anode in the nut all the way down, same as it is done for hot water heaters. It should stop corrosion at the expense of the anode ... providing there is good electrical connection between the nut you weld on the tank and the rod. No teflon or sealant of any kind. 
I have sacrificial anodes on my little cruiser's stainless steel shaft, and on the mild steel rudder. The only time I had some corrosion was when the marina applied antifouling on the anodes, insulating them from the salt water.  
https://plumbonline.net.au/sacrificial-anodes/?gclid=Cj0KCQjw4omaBhDqARIsADXULuVYd0ENpZBLN9LVjco  xX9Vanh0usgFdkFWc7uk26VmUaj4DyoRTbj8aAoiZEALw_wcB

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## ForeverYoung

> https://www.ambrosebuilding.com.au/i...nic-corrosion/
> It’s the electrickery

  That's a good read - thanks  :2thumbsup:    

> Galvanic corrosion is not easy to stop. 
> One consideration is ... what do you use the water for? Whatever you do to fix your tank, it i sure to add stuff you don't want in your drinking water. Flush the toilet or watering the garden may be OK.
> Stopping rust on the outside of the tank is an easy proposition. Strip the rust, paint with cold gal and top coat with epoxy, job done. Inside is a different song.
> ...

  Thanks.
Water is just for the garden.
I will have a go at repairing it. 
I will also look more into my other tanks as the carport roof feeds 2 tank which are plumbed to the kitchen (separate tap).

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## phild01

> https://www.ambrosebuilding.com.au/i...nic-corrosion/
> It’s the electrickery

  I didn't follow the picture comment where they referred to galvanised iron roofing affecting zinc roofing. Thought that was the same thing or was the comment in error and zincalume meant rather than zinc!

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## Cole

If you do ever get inside a tank just remember it can be a lethal environment..  Many excellent OSHA/csb vids on YouTube about this.  
(No doubt the OP/everyone realises this but yeah important safety reminder)

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