How to fix small holes and rust in a rainwater tank?

[giomoes]

Hi,

I have a rainwater tank on the patio of my house. The pump system is working well, but the tank has some small holes that have become rusted. I would appreciate any advice on how to repair them. Is it possible to fix the holes and rusted areas, or is replacement the only option?

 

[EricL]

Hello @giomoes 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your water tank.

Before you make any repairs to your tank, I suggest having a quick look at your docket to see if the tank is still under warranty. If it is, I suggest calling the manufacturer and filing a claim for repair.

However, if the tank is no longer under warranty, I suggest cleaning the tank of rust and removing as much of the rust flakes as possible. Once you've cleaned the surface, I suggest using Selleys 110g Knead It Aqua Epoxy to cover the holes. My best advice is to allow the water to go down in the tank so that there is no pressure on the putty plugs you'll placing on the tanks.

Please make sure to wear disposable gloves while handling the epoxy.  

If you need further assistance, please let us know.

Eric

[AlanM52]

Hi giomoes,

I suspect something on the inside is causing that rust and likely the distinctive rust line is all the way around the tank.

Can you access from the top to check inside and if needed drain the tank below that rust line and hopefully take some photos.

Cheers

[giomoes]

Hi AlanM52,

Thanks for the suggestion. I looked inside the tank from the top and snap the below photos.

The water level is above the holes. Additionally, the holes are located within the circular area, and the issue appears to be there all over the tank. It seems that something has formed or grown on top of the holes from the inside.

[EricL]

Hello @giomoes 

Thank you for the extra photos of your water tank. Let me tag @AlanM52 to make them aware of your update. It appears that there is corrosive damage inside the tank as well. For long term repair, I propose engaging the services of a professional that deals with water tank repairs. The most likely repair option is to empty the tank and coat it with a potable safe sealer that will protect the steel tank and still allow it to hold the water within. 

If you need further assistance, please let us know.

Eric

[AlanM52]

Hi @giomoes,

You did a great job taking the photos and highlighting those areas of interest.

That could simply be corrosion but why at the same height all around?

You really need to drain the tank below the rust line for better inspection but... if you are reluctant at this stage there is another option.

Endoscope inspection camera.

https://www.amazon.com.au/endoscope-camera/s?k=endoscope+camera

Carefully tape to a stick back from the camera over a distance of about 100-150mm in three places to reduce cable stress.

Cheers

[DIYGnome]

Hello @giomoes welcome aboard, just curious if the rain water is used for drinking or irrigation?

It's my understanding that steel tanks require some type of lining (zinc or otherwise) to help prevent corrosion, periodic maintenance is the only method to ensuring this lining continues to do it's job, given I have not seen a tank of this design before is it possible it was a one-off custom tank?

Either way, you'll need to transfer that water to something else to enable access & repair, not quite the same but I had a motorcycle fuel tank leak that was resolved using an epoxy inner coating & rust preventative outer metal treatment, the product below might be of benefit to you after you've repaired/treated that corrosion 👍

https://www.bunnings.com.au/gripset-betta-1l-waterproofing-membrane-bitumen-rubber_p0960165

[giomoes]

Hi @DIYGnome , thank you for your response.

The water tank is used to fill the toilet tank.

I am planning to contact a plumber to handle the job, as I am unsure how to drain the water from the tank myself, since there is no tap, and I also don't know how to apply the protector/coat to the tank.

[DIYGnome]

Draining the tank is easy @giomoes if you are trying to save the water, use the existing pump to transfer the water to another tank (or unused 240L bins), otherwise simply "gravity syphon" out the water to your lawn with a length of garden hose

The coating is water soluble and is applied with a paint brush (preferably one you don't mind losing), being a potable grade sealant the water would remain untained and drinkable or good for your pets if you have any.

Depending on how much the Plumber quotes a seconds Poly Tank might be cheaper in the end, depends on your situation and physicality, Tank World seconds tanks go for around $350 for a 333L tank (as seen below), price varies on delivery location.