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How to replqce rainwater tank decking?

Just Starting Out

How to replqce rainwater tank decking?

Hi everyone,

I have a rainwater tank outside which I am replacing with a 5000litre poly tank.

The current tank sits on a wooden decking which sits on top of 3 brick pillars. I need to replace the wood decking as it is all rotten and wont support a new tank.

I have bought lengths of steel tubing x6 to lay across the 3 brick pillars which will easily hold 5+tonns of water.

On top of the steel tubing I want to lay a wooden decking.

So my question is.......

Is treated pine decking ok to use for this or should I use a hardwood decking?


Bunnings Team Member
Bunnings Team Member

Re: rainwater tank decking

Welcome to the Bunnings Workshop community @chad47. It's brilliant to have you join us, and many thanks for your question about decking selection.

Hardwood decking would be considered superior to treated pine in durability and structural integrity. Hardwoods like Merbau are naturally resistant to rot, decay, and insects, making them more durable and requiring less maintenance over time. They are also stronger and less prone to warping or cracking under heavy use, offering a longer lifespan and better overall performance.


Regarding the overall project, I'd encourage you to enlist the services of a professional to ensure your proposed layout is capable of supporting the required weight.

Please let me know if you have any questions.


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Home Improvement Guru

Re: How to replqce rainwater tank decking?

Afternoon @chad47 

I would definently be going the route of hardwood decking over pine to help out with 5000L tank. Is that the same size as the existing one you have?Structually I havnt used steel beams to replace timber ones so I am not sure how they compare. I would expect them to be stronger just not sure of size verse strength.


I would like to say a warm howdy and welcome you to the Bunnings community pages :smile: I have seen a few questions like yours come through regaing water tanks so it may be worth taking a wander through the pages.



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