14 May 2012

Sealing a Concrete Pond

Posted by bcsands

There are few things in life as relaxing as the tinkling sound of circulating water in a fish or frog pond in the garden. Even more satisfying is building your own pond, perfectly shaped to your landscape – and of course to get the most fulfillment out of your efforts, it must be properly sealed.

The subject of sealing can be easily overlooked in the hurry to fill and use a concrete pond, but it is vital or the whole job could become a frustrating waste of time, money and resources – not to mention loss of pond-life.

Sealing a New Concrete Pond

In actual fact the sealing process begins long before the concrete is poured. It all starts shortly after you have shaped your pond. The sealing process is particularly important if you have decided to build the pond above-ground rather than digging it into the ground, or if you are digging in sandy or rocky terrain.

  • When you have dug or shaped your pond outline, cover the area with smooth, fine sand, ensuring that there are no sticks, stones, roots or any other sharp objects poking through.
  • Measure up the area and buy the appropriate heavy-duty pond lining, remembering to factor in the curve of the pond. Don’t skimp on this material by using cheap building plastic, because it could mean the success or failure of your pond in future years.
  • Place the edging rocks or bricks over the lining, ensuring that the whole pond is lined with a single sheet. If you have to overlap the sheets, make sure the overlap is as wide as possible.
  • Order pre-mixed concrete in a small concrete truck  and, working from the centre outwards, keep the thickness as even as possible (About 40-50mm)
  • Allow the concrete to cure properly by wetting it regularly during hot, dry conditions and covering it during rain and under cold conditions.
  • Look for a specialised concrete pond sealant. This should be both safe for pond life and waterproof for many years to come. You don’t want to have to re-seal your pond once filled.
  • Apply as per instructions and allow it to dry thoroughly between coats.


Re-sealing an Existing Pond

If you have inherited a leaking pond, or find your pond leaks after some time, there are ways in which you can remedy the situation. Here is a checklist of steps to take:

  • Unless the leak is right at the bottom, allow the water level drop to the point where the leak is.
  • Ensure all possible pond-life is comfortably re-housed.
  • Empty the remaining water onto nearby garden beds or down a drain.
  • Scrub the entire pond with a hard scrubbing brush and mould cleaner. The surface must be as pristine as possible before any repairs can be carried out.
  • Allow the pond to dry completely – this may involve covering it when there is moisture around.
  • Repair the leak with gap-filling sealant, Polyurethane sealant or a concrete patch depending on the material you are working on, or use pond liner over the leaking surface
  • Re-seal the pond as if new and use an extra coat for good measure.


Your pond should be as good as new, and, apart from natural evaporation, should require very little future attention. Time to sit back, relax and enjoy that tinkling sound once again.

BC Sands has everything you need to create your own pond, including sand, pond lining, pond  pumps, sealant – and even a Mini Mix to deliver pre-mixed concrete.

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One Response to “Sealing a Concrete Pond”

  1. Hi, I found your info on re-sealing an existing pond very down to earth and informative. Can you supply me whatever appropriate materials/products i need to repair a relatively fine crack 2-3mm wide that is approx. 1/2 metre long on the base and side of a fountain pond. The pond is about 5 years old and is 1 & 1/2 metres wide, with some dark discolouration on the inside base. I reside in rural South Eastern Victoria but no-one locally knows how best to repair my crack, Regards Chris.


    Chris Corbett

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