I'm building a fairly large raised brick pond in the back garden. It's walled on both the inside and outside of the pond, so you can't see the foil.

the wall stretches out about 7,5 meters (24ft) round, and is about 1 meter (3ft) tall. The wall is cemented, and flushed afterwards with normal mortar (based on portland cement)

  • Does the water eventually break down the interior wall? I know it will inevitably damage it by time, but will the wall hold?
  • Does the water get effected by the mortar in such a way that it won't get 'clean'. (for plant growth purposes only)

The first year, only waterplants will inhabit the pond.

Different sources give different perspectives: some say to clean the dried wall with vinegar, others say that I have to fill the pond with water, adding 1 liter of vinegar with every 100 liter water... others say don't do anything. What to do?

1 Answer 1


Yes, mortar and concrete will affect water quality for the first little while. How long depends on the pH of your local water and how diligent you are at reducing the reactivity of the mortar by using acidic agents like vinegar. If the pH of the water tends to become extremely alkaline you can counteract this with muriatic acid. However there are other considerations.

If you are going to the effort of building an enclosure like this I assume you want it to last more than a few years. Water is actually quite corrosive and will leach calcium from mortar. Your wall might have a reduced lifespan because of this. It is more likely that slight shifts in the base due to the weight of water (10 pounds per gallon) will cause cracks in the mortar.

This is a job for EPDM pool liner!

  • Yes, it adds to the cost.
  • With an expected lifespan of over 25 years and good heat water and weather resistance this is the product to use if you only want to do it once.
  • do not use swimming pool liner which will leach chemicals into the water
  • it can be tricky to fold the liner inside an enclosure so practice before the final lay.
  • see the attached diagram for how to avoid capillary action between folds in the liner which causes hard to detect leaks

Edit: I touched up my quick little drawing to show that the liner prevents water from touching the mortar and brick, hope that helps.

How to use pool liner

  • Ah, thank you! especially about the acid agent... About the EPDM, I already use it! it's perfect stuff, unbreakable! However, where your liner 'leaves' the wall after one brick, mine waits 9. So that means 7 to 8 lines of mortar.
    – Joris
    Commented Jul 24, 2012 at 17:34
  • You will not see anything behind the EPDM pond liner. I have one 20 years old with cinder blocks and soil behind it , no clue what is behind by looking at it. Commented Feb 5 at 20:19

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