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How to Waterproof Your Pond Using Tanking Slurry

Leaking Pond

If your concrete pond starts to leak it is likely that you can remedy it using SkilledBuild's Hydrobloc+ Tanking System.

Although Tanking Slurry is normally associated with damp-proofing basements it is also an excellent way to waterproof your pond.

There is no need to worry about toxicity as our product is completely ‘fish and animal friendly’. It even has a WRAS certificate which means that it can be used in potable situations of drinking water including reservoirs and water tanks. It also resists chemical attacks making it ideal to line farmyard slurry pits etc.

Why is my pond/tank/pool leaking?

cracked leaking pond

Your pond may be leaking as it is no longer watertight; generally this is because it was either initially laid with too lean a mix, laid without a waterproofing compound in the mix or some form of waterproof coating may not have been applied. Settling of ground may have created cracks or there may have been stresses caused by shrinkage of the concrete when the pond was originally formed. These defects all allow the concrete to become permeable over time. Potentially, this can be identified by a fine tracery of hairline cracks or a powdering of the surface.  

How to Prepare the Pond

  1. First drain your pond.

  2. Clean and dry the pond. If the concrete still seems fairly robust and there is some strength and solidity to it, then a successful repair is likely.

  3. Fully clean the surfaces with patio cleaner or ideally jet wash and treat with fungicidal wash.

  4. Tap the surface over the crack, if it sounds slightly hollow, hack away the surface until you get to a hard surface. Also do this in powdery places. If any cracks show themselves as weak areas of concrete revealing a potential canyon, then chase these out to 2 or 3 cm or as deep as they go.

  5. Clean the surface of any debris.

  6. Coat the edges of any large cracks with the waterproofing and bonding compound.

  7. Next, fill in these cracks with either HydroBloc+ SealPlug following the instructions on its product page or with a strong mix of sand and cement (3 parts to 1) with added Ultimate Pro SBR according to the instructions. It should be noted, however, that HydroBloc+ SealPlug is the superior option as it is designed for this purpose and possesses a balanced anti-shrinkage formulation. N.B. This repair mix is only any good if  the surrounding concrete/render/screed is sound and stable.

  8. Once repairs have been completed then the Hydrobloc+ Waterproof Tanking Slurry can be applied. Please note that repaired areas can be coated after 24 hours, but large areas of new poured concrete or screed should be allowed to cure or 3 days before applying the Tanking Slurry.                

Applying the Tanking Slurry

  1. HydroBloc+ Tanking Slurry performs better on thoroughly dampened surfaces, only then is its maximum penetration achieved. Dry surfaces should be saturated with clean water, preferably 24 hours before application of the tanking slurry and then re-wetted just before application. Remove standing water and pools before application.

  2. Once you are ready to apply the tanking slurry mix the powder with the water to form a paste. It is recommended that the powder is added slowly to the water and mixed to a smooth lump free consistency. When mixing it is important not to mix more material than can be applied within 30 minutes at 20°C. The recommended mixing ratio is approximately 5 parts HydroBloc+ Tanking Slurry to one part clean water by volume. N.B. If the mixed material becomes stiff do not re-mix with water, but discard and mix fresh material.

  3. The paste is applied directly to concrete or masonry structures. We strongly recommend that you apply the product using a medium hard short bristle brush, like our Block Brush. Normal problems of damp and water ingress can usually be addressed by the application of 2 coats of HydroBloc+ Tanking Slurry over the whole area. The second coat should be applied at right angles to the first coat to ensure complete coverage is achieved. The second coat may be applied as soon as the first becomes ‘touch dry’. In all cases the second coat must be applied within 24 hours of the first. In hot, dry climates a fine water mist should be sprayed over the surface of the first coat before application of the second. It is important that no less than the minimum tanking slurry per square meter be applied and it is essential that 2 coats are used.

  4. In cases where the pond/pool possesses angular corners (junctions) and these are suspected as a cause of leakage then these  areas must be repaired and enhanced using HydroBloc+ Junction Fillet (Part 3 of the HydroBloc+ Tanking System). When working with this product be sure not to mix more material than can be applied within 30 minutes at 20oC (68oF). Working time will be significantly reduced as temperature increases. Mix with clean water to form a workable plaster like consistency. It is recommended that the powder is added slowly to the water and mixed to a smooth lump free consistency. Please note, once the mixture becomes stiff and unworkable do not remix with water but discard and mix fresh material. HydroBloc+ Junction Fillet is best applied after the first coat of HydroBloc+ Tanking Slurry has been applied. HydroBloc+ Junction Fillet must be applied on a damp surface to maximise its effect and ideally when the Tanking Slurry is still ‘tacky’.

  5. Now apply the second coat of Part 2, which is to be applied at 90o to the first coat.

  6. You will be able to refill your pond after 3 days. If re-stocking the pond with fish etc. we strongly recommend that a settling in period be allowed and a normal water pH test be undertaken.