Cement Dams and Fish Ponds

The use of BULLDOGSEAL in the waterproofing of cement dams and fish ponds


Mnr. Manie Wilken from the company Vallei Voorsieners in De Doorns, waterproofed a wide variety of Cement farm dams and fish ponds between 2007 and 2010 using BULLDOGSEAL.

We went to speak to Manie and he shared the following with us.

As a Hardware store and stockist of BULLDOGSEAL, Manie received many enquiries for an applicator that could do the sealing of the dams and decided to start offering the service in the region.

“We sealed approximately eight (8) cement farm dams and large fish ponds with BULLDOGSEAL and some of the dams that we know about, that we sealed in 2008, still shows no leakages.”

Manie approached the sealing of each dam as follows.

The first step is to empty the dam. The dam was then inspected for loose material, possible causes of the leakage and obvious cracks. In some cases where structural cracks in the walls occurred, the dam was firstly strengthened by placing two (2) or three (3) 16mm steel cables tightly around the dam in order to strengthen the structure. Thereafter the cracks where repaired and the walls sealed.

“Allow enough time for the project. We usually worked on five (5) days for the cleaning and drying treatment and 3 days after the final coat. Remember, the pond surface must first be completely clean and dry before you can start to repair and seal. ”

Once the dam was clean and dry, the large cracks were cut open, all loose material removed and brushed clean with a steel brush. The first step was then to a make mixture of BULLDOGSEAL and clean River sand to make a paste, which was applied with a scraper in the deep cracks, filling the crack until it was flush with the surface. For the primer coat BULLDOGSEAL was diluted 1:1 with water and painted over the repaired crack surfaces and approximately 50 mm either side of it. Allow to dry well before applying two (2) coats of Undiluted BULLDOGSEAL as top coats. Every coat must be allowed to dry properly.

“Sometimes we just fixed the cracks and in other cases we sealed the whole dam. When a dam exhibited hairline cracks, BULLDOGSEAL was very effective in sealing those cracks. “

The process involves the following:

  1. Empty the pond empty and clean thoroughly.
  2. Inspect the dam for loose cement, cracks and possible leakage.
  3. Fill the cracks with BULLDOGSEAL and Sand mixture. Allow 24 hours drying time.
  4. Apply Primer (BULLDOGSEAL 1:1 diluted with water).
    BULLDOGSEAL should always be applied with a brush. (Block brush or soft broom is also suitable)
  5. Apply two (2) coats of undiluted BULLDOGSEAL.
    First coat: Painting in one direction, with around 2 strokes.
    Second coat: Layer two should then be applied in a crosswise direction, also with the minimum strokes and painted in one direction.
    Allows one (1) day between layers.
  6. Allow three (3) days after the application of the final coat.
  7. For fish ponds: Rinse and wash the pond gently with a sponge and water, drain and repeat until there is no more visible foam. Fill with clean water. Irrigation dams can directly filled and used.


“We sealed many fish ponds and especially Koi dams. According to the manufacturer BULLDOGSEAL is not harmful to the fish, and I never experienced any problems with the fish after the dams were sealed with it. What we did do, was to wash the fish ponds out well with a soft sponge and fill and drain the ponds about three (3) times until there is no more foam was visible.”

A hint from Manie.

“My experience was that structural shortcomings were the cause of the leaking dams in most cases. Especially the outlets and seams between the floor and wall surfaces must be thoroughly checked. It is important to not take any shortcuts and, in the case of obvious structural damage to consult an engineer. “

“I will definitely recommend BULLDOGSEAL for the effective sealing of dams.” Mr. Manie Wilken.

For further information please contact Urban Tribes.
info@urbantribes.co.za | tel. 021 712 0209 | www.bulldogseal.co.za