How to Waterproof a Cinder Block Pool Explained

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For homeowners and potential buyers alike, an in ground pool can be a valuable addition to any property. Constructing one using cinder blocks is cost-effective and straightforward, but the crucial step of waterproofing can pose some challenges.

While some opt for a vinyl pool liner as a quick solution for waterproofing, it’s worth noting that pool liners come at a significant cost and have a shorter lifespan compared to traditional waterproofing methods.

Tools You’ll Need:

To undertake this project successfully, you will require the following tools and equipment:

  1. Eye protection
  2. Heavy-duty gloves
  3. Respirator mask
  4. Wire brushes
  5. Cleanup gear (vacuum, brooms, rags)
  6. Mechanical mixer
  7. Putty knife
  8. Hydraulic water-stop cement (waterproof)
  9. Flex Seal (spray, liquid, or paste)
  10. Drylok Extreme
  11. ¾-inch nap roller, Drylok brush, nylon bristle brush, or heavy-duty masonry sprayer
  12. Sandpaper

Step 1: Seal With Hydraulic Water Stop Cement

  1. Hydraulic water-stop cement, such as Quikrete, is a rapid-setting repair material ideal for active pool leaks.
  2. It’s crucial for waterproofing as cinder blocks tend to chip and crack over time.
  3. Ensure the pool is free of dirt, oil, and debris.
  4. Mix the cement according to the manufacturer’s instructions.
  5. Fill cracks or holes, supporting the material vertically to prevent sagging.
  6. Wait for it to set completely and then sand for a smooth finish.

Step 2: Use Flex Seal on Pool Corners and Edges

  1. Flex Seal is a versatile material that starts as a liquid and dries into a rubberized, watertight shield.
  2. It’s essential for sealing corners, edges, and vertical stops in the pool, accommodating structural settling over time.

3. Wear protective gear and apply it evenly from a distance of 8”–12”.

4. Allow each coat 24–48 hours to dry before applying additional coats.

5. Apply several thin coats for optimal curing and leak prevention.

Step 3: Coat the Entire Pool Inside With Drylok Extreme

  1. Drylok Extreme is a specialized waterproofer that seals masonry pores effectively.
  2. Clean the surface and paint the first coat using a brush, roller, or sprayer.
  3. Wait for each coat to dry before applying the next.
  4. Inspect for pinholes or cracks and address them as needed.
  5. Drylok Extreme can be tinted to your desired color and is easy to maintain and clean.

Annual Maintenance

  1. Properly waterproofed pools require minimal maintenance compared to vinyl liners.
  2. Regularly inspect for cracks, peeling paint, or small problems.
  3. Address minor issues promptly by sanding, applying Flex Seal, and repainting with Drylok Extreme.
  4. Refresh Flex Seal on corners and edges every 5–10 years to prevent drying and cracking.
  5. Be vigilant for efflorescence, and treat the root cause before redoing affected areas.

Final Thoughts

Waterproofing your cinder block pool can be a rewarding endeavor, albeit time-consuming. Allow sufficient curing time for each coating, preferably during warm weather, and follow manufacturer’s instructions closely. Always prioritize safety by wearing appropriate personal protective gear to safeguard your health.

Zubair Saleem

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