At first glance, the idea of waterproofing a swimming pool seems like a very strange one, especially to the ordinary pool owner. As it turns out, it’s essential that the floor and walls of your pool are completely impermeable. If they aren’t, the water from the pool could seep into the ground below, which could lower your pool levels at best, and cause a disaster at worst.
If a bit of pool water is seeping into the ground, it might just seem like a mild annoyance, because you would have to keep refilling your pool. That would raise your power and water bills. But if the ground water destabilises the pool, the walls and ground could collapse, causing a sink hole that could damage property and swimmers as well.
It’s difficult to check and repair pool leaks once you have filled them with chlorinated water, so the best option is to apply your waterproofing before you complete the pool. The base of the pool is called a substrate, and it is usually made from concrete. Apply effective waterproof treatment to this substrate and you will avoid future issues with leakage.
Before you begin, make sure the substrate is completely flat, both on the floors and the walls. Check the surface to see if there are any holes or cracks. There might be small holes that are sometimes described as honeycombing. This happens while the concrete is being poured or pumped, because air bubbles might form during the process.
Clean the honeycomb sections then fill them in using a product like Weberep 331 TX, Weberdry 150 BLC, or Patch Additive and TEC Fast-Set Deep Patch. These products are quick-drying fillers. Keep them moist for 15 minutes to make sure the concrete substrate cures effectively, to eliminate further air bubbles.
These same products can be used to fill out cracks and larger holes. If the holes are really big, chisel them first to make them flat, smooth, and even, then apply the quick-drying filler. Once the substrate levels are all even, use a grinder, sandblaster, shot-blaster, scarifier, or pressure wash to clean the substrate. Ensure that all residue has been removed, because if any debris remains, it will prevent the tile from binding with the substrate, and this can cause later leakage.
If the concrete base has no holes or defects, you can clean it by scrubbing with fresh water. Do one last surface wipe using a sponge dipped in water, then let the surface dry completely before taking the next step. Check the edges and joints of the pool. If the walls are round, check the surface of the curves. For corner joints, check that they have 90-degree edges.
If these corners appear to be compromised, scoop out a groove of 2 to 3 cm, clean the groove, cure it with water, and fill it with mortar that has anti-shrink properties. This procedure is called flashing, and it ensures that the corners do not become the source of a new leak. These processes should be carried out two or three days before you waterproof the pool. While you’re filling and flashing, use a water spray to cure the substrate. Be sure to cure at least twice a day.
Now it’s time to apply the waterproof layer. Two examples of waterproof membrane are TEC HydraFlex and Weberdry 110FX. Both can be applied using either a trowel, a roller, or a spray system. First, apply one coat. While the first coat is wet, put a fiber mesh on the corners and joints, then wait for it to dry. It takes about an hour to dry completely. You’ll know it’s dry when it acquires a semi-transparent sheen.
Add a second coat, laying it at a 90-degree angle to the first coat. Wait another hour to let it dry before adding a third coat of your preferred waterproof membrane. Now you need to let the waterproof coatings set, which takes about a week. During that week, cure the surface twice a day.
At the end of the week, flood the surface slowly to test for leaks. To help you confirm the water level, fill a dish or trough with water and put it near the pool. You can then compare the water level in the dish with the water level in the pool to see if there’s any difference.
If you can’t tell by looking, measure the water depth in both areas and confirm it every few days. They should both lose some water to the wind, sunlight, and air circulation, but the rate of loss should be consistent. If the pool is losing water faster, then there’s probably a leak and you’ll have to start again.
Once you’re confident that there are no leaks, lay your tile and grout, clean the surface, dry it with a clean, smooth cloth, then wait 24 hours to let it set, then fill and enjoy your new waterproof pool.