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Cementitious Water Damping Products Help Prevent Failures

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Grant Smith explaining water dampening - concrete cracks

Let’s talk about tile and why it’s important to install a flexible cementitious water dampening product behind it. Concrete cracks including shotcrete whether dry or wet. Dry is less likely to crack because of the low water to cement ratio but it will at some point crack. Most cracks are due to shrinkage because as concrete cures it expels moisture and changes volume and gets smaller and something has to give. Shrinkage cracks in pools are not an issue.

The American Shotcrete Association addresses shrinkage cracks in pools and the proper way to fix them. There are damp proofing manufacturers that have specific protocols to fix them. When it comes to tile especially glass tile there is a reason why manufacturers require a cementitious flexible membrane.

After waiting the 28 day cure time before applying tile the concrete is still curing and changing volume. In addition to allowing the tile to flex a membrane allows flexibility so if you incur a crack it will not affect the tile. Take for example the pool in the pictures attached to this post. I was called out to look at water dampening this pool because the owner felt the shrinkage cracks in her negative edge wall was a signal the pool was failing and needed extra help.

This was the least of her problems. Besides the abhorrent shotcrete job and hydraulics the tile was popping off on the edge wall right where the shrinkage cracks were due to the tile installer not installing a membrane to allow the tile to flex as the shell was losing volume. Concrete can take decades to fully cure which is even more reason to install products that will make your tile installation counteract the curing process. As the pool sat and cured with the tile installed and shrinkage cracks appeared it popped off the tile and led to a failure of the tile.

It’s important to follow TCNA protocols and those from the manufacturer.

Grant Smith

Grant Smith is a featured Op-Editorialist for Pool Magazine and President of Aqua-Link Pools and Spas in Carlsbad, Calif. A former SWD Master, Watershape University faculty member, mentor and instructor; Smith is widely recognized as an expert and thought leader in the swimming pool industry.

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Swimming Pool Expert Witness

10 Steps To Avoid Irregular Pool Plaster

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Avoid Irregular Pool Plaster Hydration With These Tips

The cause of irregular plaster hydration and streaking can be prevented with a little forward thinking.

1. Prepare the shell for plaster a few days in advance. Do not rely on the plaster crew to seal the shell on plaster day.

2. Chip out and repair every weeper and wet spot. Water flowing in, will be water flowing out.

3. Depressurize the pipes & remove ALL caps on the return lines and light conduits. Allow the water to completely drain out. Dripping water on fresh plaster will cause streaks.

4. Set the return fittings and seal around all of the penetrations with a cement material (non-shrink grout/hydraulic cement). Plaster is not waterproof (per National Plaster Council). Waterstop rings are highly suggested.

5. Using plaster to seal around penetrations can cause a visible halo effect, because of the excess thickness, white plaster patch or hydration variations.

6. Applying a bond coat to the entire shell will ensure the plaster hydrates evenly (yes, even new shells). The density of the concrete pool shell varies throughout, and so does it’s absorption of water. Bond coating will even everything out.

7. Fill the pool, starting from the deepest area first. Filling the spa first, may allow water to flow backwards through the plumbing and exit the pool lines. This will cause streaking on the walls.

8. An old gym sock taped on the end of the hose captures any sediment in the water and prevents the hose fitting from making any marks. This applies to plastic & brass fittings.

9. Do not use a water truck until there is a substantial pool of water in the basin. The cascading water flow can easily erode fresh plaster.

10. A pillowcase taped on the end of a large fill line can be used to capture sediment.

By following these simple steps, you can ensure you’ve done everything to guarantee an even finish appearance.

Swimming Pool Expert Witness

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Swimming Pool Expert Witness

12 Reasons To Use An Electronic Auto-Fill on Swimming Pools

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Autofill Pools with a Jandy Levolor

Electronic auto-fills are slightly more expensive, but they offer important features required by edge vessels. They are far superior to float or bobber auto-fills for a number of reasons.

1. Electronic fills can activate huge fill lines for larger pools and water parks. The 24vac can activate any size irrigation valve. On a typical edge pool, I use a 1” fill line (compared to 1/4” on bobbers). A bypass line can provide for manual filling.

2. A maximum fill timer protects against catastrophic failures & overfilling. In the event there’s a pool leak, the auto-fill will cease. It will reset in 24 hours or when the power is turned off/on.

3. There is an activation delay, so minor waves from bathers or wind surges don’t cause needless filling.

4. There is no annoying hissing from the bather surges or waves.

5. There is not a large well of stagnant water for algae to grow in. By incorporating an overflow, a standpipe can periodically self-flush.

6. The activation delay eliminates frequent water hammer in the plumbing.

7. A 2” stand pipe is easier to hide in a beam. In fact with some ingenuity, you can incorporate an overflow line as well.

8. The fill tolerance is more precise – excellent for smaller or shallow vessels.

9. They are available with a high level sensor to activate edge pumps if bathers forget.

10. They can be placed on a relay and activated on a schedule. This is beneficial if the property is on a well, storage system or has an irrigation booster pump.

11. The fill line can be plumbed into a return line (non-edge vessels).

12. They are applicable to surge tanks of any depth. Bobber auto-fills are restricted by the depth of the well housing or the length of persons arm.

Sensor standpipes should be set 3-6 inches above the floor of the catch basin. The sensor tips should be set at the 12” minimum operating level. The fill line should ALWAYS be in the surge tank/catch basin on edge pools. Placing the fill line low on the end wall eliminates splashing & noise.

I’ve only had one issue in 20 years – a leaf got stuck across the probes and the unit failed to sense a low water condition. Now I place a perforated suction cover on standpipe opening to prevent debris entry.

Swimming Pool Expert Witness

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Grant Smith

Applying Shotcrete The Right Way

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Applying Shotcrete The Right Way - Grant Smith

These are just two of the many examples of the proper way to apply shotcrete. Pouring or shooting the entire floor first or minimally shooting three feet of the floor and the cove.

This allows rebound and trimmings from the wall to fall on a hardened flooor and be scooped out. Keeping your hand from covering the top part of the nozzle allows the paste and aggregate to stay intact.

Covering the nozzle partially separates the past from the aggregate. If you follow at least these two simple rules that are mandated by the ACI and ASA you will be ahead of your competition in ensuring your client has a shell that will last.

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