Aquatic Technology Pool & Spa, "Creating Water as Art."™

Aquatic Technology Pool & Spa, "Creating Water as Art."™
Pools as an art form - the way it should be!

Wednesday, May 23, 2012

Infinity & Vanishing Edge Pools - Preventing Leaky Weir Walls

Infinity and Vanishing Edge Pool Walls - Stopping the drips

I've had a number of requests for the addition of some graphics to help readers visualize the infinity edge weir wall and basin relationships.

The graphics will be hand drawings and not our usual computer drawings.  It is our intent to help you understand the concepts and not to provide a "cut and paste" work product on the Internet.

Where does the waterproofing go?

Since the vanishing edge wall is in effect a freestanding dam, it makes sense to incorporate waterproofing within the cement of the wall.  No matter what remodeling or work occurs in the future, there will always be that non-corruptible layer of protection.

I specify an additional layer of protection on the both surfaces of the wall, as well as inside the entire basin.  Any tile or stonework on the "dry side" of the vanishing edge wall or lining the catch basin, should extend down and into the minimum operating level of water that always remains (MOL).  Because the water level in the basin is constantly changing, the walls above the MOL are subject to constant wetting & drying.   Therefore any plaster based finish will be subject to shrinkage cracking.

The yellow highlighted area illustrates the minimum areas that should receive a topical waterproofing.  I prefer an elastomeric membrane topped with a compatible skimcoat of thinset (products from the same manufacturer).  This will ensure that the plaster will bond on the inside of the pool.  This membrane also prevents any moisture from intruding into the wall, since plaster is not waterproof.  Yes, you read that correctly, plaster is not waterproof.  It is after all, just cement and sand - and water does wick through cement based products.

 The yellow highlights indicate the minimal areas of waterproofing required.

Which way to tilt the weir?

It is a matter of preference.  I prefer to tilt the weir down and into the pool.  It creates the illusion that the pool is slightly larger than it actually is.

It is a fact of physics that water will always seek level.  It is also true that water will migrate via capillary action through cement.  If no waterproofing is employed on the vanishing edge wall, then water (2 large arrows on left) will quickly begin to seep through the mortar bed (green).

No matter which way the weir tilts, since the water level in the pool is higher than the potential exit point on the dry side, hydraulic pressure (weight) and gravity will force the water to pass through the mortar.  Left unchecked, over time the water in the pool would equalize with the exit point on the dry side of the wall (indicated by the blue line & double headed arrows to the right of the weir). 

Purple -  Granite tiles/slab
Green -   Mortar leveling bed
Pink -     Interior plaster/tile finish
Yellow - Dry side VE wall tile
Blue -     Water & migration paths
Blue Line - Equalization level

The water then migrates through the mortar bed, behind the dry side tiles.  As the water discovers cracks in the grout, some exits carrying with it dissolved salts (efflorescence).  The water will continue to flow through this mortar or in hollow areas behind the tiles, until it either encounters a dense area of mortar or a sound area of tile.  The remaining water will exit at this lower elevation, carrying with it a majority of the dissolved salts (hence a greater build up of efflorescence). (see the prior article on efflorescence).

By incorporating waterproof additives into the mortar bed, one can effectively seal the capillaries in the mortar, thereby retarding water migration.  The addition of a membrane a top the mortar bed, only leaves the layer of thinset (under the granite and tiles) as a possible migration path for the water.


The reinforcing shown in the drawings is not intended to represent the actual steel schedules one would utilize.  Instead, they are shown so that you understand how this all goes together.  However, the actual vanishing edge wall should never be less than 12 inches thick with double curtains of steel.  The exact wall thickness, steel size, spacing and placement is determined by the structural engineer.

The catch basin elevations were drawn arbitrarily.  Based upon a projects needs, the catch basin could be above, below or even with the pool floor.  The catch basin could even cantilever in mid-air.

Deepened keyway footings are shown in a drawing, but not every vanishing edge pool requires them.  Some require more elaborate foundations and others no specialized foundation.  The geotechnical engineer will outline this in his soils report for the structural engineer.

Paolo Benedetti - Aquatic Artist
"Creating water as art."™
Aquatic Technology Pool and Spa