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!

Saturday, October 25, 2014

Outdoor floor tiles - proper thinset installation and coverage ANSI A108.5

Efflorescence leaching up through floor tiles, hollow clacking sounds and cracking tiles are usually a result of improper installation practices.

ANSI A108.5 (2005) 
Ceramic tile installation practices are published by the American National Standards Institute (ANSI).  This standards also includes quarry pavers (natural stone tiles). 

ANSI A108.5 - 3.3.2 says that on exterior floors, the average uniform contact area with the thinset mortar shall not be less than 95%.  3 tiles will be inspected to determine the average coverage and compliance.

Both the Tile Council of North America (TCNA) and the National Tile Contractors Association (NTCA) have adopted these standards as the minimum acceptable level of performance and workmanship.

Let's face it, humans beings are like electricity and water - they will take the path of least resistance and effort - lazy !

Trowel marks are actually called "gauge marks."  They are used to create a measured thickness of thinset mortar.  Leaving the trowel marks in place will mean only 50% contact at 100% thickness of the gauge marks.
Improperly installed floor tiles show only 50% coverage.  Buttering the edges will hide these marks and give the "appearance" of 100% coverage.  Click on the image to enlarge.

 A 1/2 inch comb trowel will leave 3/8 inch thick layer of thinset, once the grooves are flattened and leveled.  This means that to achieve a total of 1/2 inch of thinset, both the substrate and tile will require 1/2  inch trowel marks that are knocked down and smoothed.

Why do they do this?  

It saves them 50% on their thinset costs.  
They are lazy.  
They don't care.
No one ever taught them how to do it correctly.  They have never been involved in a construction defect case. 
Tile setters must be reminded that tiles installed in exterior floor and shower applications, must achieve 95% contact with the setting material.

This will ensure decades of performance and a lasting tile floor.
Paolo Benedetti - Aquatic Artist "Creating water as art."™ 
Aquatic Technology Pool and Spa © 
You may contact Paolo Benedetti at: or at 408-776-8220

Monday, September 22, 2014

Proper Hydraulic Design - Swimming Pool Drains

Prefabricated Drain Channels and Covers
   A mental hurdle that is confusing to most swimming pool builders, designers, state and local health departments, building inspectors and even many drain manufacturers - is the compatibility of gallons per minute (GPM) through the cover and the feet per second (FPS) through an unblockable drain, suction sump or cover or the connected pipes.

   Drain sumps, channels and covers that comply with the national Virginia Graeme-Baker Safety Act (VGBSA) list a maximum GPM flow rating.  However, it does not mean that the pipe connections below that cover are permitted to flow at that rating.  

Pipes have a different standard

There are maximum line velocity standards that apply to the connected piping.  Simply stated, a 2" pipe can only flow 28 GPM at 1.5 FPS, or 43 GPM at 3 FPS where it connects to a drain sump.
    What the GPM drain cover rating allows are the grouping of different suction systems.  Multiple branch lines from different pump suctions may be grouped together under a cover, until their cumulative GPM flowrate meets the cover's rating.  This allows multiple system inlets to share a drain cover.
    Pre-fabricated drain channels pose another design obstacle.  They are classified under the VGBSA as "unblockable" drains due to their shape and size.  The VGBSA allows these drains to function as a single point suction, meaning that split drains are not required.  They can be ordered with various quantities of connection points for plumbing.
     Most of these channel drains only provide 2" connection ports that are limited (by law) to a mere 1.5 or 3 FPS (depending on the local standard).  That equates to ONLY 28 or 43 GPM per connection!  

Drain Designs  

1.   Single inlet unblockable channel drains are available with 196 GPM ratings.  
When installed in compliance with the FPS standard, it only has a maximum flow rating of 28 or 43 GPM. 
  2.   Dual inlet unblockable channel drains are available with 227 GPM ratings.  
However, when installed in compliance with the FPS standard, it only has a maximum GPM rating of 56 or 86 GPM.  
3.   Triple inlet unblockable channel drains are available with flow ratings of 320 GPM.   
Yet, when installed in compliance with the FPS standard they are limited to 84 or 129 GPM.
Show me the Math

When you are considering the purchase of a swimming pool, require that the hydraulic calculations (head loss and line velocities) and the plumbing schematics (line drawings) be included in the plans.  Require that the builder note in the plans or specifications, the pipe sizes and the maximum allowable line velocities of branch, trunk and return piping.    

This will ease in the verification of the system performance and compliance, by any project inspectors or consultants.  The next hurdle is getting them to actually build it that way!

The design of swimming pool circulation and piping systems are not rocket science.  But, it does require that one be familiar with the basics of hydraulic design, the idiosyncrasies of the codes, what component ratings really mean and the limitations of those components.

Paolo Benedetti - Aquatic Artist "Creating water as art."™ Aquatic Technology Pool and Spa © You may contact Paolo Benedetti at: or at 408-776-8220