Swimming Pool Designer Structural Engineer

Hiring a Swimming Pool Designer VS a Structural Engineer to design your new swimming pool project?

Creativity

Let's face it, most structural engineers have the creativity of a bag of sand.  While useful for a specific purpose, their usefulness in developing a creative or innovative design is limited.  Engineers are focused on what holds it all together.

Designers usually have a background in the elements of design, such as materials, textures, color, scope and scale.  Their plan will have placed thought behind the seasonal sun and shade patterns, prevailing winds, lines of sight, foot traffic patterns and peering eyes of the neighbors.  An educated designer will bring their decades of experience and education about fountains, pools and architectural history into play.  While the engineer will rely on their computer and sliderule.

Designer

A designer that does not have a background in building pools, may come up with unique ideas, but will have no idea if they are even feasible or able to be built.  You may become excited about an element of the design, only to be told that it cannot be done.

A creative and experienced designer with decades construction experience will be able to develop a project that meets a clients needs, as well as being functional, practical and executable.  When faced with engineering challenges, they will be able to suggest to the structural engineer options for maintaining economical feasibility.

Best of Both Worlds

How do you get the best of both worlds?  Hire an experienced swimming pool designer/builder to consult on the creation of your design.  The completed architectural drawings are then sent to the structural engineer.

The structural engineer is utilized to detail the concrete and steel to hold it all together.

Creativity, functionality and durability meet.

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220. Visit his website at: www.aquatictechnology.com. All Contents © Aquatic Technology Pool & Spa, 2013. All rights reserved.

Spalling Glass Tile Mosaics Expert Witness

Cracking glass tile mosaics investigated by expert witness Paolo Benedetti

Shards of Glass

Imagine walking into the shower or steam bath, onto hundreds of shards of glass... Not the way anyone I know wants to start their day!  Now imagine being greeted by shards of glass on the floor every single morning!

I was asked to investigate a product liability issue of fracturing glass tile in a steam shower.  The contractor was being accused of installing the tiles incorrectly - tiles the homeowner provided.  It turns out the tiles were installed correctly.  The problem was the glass mosaic tiles themselves!

Why?

Glass mosaic tiles at rest will assume a temperature close to that of their environment.  However, when subject to a blast of hot water or steam, the surface temperature is instantaneously increased.  All the while, the middle and back of the tile are still at the room temperature.

The sudden expansion of the surface layer of glass, causes it to explode.  Small divots of glass, like those caused from the impact of a projectile, pop off of the surface... and onto the floor.

Name Brand Designer

These tiles, while from a name brand designer who licenses her name for use on various products, are actually made in China.  And surely from dubious quality raw materials and under loose quality control standards.

Prevention

How do you prevent from becoming the victim of such inferior glass tile mosaics?  First, think thin.  The thinner a tile is, the faster it can respond to changes in temperature.  The chances of such fracturing is diminished significantly.

Inquire if the tiles are rated for thermal shock to the extremes they may be subject to in a steam bath or shower (especially if you have a "instant hot" shower).

Or, obtain a sample and perform some rudimentary testing of your own at home.  Heat them in an oven to the temperature of the steam bath and then submerge them into 75-80ºF water.  Or chill them and then drop them into boiling water.  Be sure to to protect yourself with the appropriate safety gear.  If they crack... maybe you should delve deeper into their suitability.


Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220. 
Visit his website at: www.aquatictechnology.com. 
All Contents © Aquatic Technology Pool & Spa, 2013. 
All rights reserved.

Clouding and discoloration behind glass tile mosaics

With glass tile mosaics increasing in popularity, so have the complaints about dark spots, discoloration, clouding and color rendition.
 
Installation Practices

Proper installation practices for glass tile mosaics are time consuming and expensive.  The cost for labor and setting materials in a pool or fountain can run from $35-100 per square foot - not including the cost of the tile!

In an effort to bring the installation costs of glass tile in a swimming pool within reach of those with limited means, many installers take shortcuts.  These shortcuts include direct setting tiles, bonding them to incompatible substrates, using inferior setting materials or rushing the installation.

Published Standards

In 2005, in response to many consumer complaints and installation failures, the tile industry created minimum standards for glass tile installations.  This committee was comprised of glass tile manufacturers, manufacturers of setting materials and tile installation contractors.  The results were the 2005 ANSI Standards A108.14 - A108.16 - Practices for the Installation of Glass Tile Mosaics.

These standards were promptly adopted by the Ceramic Tile Institute of America (CTIOA) and the Tile Council of North America (TCNA).

In fact, CTIOA has since promoted the ANSI standards as the ONLY acceptable methods of installing glass tiles.  http://www.ctioa.org/pdf/2008-8-12_Glass_Tile_Report.pdf

Some third world and foreign tile manufacturers publish installation instructions that conflict with these standards.  Installation contractors need to be aware that failing to follow accepted and published industry standards will make them liable in the event of any installation failures.

The bottom line is that the installer needs to follow the most stringent standards that apply to their installation.  YES, that is even if a manufacturer allows for a faster, cheaper and easier method.

Trapped Moisture and Voids 

Moisture, voids or blemishes behind translucent (see through) glass tile mosaics will show through the tiles as a discoloration.  The discoloration can be spot behind a single tile, a random assortment of tiles or an entire installation.  They are unpredictable, occur randomly and may only affect a small portion of a project.

Voids, trapped moisture and blemishes occur behind the tiles from the following installation errors and mistakes:

• the bondcoat skins over before the tiles are set (poor bond, loose tiles & voids)
• using the improper direct bond (two step) installation method
• notches left in bondcoat
• too thin of a bondcoat
• utilizing dark colored grouts - which are visible through the sides of translucent tiles
• insufficient embediment into bondcoat
• too much water in the bondcoat 
• ground water weeping into the shotcrete from the soil
• grouting too soon after setting (the back buttering with grout method may in fact trap moisture)
• insufficient curing of the mortarbed (leveling bed)
• a bondcoat that experiences shrinkage (and results in voids)
• utilizing grey cements -which darkens when wet and will be visible through the sides of the tiles if allowed to ooze up between them
• failing to install a waterproof membrane
• filling the pool too soon
• failing to shade the tiles from the sun prior to filling the pool
• failing to protect the pool from rain (or snow or irrigation water prior) to filling the pool

I am not going to discuss each of the above conditions and why they cause discoloration behind the tiles.  Individually or in combination they can lead to visible setting flaws.

Testing

There are tests that expert witnesses utilize when investigating complaints of discoloration behind translucent glass tile mosaics. These tests analyze the visible color variations, composition of the setting materials, sheer strengths (pull off resistance) and moisture contents.

Samples removed for testing must remain in the same condition as when they were installed.  If they were under water, they must remain wet.  Allowing the samples to dry out will change the characteristics of the sample, rendering their evaluation useless in determining the cause.

Learning Process

The final result of any project evaluation, should be the education of the party responsible for the installation.  Incorrect installation procedures, improper setting materials or a combination of them, are responsible for most complaints of discoloration.  

Installers have been known to blame minerals in the water, airborne mold spores and poor pool water chemistry for causing these discolorations... anything but owning up to their misgivings.

Through strict adherence to the published installation standards and practices, you can be guaranteed a flawless glass tile mosaic swimming pool.

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: 
info@aquatictechnology.com or 408-776-8220. 
Visit his website at: www.aquatictechnology.com. 
All Contents © Aquatic Technology Pool & Spa, 2013. 
All rights reserved.

Glass Tile Mosaics Using Direct Set Method

The Direct Set Method of installing glass tile mosaics IS NOT an approved method.

What is the Direct Set Method?

The Direct Set Method (aka: two step method) is an economical and rapid installation method, reserved for ceramic or stone tiles.  After installation and curing of a mortar leveling bed, a layer of mortar is applied to either the mortar bed or the back of the tiles.  The tiles are then pressed onto the cured leveling bed.

Standards Prevail

Many foreign manufacturers of glass tile mosaics provide instructions that follow third world standards.  Simply stated, they do not comply with the science and standards that apply in modern countries.

Following simple instructions to mix white cement and sand to create the setting bed, will not ensure material that is compliant with the ANSI  performance standards.  The sheer strength, permeability and compressive strengths of this material will be totally unknown.  

More critically, glass tile is susceptable to cracking when setting materials experience shrinkage.  Shrinkage is unpredictable with field mixed materials.  Shrinkage places glass tiles under compression.  This stress is relieved by a glass tile as a crack.

ANSI Standards A108.14, A108.15, A018.16

In 2005, the American National Standards Institute (ANSI) developed specific standards for the installation of glass tile mosaics.  These standards are very precise.  None of these standards allow for the use of the Direct Set Method when setting glass tile mosaics.

These ANSI standards were developed in conjunction with the Ceramic Tile Institute of America (CTIOA) and the Tile Council of North America (TCNA).  Both CTIOA and TCNA promote the ANSI standards as the ONLY APPROVED METHODS OF INSTALLING GLASS TILE MOSAICS.

While the Direct Set Method of installing glass tile mosaics may be cheap, fast and easy - it is not permitted in North America.

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: 
info@aquatictechnology.com or 408-776-8220. 
Visit his website at: www.aquatictechnology.com. 
All Contents © Aquatic Technology Pool & Spa, 2013. 
All rights reserved.

Swimming Pool Bonding Grid

Gounding and Bonding ARE NOT the same thing!

I frequently hear the incorrect statement that "grounding and bonding are the same thing."  Though closely related and even interconnected, they are not the same thing.

Purpose of Bonding

Bonding is installed to ensure that every metallic component of a swimming pool has the same electrical impedance - that is, the same resistance to electricity.  The impedance of a bonding grid should be ZERO.

Redundancy

Redundancy exists in many components attached to a bonding grid, to ensure that the impedance is exactly the same for all attached components.

A case study:
A large pool contained numerous light fixtures housed in PVC niches and connected to PVC conduit.  

Every niche had a bonding wire connecting it's exterior bonding lug to the reinforcing steel in the shotcrete.  

None of the niches had the required interior bonding wire installed.

The impedance reading of all of the niches varied between 250 and 500 ohms, except for one.  That one niche had 0 ohms of resistance.  Why?

The bonding wire from the equipment pad was connected to the clamp on the reinforcing steel, then continued down to the bonding lug on the back of that one niche.  Yes, it also happened to be the niche closest to the equipment pad.

Though all of the other niches were connected to the bonding grid, the concrete and steel created resistance between those niches and the one niche with the "home-run" bonding wire.

The purpose of the internal insulated green #8 bonding wire, is to provide another path to ensure that the impedance is and remains at -ZERO- .

Fatal Path to Ground

All of the grounding wires at a property are interconnected.  At the service entrance (electrical meter), there is a grounding rod.  It's purpose, is to discharge any stray voltage. 

However, the grounding rod may not always present the best source of ground for electricity.  The hundreds of yards of wet steel and concrete in the backyard may actually be a better ground.... so electricity takes the path of least resistance & discharges itself into the earth through the shell of the swimming pool.  Though the water may in fact be energized, a proper bonding grid keeps it all safe.

Now, along comes a swimmer.  They touch a metallic part of the swimming that is properly bonded back to the pool steel & bonding grid.  Though the swimmer is a part of the "loop" they do not feel anything - because the electricity is not discharged into the earth (it loops back).

Now, the swimmer touches a metallic component that is not properly bonded or has a high impedance.  The swimmer is now in the direct path of the electricity as it discharges into the earth through the metallic component.  The swimmer is shocked - maybe even fatally.  Why?  They are in the path to ground for the electricity.

When there is a loop and the impedance is zero, humans are not affected.  But, when the human being is a part of the circuit as the electricity is discharged into the earth - they are shocked.

Simply stated:  The purpose of a bonding grid is to ensure that all of the components have the same potential (impedance) to ground.

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220. 
 Visit his website at: www.aquatictechnology.com. 
All Contents © Aquatic Technology Pool & Spa, 2013. 
All rights reserved.

ACI 318-11 thicker stronger shotcrete pools

ACI 318-11 requires that the shotcrete walls on salt water pool be increased in strength and thickness.  Shotcrete is defined as either the wet or dry process of pneumatically placing concrete.

ACI - The American Concrete Institute

ACI is the definitive expert on concrete.  So much so, that they publish a myriad of standards that relate to concrete and it's use.

ACI Standard 318-11, "Building Code Requirements for Structural Concrete" has been directly incorporated into the International Building Code (adopted by 48 States, except Minnesota) and by the California Building Code.  This effectively makes it the law of the land. 

ACI 318-11 changes the requirements

ACI 318-11 redefined the parameters of the required coverage of concrete required over the reinforcing steel.  Prior versions of ACI 318 were ambiguous as to what was actually defined as sulfate or corrosive conditions.

ACI 318-11 establishes the additional shotcrete protection required when exposed to defined levels of sulfates, water containing chlorides (salts) and permeability.

ACI 318-11, Table 4.2.1 indicates that shotcrete swimming pools are required to meet the criteria for Permeability - P1 (condition defined as: "in contact with water where low permeability is required") AND Corrosion Resistance - C2 ( a condition defined as: "concrete exposed to moisture and an external source of chlorides from
deicing chemicals, salt, brackish water, seawater, or spray from these sources").

The resulting P1 and C2 classifications require specific mix design ratios (ACI 318-11, Table 4.3.1).

ACI 318-11, Table 4.3.1, P1 classification sets a maximum water to cement ratio (w/cm2) of 0.50 and a MINIMUM 28 day compressive strength (f'c) of 4,000 PSI.  While the C2 classification establishes a maximum water to cement ratio (w/cm2) of 0.40 and a MINIMUM 28 day compressive strength (f'c) of 5,000 PSI.

Therefore, any swimming pool that is going to be treated with sodium compounds is REQUIRED to have a maximum water to cement ratio (w/cm2) of 0.40 and a designed compressive strength (f'c) of 5,000 PSI.  Sodium compounds utilized in swimming pool sanitization include sodium chloride (chlorine), sodium bromide (bromine) or sodium (salt-electrolysis chlorination).

The C2 classification (Table 4.3.1) further specifies that the requirements of ACI 318-11, 7.7.6 "Corrosive Environments" be met.  Section 7.7.6 states that the coverage over reinforcing steel shall not be less than 2 inches for walls and slabs subject to such corrosive environments.

Structural Engineers & Building Departments

Many structural engineers and building departments do not abide by the requirements of ACI 318-11.  They either attempt to justify design criteria less than the standards, are not versed on the most up to date requirements or simply fail to comply with the codes.

When there is an issue of structural integrity on your pool, the most recently adopted version of the IBC, CBC or ACI standards will apply in court, whether or not they were enforced by the engineer or building inspector.

Do you want to be left hanging with a structural engineer who will have to defend his decision to design a structure that was below the requirements of the building codes?  
Do you want to take the risk that he will be able to convince a jury of lay people that a weaker structure is acceptable?

I thought not!

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220. 
Visit his website at: www.aquatictechnology.com. 
All Contents © Aquatic Technology Pool & Spa, 2013. 
All rights reserved.

Safe Skimmer Equalizer Lines

Skimmer equalizers should be required when skimmers are the sole source of suction for a pump.

We have proven that main drains are not required for proper circulation.  It is irresponsible to suggest the elimination of equalizer suction outlets as well, and thereby the protection for multi-thousand dollar pumps and proper water sanitization.

Low Flow Conditions

Low flow situations can occur from low water levels, weirs that become askew from kids playing with them, excessive waves, debris (goggles) and wear.  The baskets can become blocked due to latex bathing caps, inflatable toys, paper napkins, leaves or other unexpected debris.

When skimmers are the sole source of suction for a pump, the lack of equalizer suction outlets will deadhead the pump or cause a run dry condition, if the skimmers become clogged or inoperative.  The expense of repairing damage to pumps from "run dry" conditions, will become the burden of the designer or installer, because the damage is easily preventable through the use of equalizer suction outlets.

Skimmers

Most skimmers have flow ratings of only 75 gpm.  Skimmers should always be installed in a minimum of pairs, even more if the designed flow rate of the system demands it.   

Equalizers should be installed in a configuration that limits their line velocities to no more than 3 FPS and provides suction entrapment protection in compliance with VGBSA (some jurisdictions have a restriction of only 1.5 FPS).  Since anti-entrapment covers are derated when wall mounted, more than two equalizer inlets may be required to maintain a compliant flowrate.  Equalizers suction outlets should be installed with a minimum of three feet of separation and with the proper sump configuration.

 

Don't merely rely on Variable Speed Pumps

Variable speed pumps have an inherent design flaw.  When they shut down in a “self protection mode” due to loss of prime or low flow conditions, they do not provide an alert to their attached control systems or a remote control panel.   

Critical filtration and sanitization systems may become locked out for extended periods of time without any indications or warning signals.   In commercial pools or spas, this could quickly result in unsanitary and unsafe water conditions.  When system flow is critical to prevent facility damage (e.g. operation during freeze conditions), inoperative pumps are unacceptable as more severe damage to the facility may occur.

The Solution is Inexpensive

 

Properly installed with float valves and equalizer line check valves, equalizers will be dormant most of the time.  Only an equalizer check valve (pop-it check valve) in the skimmer can prevent suction on the equalizer line.  A float valve by itself will actually divert some suction to the equalizer lines.  

Therefore, float valves AND equalizer check valves should be utilized together, to prevent suction on the equalizer lines, except in critical skimmer low flow situations.

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220. 
Visit his website at: www.aquatictechnology.com. 
All Contents © Aquatic Technology Pool & Spa, 2013. All rights reserved.