Category Archives: Construction

What Gets Built First – Pool or Building?

When constructing an indoor pool, we are often asked what get built first the building or pool? 

In the cold winter belt, if construction starts in the summer or early fall, contractors frequently erect the natatorium shell with its roof, before the pool is dug.  In this scenario, the dirt floor at deck level can serve as a staging area for the construction of the shell and, especially, the roof.  Once the building is enclosed, the pool can be constructed and sheltered from the weather during the winter months.  In the Sunbelt, the opposite is frequently the case. 

When the Goodwill Games was built in Long Island, the pneumatically applied concrete shell was shot against soil as a backform in the summer months.  The building was then constructed over the pool with cranes staged outside of the building, which lifted much of the material and components, including the roof trusses.  By contrast, the 109’ high roof structure at Georgia Tech was lifted by tower cranes staged on the bottom of the pool after the cast-in-place floor footings and walls were placed.  Empty areas of the floor were left for the movement and location of the tower cranes.  The floor slab voids were cast after the cranes were removed from the site. 

In the United States, the preference is to avoid below grade tunnels and full basements as a means of reducing construction costs.  In Europe and Australia, the custom and practice is to excavate to the foundation footprint of the natatorium at one time, build the cast-in-place pool shell and then finish the other spaces for storage, filtration, switch gear, possible chemical feed systems, storage: chemical storage, etc., plus other storage of dry items for the building. 

There are several options to the finished basement or even a perimeter below grade tunnel.  At Notre Dame, as well as some other pools, a below grade room was created along one of the 50M walls of the cast-in-place pool, as well as behind the pool wall at one end of the pool.  The other two walls were sealed off with concrete walls, but with an access man opening at each end of the space, which has a dirt floor and has pool piping running inside this tunnel.  Under this design, access is limited to rare maintenance and repair needs, the space does not require a finished floor, floor drainage, electric lights, or ventilation.  All of these can be provided on a temporary basis similar to sewer workers when entering a sewer for maintenance. 

The acceptance of this concept is often up to the building code officials and project.

All Stories

Clear As Spring Water

The water released through automatic hydrostat valves attached to the well points under the main outlet sumps is as clear as spring water.  Most lay people expect it to be dirty because of its source in the ground.  While this may be true shortly after construction, or during construction, the gravel sub-base and soil functions similar to that of a gravity filter.  I’m sure this information can be corroborated by Andy, Bob and Scot, all of whom have emptied and cleaned pools.

Sometimes pools are stained due to construction dirt in the below grade pipes which can be washed into the pool if the tank is being filled for the first time through the surge tank and subsequently through the main drain lines.  For this reason pools are often filled through the gutters (main drained closed and gutter pipes open) so the water overflows the gutter lip and runs down the walls.   When the pumps start, the dirt in the suction pipes is drawn into the filters. Another advantage to this type of filling is that it can warm the water, flowing down the walls, several degrees inside a warm natatorium and, inversely, cool the walls and floor gradually, thereby reducing the variable between the incoming water and the warm pool shell.  As most of you are aware, cold water on a warm shell can result in thermal shock and the cracking of the pool tank. 

Another misconception by many is that ground water must be at or below the main outlet elevation to avoid foating the pool tank.  Field experience, and the laws of physics, proves that this is not the case due to the ballast weight of the concrete pool shell.  During the early years of my pool management company, I personally emptied several hundred pools. In a number of cases the automatic hydrostats opened and ground water ran into the pool for as long as thirty minutes while the submersible sump pumps were extracting the water out of the outlet basins onto the deck.  The pool at Country Hill (which was located at the top of a hill) had so much ground water one year, due to rains, that water started squirting up to 6 inches high through the expansion joint at the 5’ break when there was still several feet of water in the deep end. The hydrostats were plugged rather than fitted with check valves. There was a case at a swim club in Collinsville which was down in a small gorge with a clubhouse and tennis courts approximately thirty to forty feet above. When one of the pool cleaning crew unthreaded the brass hydrostat plug in the main drain, it shot over the three meter diving board.  For that reason everyone knew to stand aside and not be over a hydrostat when the plug was removed. 

Hopefully this specific background information will be helpful should you have an occasion to discuss the subjects with clients or operators.

ADA Pool Megeddon??

The DOJ has announced a postponement of the ADA compliance date for swimming pools and spas with a new effective date of January 31, 2013.  As first reported on hydrologicblog  “Pool-Megeddon” and “Reasonable Pool Requirements” the ADA mandates were a surprise.   The new date does not seem to change the more stringent interpretations (some may say DOJ rule making) that only fixed and built-in elements would comply with the standard.  So it appears the portable lift is not an option.  For a complete summary of the Revised ADA Regulations Implementing Title II and Title III download the fact sheets.

Where’s The Leak?

Where’s The Leak?

Last week I received a phone call from a client with a 3 year old pool.  They had cleaned the pool for spring and filled it up.  The next morning they come in and found the water down over a foot.  The first areas of suspicion where the underwater lights and the hydrostats.  It is not uncommon for the conduit on the underwater lights to leak over time.  Typically the fix is to seal the cord around the entrance to the conduit.  The hydrostats can leak when they open automatically and then close.  Occasionally a piece of debris can get caught in the seal.   These were tested and eliminated. 

They then emptied the pool and pressure tested all of the lines.  (Air was used to pressure test the lines.  It is our recommendation not to use air.  Pressure testing with water is recommended and safer).  All of the line held.  Without a clear direction on the source of the leak, they let the pool drain until the water level stabilized.  In this case, it was in the main drain basin just below the pipe.  Over the winter a void had opened underneath the pipe in the concrete.  This allowed the water to leak out of the pool.  The fix was relatively easy with a hydraulic cement patch which the pool contract gladly addressed. 

Having a little extra time during spring start up makes the unknown much easier to deal with.  In this example, the leak was a three day issue, but it did not impact the opening. 

Pool Water Tightness Tests

What is the definition of a water tight swimming pool?

Believe it or not, there is not agreement on how a swimming pool should hold water.  The differences centers around being water tight before or after the final finish is applied to the pool shell.  An example would be should the pool be water tight before it is painted, plastered or tiled?  It is this writers opinion that the swimming pool owner is buying a water tight pool shell and a coat of paint or other cosmetic surface should not be considered the source of water tightness.  As a result, all pools should pass a water tightness test before the final finish is applied.

This conversation gets more interesting when the shell is placed using a cast in place method or a shotcrete method.  Some in the industry have taken the position that shotcrete is not waterproof, but water resistant.  It seems silly that someone in the swimming pool industry would make an argument that the pool shell should be water resistant.

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