Category Archives: Construction

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.

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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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Cold Comfort

Shovels often go into the ground after Labor Day, that way the new pool is ready for swimmers on Memorial Day. Whether the timetable will be maintained depends on a host of factors, the most variable of which is weather. Except in extreme conditions, pool construction can proceed as long as precautionary measures are taken by the owner, aquatics consultant, and pool contractor.

In the August 2011 issue of Athletic Business, the Cold Comfort article provides basic knowledge of materials and installation techniques for wintertime pool construction.   For example, each of the four most common types of pool finishes has different temperature requirements.

  • Epoxy Paint — The surface to which the paint is applied should have a minimum temperature of 35°F and be at least 5°F above the dew-point temperature, as it will not cure if the temperature is lower.
  • Marcite Plaster — All materials and affected areas should remain above 50°F for 24 hours prior to and 72 hours after placement of the pool plaster. If applied in cold weather, the plaster coat may separate and create a hollow space between the plaster coat and the concrete pool wall. This development usually occurs after a few years and is likely accelerated by freeze/thaw cycles.
  • Quartz Aggregate Plaster — As with marcite plaster, all materials and affected areas should remain above 50°F for 24 hours prior to and 72 hours after placement.
  • Tile — Normal tile installation conditions are considered to be 73°F and 50 percent relative humidity. Typically, colder temperatures and higher humidity will require longer cure times. There are special tile bonding products that can be used in temperatures as low as 40°F; these products come at a premium cost, but they reduce the cure time and limit the time required to protect the installation from submersion and freezing.