By: Frank Wall

   
   Vinyl lined swimming pools have been 
built over the years using many different 
types of wall systems ranging from steel, 
polymer and fiberglass to aluminum, concrete
block, and poured concrete. As the 
vinyl-lined pool industry matures and 
builders are looking to build pools with
more amenities and features and multi-level
decks-one system seems to be gaining in 
popularity-the poured concrete wall.
   The poured concrete wall vinyl-lined pool
has a long history of success in the 
Northeast and Southeast areas of the United States. These pools were built using
forms manufactured from steel, wood or fiberglass. Because of the initial cost of
the forming system, these pools were limited to straight wall designs and never
really gained the momentum they needed to be a dominant factor in the vinyl-lined
pool market.
   In the mid 1980s, Heldor, a larger distributor of pool products, came out with
a fiberglass form system that featured freeform pool shapes. Only about 150 sets
of these forms were sold during that time, as their high cost was out of the price
range of most vinyl buiders. These fiberglass models had another disadvantage that
made them an unfavorable choice for pool forming systems-they required a lot of 
maintenance to keep them in shape for repeated use. Manufactured pool kits, on the
other hand, offered many freeform shapes and sizes that couldn't be built with the
forming system and builders could afford to buy one kit at a time to finish a 
project
Aluminum Forming System Introduced in 1985
   In 1985, Modern Pools Systems LLC (MPS), a swimming pool product development and
marketing company based in Columbus, Mississippi, introduced the aluminum forming
system to the pool industry. Although several forming systems were sold, the 
limitations of the aluminum straight wall forms only allowed the builder to build a
few straight wall shapes, which discouraged many builders from jumping on the 
bandwagon.
   Changes in how aluminum-forming systems are manufactured have now resolved the
issues that limited the designs of concrete wall vinyl pools. Aluminum forms now
offer a variety of freeform shapes such as the popular 'Mountain Lake', 'Lagoon' ,
'Kidney', and other custom pool shapes. Walk-in steps, benches, sun ledges and spas
can now be poured with the aluminum forming system.
   This system can also be used to pour an all-concrete swimming pool for market
areas where gunite is not available and can be stacked to pour raised walls for 
water features or rasied deck areas around the swimming pool. With the versatility
of aluminum forms, the builder can also pour retaining walls for various structures.
   The MPS aluminum forming system cosists of inside and outside form panels that
are held together with wall ties that are inspected to yield a minimum 3,175 kg 
(7,000lbs) 'pull strength' and are notched for re-bar placement. The forms go 
together with a pin and wedge system that is fast, easy, and reduces setting and 
stripping time and labour cost.
   The forming systems come in a 1.2m (48") height that allows the builder to pour
this increasingly popular wall height, or a 1m (42") wall height by using depth- 
pouring gauges. The system does not require any footing and is set up directly on
the ground. The forms are sprayed very lightly with a form release agent and then
concrete is placed in the forms using good concrete placement practices. 
Consolidation of the concrete can be accomplished with minimal vibration. The forms
can be stripped after a 12-hour cure time and the pool is then finished like any
other wall system.