The history of swimming pool construction can be divided into two distinct eras - Before PVC liners and Post PVC liners. Before PVC liners were invented pools had to be built using heavy reinforced concrete construction. The introduction of PVC liners allowed the development of modular panel pools and concrete block wall pools that are not as rigid, stiff and costly as the concrete tank type pools that had to be designed so that they never cracked at all, just to ensure that they did not leak.
Before PVC liners there were only two methods used by professional pool builders to build swimming pools:-
By construction of a very heavy thick high reinforced concrete tank using formwork and other special concrete techniques
By construction of a quite thin reinforced concrete tank using very high strength "Gunnite" concrete that is sprayed onto timber forms using high pressure compressed air.
Neither of these techniques were particularly suitable for private pools because both types should be designed by a professional engineer who will require the information from a full scale site investigation. Highly skilled site operatives and heavy complex equipment is also required and so this type of pool is also very expensive!
To reduce cost many pools were also built using concrete block walls that were constructed on a concrete base slab that also formed the floor of the pool. Builder used various techniques to try and ensure that such pools did not leak. Some of them held water and most did not - and if they did - not for long!
Many different materials were used to try and waterproof the pool walls (fibreglass, bituminous tanking, chemical membranes etc.) but all of them work for a while until a slight structural movement takes place (often caused by temperature change) that cracks the waterproof lining. The pool then starts to leak. The saturation of the external ground can then cause more structural movement that increases the stress on the waterproofing and causes the pool to leak even more - until it gets so bad that the pool becomes useless.
Fibre-glass pools were also available but they have always been looked on as a second class cousin to concrete pools because the fibre-glass pool industry has never really developed a high performance product that is equivalent to the yacht industry where international standards for fibreglass boats have been imposed by organisations like Lloyds. There is no doubt that very high quality fibreglass pools can work well - but it is very difficult to produce this quality and it requires a large temperature and humidity controlled workshop.
The Big Secret of PVC liner pools is that the structure into which they are put has to be stable enough to be absolutely certain that structural failure will not occur but not totally rigid . The important result is that any cracking caused by small structural movements does not lead to leaks because the water proofing is provided by the PVC liner and not the pool structure itself - this is a massive advantage. This allows the concrete block wall pools to hold water in a way that they have before!
The invention of the PVC liner has been the most significant thing that has ever happened in the global swimming pool industry. PVC liners are now produced that are suitable for every type of pool - from the heaviest used commercial pools - to the pools with the highest environmental loading from ice, snow and the sun.
It could be argued that any pool builder that is not using PVC liners is providing his Clients with a sub-standard product simply because of the leak-proofing and durability of this amazing product.
The only downside of PVC liner technology is that manufacturers of the modular panel pools have jumped onto the pool construction bandwagon and produce an array of panel pool products that are fine for above ground pools - but are entirely unsuitable for buried in-ground pools, for instance, in the very variable ground conditions of south France where they are now frequently used.
PVC liner pools are sadly getting a bad reputation because their use has allowed the cowboys into the pool industry. Remember - blame the cowboy for any problems that you have with your PVC liner pool - not the liner itself.
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