Three techniques to perfect PVC membrane welds

by arslan_ahmed | October 27, 2022 6:00 am

By Matthew Sands

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A growing number of professionals consider weld-in-place membranes a lucrative addition to their business and are taking the time to train their staff on proper installation techniques.

Weld-in-place polyvinyl chloride (PVC) membranes provide a pool finish with unique benefits not provided by other systems (e.g. marbelite, stone-coloured quartz finishes, or thermoplastic coating). One of the main advantages of the membrane pool finish is it does not crack regardless of freeze-thaw conditions, or even earthquakes. The membrane completely seals the structure of the pool and keeps it watertight. This makes it ideal for both renovating existing pools, especially elevated pools, and new installations.

Once a business has a crew of installers who know how to apply these membranes, this service can easily become part of the company’s offerings, whether it is being used to finish off a new concrete or stainless-steel pool wall project. It can also be used to cover cracked, peeling, or leaking gunite pools. A growing number of professionals consider weld-in-place membranes a lucrative addition to their business and are taking the time to train their staff on proper installation. Weld-in-place PVC membranes not only offer clients a unique and attractive finish for their pool, but also allow companies offering this unique skill set to keep their crews busy throughout the winter.

Training crews

Since proper training is the first order of business, some membrane suppliers offer assisted installations to builders and installers. Pool pros do not always realize how easy it is to install this product, and there are extremely low barriers to entry, as a pool business does not need to invest substantial amounts of money for equipment and the material does not need to be stocked. The membranes come in 24.4-m (80-ft) rolls and any left-over material can be used on another job. In fact, some installers prefer to stock the membrane during spring so they do not need to rely on the supplier, which can limit the risk of longer lead times.

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Rolls of PVC membrane and related accessories are simply ordered for each specific job and can be delivered direct to the job site. There is a learning curve, of course, like anything else; however, compared to other types of equipment repairs, the training can be completed much quicker.

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Welding PVC to the walls and floor of a pool is the easiest to learn, while more intricate parts like stairs and corners can be more complicated. As such, these complex areas tend to be the focus of most installation training.

Understanding the installation process

The installation process of a PVC membrane is straightforward. Before lining the pool with material, installers need to repair the surface first, with most requiring at least a day or less for preparation. Once the pool surface is ready, a felt lining is installed along the floor and walls. The lining is adhered and acts like a pad under a rug. It protects the surface from bacterial proliferation and, while not its main purpose, also gives a soft, slightly cushioned feel.

After installing the felt liner, pool builders roll out 1.8-m (6-ft) wide strips of PVC membrane and heat weld them on-site to ensure a smooth fit. Afterwards, they also cut, fit, and weld steps, beach entries, safety ledges, etc.

Welding techniques

When it comes to mastering the installation of PVC membranes, there are essentially three welding techniques used during different parts of the process to obtain the most water-tight and esthetically pleasing pool finish.

All installers will make use of spot and traditional overlap welding. Both techniques are sufficient to obtain a water-tight liner. However, for those seeking a superior and sophisticated look, butt-welding can also be used along the pool floor to make the welds virtually invisible.

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Spot welding

This is a technique where quick, small “pre-welds” are made between the overlapping layers of PVC membrane to help position and adhere it to keep it from moving before performing the complete overlap weld. This allows the installer to fasten and adhere the membrane. These welds should be made at intervals of about 178 to 203 mm (7 to 8 in.) apart down the seam in preparation of the full overlap welding process. The pieces at this point must be perfectly aligned so these “tack welds” (as they are also referred to) can be detached if
the initial positioning of the material is not perfectly aligned.

Overlap welding

The overlap between the membrane layers should be roughly 51-mm (2-in.) wide to turn it into a 51-mm wide seam. As mentioned earlier, installers should start by spot welding between the two membranes. Once the membrane holds in place with the spot welds, installers should begin applying the welding gun down the full length of the seam. To do this, installers simply insert the welding nozzle under the overlap and heat both surfaces sufficiently to fuse them. While the lap is still hot, installers use a silicone roller to apply sufficient pressure to ensure the two membranes press and fuse together. During this process, installers must be consistent when welding along the lap to obtain a continuous weld (a minimum of 38 mm [1.5 in.]), while at the same time ensuring the welding nozzle remains clean throughout the process. Melted PVC membrane and dust can accumulate on the welding tool; therefore, it is important for installers to remove any debris from the nozzle by using a wire brush.

Butt-welding

Traditional overlap welding works well on the walls and steps of the pool. However, for those installers who want to achieve a superior finish on the pool floor, the use of butt-welding is necessary. The PVC membrane is “butt up” against one another rather than overlapping the material during welding. This welding technique is not always necessary by any means. In fact, many installers do not use this type of weld because a traditional overlap weld is sufficient to obtain a watertight installation. Rather, the use of butt-welding helps improve the esthetics of the pool finish. This technique is more time consuming and, therefore, is only recommended for the floor, which is the most visible part of the pool. The use of butt-welding gives the pool floor an impeccable visual finish. When installers use it in conjunction with a recess cut into the geotextile, this method will give the pool floor a flat finish to provide a smoother surface for bathers to walk on.

For the best butt-welding results, installers should begin by adhering the geotextile membrane to the floor. Then, using a weld-backing strip under the two pieces of the PVC membrane that will “butt up” to one another, they should be welded right in the centre of the head welding band without allowing any space between the two rolls of PVC membrane. When this is done properly, there is no need to use liquid PVC on the seam as the heat of the brass roller will seal the joints together.

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By using this technique, the PVC membrane joints are virtually invisible on the pool floor, particularly at night when the water is illuminated. During the day, when the water is moving, the traditional overlap welding is not apparent. Mastering butt-welding on the pool floor is for those installers who want to achieve absolute flatness with nearly invisible joints that cannot be seen during the day or night.

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Benefits of offering weld-in-place membranes

Weld-in-place PVC membrane liners gives professionals a solution that allows them to build and/or renovate the most pools possible, while still being able to control their construction schedule and overcome their workforce issues. Rather than dealing with long lead times for pool kits, fibreglass pools, or custom-made pool liners, membrane materials are readily available for these types of installations.

Weld-in-place reinforced PVC membranes provide the perfect fit for custom pools because they are installed on-site, even when used on the most challenging shapes. They offer builders a huge advantage because they provide an exact custom fit on-site. Further, as these membranes comprise thicker mesh reinforced PVC, builders can offer the benefit of longevity to their customers, as it will last longer than a traditional vinyl liner.

Savvy pool professionals should take the time to learn how to install weld-in-place membranes and incorporate them into their offerings. Many companies who have added PVC membranes to their repertoire are not only able to provide year-round work for their crews and gain greater control of their construction schedules but are also reaping the profits and benefits associated with this product.

Author

Matthew Sands is a sales engineer with RENOLIT. He has more than a decade of successful experience in the construction renovation sector of RENOLIT, having worked for one of the most well-known European flooring brands. Sands has overseen the renovation of several major projects including La Fenice Opera House in Venice, Italy, and LAC Cultural Center in Switzerland. He can be reached via email at matther.sands@renolit.com.

Source URL: https://www.poolspamarketing.com/trade/features/mastering-pvc-membrane-welds/

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