PVC Membrane Liners - Site-installed

[AlanH]

Is there a difference between the PVC membrane used for roofing and the PVC membrane used for site-installed liners in swimming pools? At a superficial level both are 60 mil (1.5mm) thick (other thicknesses available), have a polyester (or fiberglass) scrim/mesh sandwiched into it, and are highly UV and chemical resistant. PVC membrane used for roofing though is about 1/4 to 1/2 the cost of pool membrane. Other than color/print selection (greater for pools) is there a reason for this?

I'm curious to know because I live in Nicaragua and am building a pool and feel that a site-installed liner is the best option for waterproofing it. However, neither of these materials are available domestically and the shipping, brokerage, import duties and taxes can be very high. "Can be high" because the duties on "pool" materials are 50% whereas on "construction" materials only 5%. Also, an architect friend of mine knows of a project using PVC membrane for roofing that has an overage of material that he can pick up for a fraction of what it would cost me to import new material.

Tile and pre-made liners have higher risks and costs (higher purchase cost, higher shipping costs and duties, worthless warranties, high replacement costs) which is why a site-installed liner seems best. I've tried to talk to a few manufacturers and vendors about the difference but they won't say anything unless I can prove that I at least have a legitimate order for their product (and I really don't want to go through the deception and time of faking an order). So I was hoping some of you may have some thoughts on this. Thanks for dropping by the post.

 

[waste]

I honestly don't know However, if you're doing an 'overlap' liner, I think your alternative is a good idea and most probably workable and viable.

As a caution, I'd say to make the liner easily replaceable

If you'd care to talk more about this, I'm here most nights.

 

[AlanH]

Ted - not familiar with the term "overlap liner". If you have a moment could you explain what that is? Thanks.

 

[renosys]

Alan,

After a quarter century of serving the commercial PVC Pool Membrane industry, the question of using a roofing membrane instead of a PVC membrane designed specifically for pools is one we get on occasion. First off you are correct that a PVC membrane is ideal for use in completely waterproofing your pool. And yes roofing membranes are cheaper but for good reason. There are several important differences primarily centered around the inclusion of talcs (which are used as a filler) and only minimal use of antifungal agents in the formulation- both are factors which make the products much less expensive. Talcs will absorb moisture at a rate that will promote plasticizer migration (the major cause of brittleness and failure) and will also tend to allow pool molds to grow into the membrane.
I have tried experiments and found the best roofing membranes fail within 5 years when used in a pool. The cheaper ones will fail even quicker. Since labor costs are the most expensive part of any installation, a redo after such a short period of time will generally prove unacceptable. Commercial membranes also offer texture for slip resistance, an important feature for safety.

If your pool is a modest one in size you may want to contact a reputable manufacturer such as RenoSys or Delifol and request pricing on partial rolls of varying length. Although identical in formulation and durability, these are sometimes available at significantly lower cost. Modern "infinity series" permanent plasticizer 60 mil reinforced commercial membranes should last 20 to 30 years or longer. I hope this helps in making your decision.

Jason

 

[AlanH]

Jason,

Thanks for the explanation-very helpful. The pool is fairly small and the price differences I'm seeing (although "large" between the two product types) are not a deal breaker relative to the cost of the entire project. And I'm in this for the long term.