# Existing Roof:TPO or PVC?



## angoved

When inspecting an existing white single-ply roof, how can you tell if it is TPO or PVC? Or niether? 

The roof I am specifcally thinking of that brought up this question is an older HPG roof over foil faced ISO. It is discolored.


----------



## Grumpy

Try to weld some TPO to it. If it sticks, it's TPO, if not it's probably PVC.  I've only needed to know one time for repair purposes when the property owner was unsure, and this is what I did.


----------



## 1985gt

A number of manufactures of PVC and TPO will put "so and so" TPO on details or "so and so" PVC. Look around pipe boots, inside/outside corners most will have some kind of marking. Other wise your stuck doing what grumpy said. 

Here is an interesting read on HPG

http://caselaw.findlaw.com/us-1st-circuit/1421192.html


----------



## RooferJim

HPG is the old Trocal under a newer name. It is PVC and Is no longer in business in the US.


----------

