How to reseal a PVC pipe penetration through a metal roof?

Question

I'm following up on a thread in last year's posting about Bunning's version of the Turbo poly seal + polyester fleece approach for water-tight sealing on a metal roof. The reply was 'Fastfix Wet Shield One Coat Instant Waterproofing'. However, the specification says not to use on new and old PVC. I have a PVC pipe penetration (vent for a toilet) through a colourbond metal roof. At the time of installation heaps of roof&gutter silicone sealant was applied around a rubber seal unit but the silicone sealant is now looking 'worse for wear' with cracking and lifting (see photo). So should I either 1) do not disturb, or 2) use a product that will seal over (cleaned) old silicone sealant (which one?), or 3) carefully remove the old silicone sealant and reapply new roof&gutter sealant or use another more durable, UV-resistant product (again which one?). Any advice is much appreciated.

DYIChris · Answer

Hi Nailbag,

Thanks for your prompt reply. When the time comes I too will follow @JacobZ's advice  but for now, and after reading his reply, I will be in a 'watch and act' mode.

Kind regards,

Chris

DYIChris · Answer

Hi Jacob,

Thanks for the great advice.

The 'rubber boot' was installed by my long-term plumber/gas fitter (now retired). When I've witnessed his work it was very professional so I assume he placed silicone sealant under the boot and obviously more on top. At this stage I will be in 'watch and act' mode.

Kind regards,

Chris

Nailbag · Answer

Hi @DYIChris

I have 2 out of 3 vent pipes through my colourbond roof that are in the same condition, one has been recently repaired exactly as @JacobZ has described. Though not leaking, they too haven't been installed correctly. The one repaired I had help by a plumber mate as we also had to replace a long roof sheet that was installed upside down that it was installed through.

Nailbag