[VAC] Holding Tanks - what plastic in '76?

["Jim Combs" <jimcombs@xxxxxxxxxxxxxxxxxx>]

Title: Holding Tanks - what plastic in '76?

 
Hi all.
My black water tank needs a small repair done to its vent fitting.
This is a 1976 model, and I believe the plastic to be polyethylene
but I'm not 100% sure.  The fittings were all welded in during its
original construction.  I'm attaching a photo.  Can anyone tell for
sure from the photo if they are indeed HDPE - or otherwise? 

Thanks,
Jimbo / '76 Sovereign