Are there any downsides to putting old pvc guttering back up? Can rubber seals be bought, or is silicone good for the job? I know its being a bit tight, but if there's no reason to spend on new then why pay.
NT
It does get brittle. I don't think you can buy the seals but you might be able to improvise. Sealants don't seem to work reliably even on stop ends in my experience, and if you have any significant lengths you really do need the rubber seals at "couplings", and to set up the necessary axial clearance otherwise you will have trouble with thermal expansion and contraction.
You can get seals for some types from a roofing yard. Wickes used to do them for their own, but I don't recall seeing them recently. Otherwise, buy a coupler (usually cheapest option) and take the seals out of that (or use it directly).
Sealants won't work because of the large expansion/contraction of PVC as the sun goes in and out. The guttering has to be able to slide against the seals. I lubricate them with silicone lubricant during assembly (except in the case of parts which rely on the seal friction to stay on, e.g. end-caps).
I know it needs to slide, I dont see any incompatbility there. I'd apply cling film to one piece to the silicone only sticks to one, and mix some copper powder into it first so it doesnt get eaten by mould in 5 minutes. I'm not convinced its worth doing, but perhaps, and I know folk that will do it if its workable.
NT
It's likely to cause more work than the money you might save. Guttering is cheap as chips.
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