I have a sink and want to add an isolating valve for the taps.  See photos.  The 15mm plastic pipes are at least 20 years old or probably 30- 40 years old.   Should I get a

 

(a) plastic isolating valve and not worry about what brand it is.  In other words, different brands are compatible with each other.

 

(b) plastic isolating value of a particular brand (if so, please tell me what brand)

 

(c) copper isolating valve, and if so do I get a pushfit or compression or either.

 

(d) do not touch it.  (the plastic pipes go under the floor). 

 

Grateful for any advice. 

Edited April 22, 20233 yr by Question

I think I can answer my own question. 

 

The cap of the T junction has the distinctive polyplumb brand markings.  So I'll get a polyplumb isolator.

I did away with all the isolating valves when I replumbed our house. 

 

Considering how irregularly they'll be needed the inconvenience of turning off the mains for an hour while I fix a tap really wasn't worth the extra point of failure or cost  in my opinion. 

Just make sure to fit pipe inserts.

Yup. Polyplumb. Some of these exact fittings still available on eBay. 
 

Thanks very much for your comments.  This came up, as I have to change a washer in a tap.   

 

I don't think the plastic piping is polyplumb, as there are no markings on the pipes.  So there is already a mix of different brands, the T junction being polyplumb. The whole thing has been in place and fine for 20 years. The polyplumb T junction was probably added by a plumber who was extending the water for an extension.   So I'll just leave it alone and switch off the water from the main to change the washer, like Iceverge suggested. 

 

KISS wins again!