In article ,
writes
On Friday, 12 August 2016 02:14:04 UTC+1, bob wrote:
replying to Chris Holford, bob wrote:
boiling water removes caustic soda which gone hard, along with a plunger

I'd think after 4 years he'd have solved it by now.
Try this:
http://wiki.diyfaq.org.uk/index.php/Home_owners_hub


NT
Yes, I have solved it!
-it wasn't blocked in the first place, doh!
I'd just moved in and wasn't aware that shower tray had a 'Phlexiflow'
pumped waste. The problem was with the flow switches and/or the control
unit for the waste pump.
--
Chris Holford