Not so spooky really - After I used DS4 on my first boiler (around 1992) the dreaded banging came back in about 6-7 years, much like yours now! That was when I got a new boiler - in hindsight I wish I had persevered with it – prior to putting in the new one, they cleaned the system - and yes the boiler stopped banging!! Food for thought? Reading lots of the posts, many of the experts ‘bang on’ about how good the old boilers were compared to the new ones now! In fact I came across one thread that was devoted to fitters/experts grading boilers - good, OK, avoid.
I agree the main cause is likely to be hard water as I am in the SE. When I got the new boiler in 1999 I considered a water softener, and something else similar I seem to remember that you clamped on the pipes I think, but took the easy route - do nothing!
Incidentally, when you say you ‘…checked your old posy’… do you mean by chance, or did you get a message from diynot.com that you had a new message? In looking over the site for advice I got the impression most of the correspondence was around 2004-2006 – not a lot recently. The only response I have had to my post is yours - so if I write again, I will try a new question possibly.
As to the present, when I’m being optimistic I can convince myself it is OK, but …..I have experienced the ‘signs’ of kettling before so…..! It’s just starting, so I have some time before I have to do something. As to the future, your boiler /system was probably about 15 years old when you used DS40. Needless to say like you, with our systems that much older, (mine 13boiler,/system 33) I am very loath/worried about going for DS40 this time round! Also I am loath to take radiators off - I have heard that that can cause problems. I am presently minded to go for X400 with a lot of pre & post flushing. Any comments out there?
Richard