Vokera 80SP descale

Stainless steel.

Cost of a new one £50 plus vat from Ezypart (do a google search)

Are you sure thermister is working properly? That's a cheaper part.

If you had a powerflush you would just connect it to the cold supply i to the boiler and the hot water out, and you would powerflush it with a acidic solution which is all these proprietory cleaners are.

If you can get hold of it use 5 parts hot water to 1 part hydroclori acid. Always add acid to water. Fill the heat ex with solution an leave it to do it's work.

Don't burn yourself on the acid and blame me, this is not advice fo numpties. Don't be like the idiot who burned them selves on hot coffe and then blamed McDonalds. Like as if coffee isn't hot! ACID BURN RIGHT! Use it at your own risk.

For £50 I'd just change heat ex but only after I'd changed thermiste or swapped domestic hot water leeds for heating leeds and run hot ta to see if water gets plenty hot. If it does you need a thermister, i it doesn't you need a heat ex

-- Paul Barker

Brick Acid from builder's merchants is HCl........

In message , Andy Hall writes

Phosphoric acid is gentler ... .........................

Better off using a proprietary preparation from Fernox or Kamco