Barrie, I use as much vinegar as I have and top it up with water. Not scientific, but it works. The stronger the solution, the quicker it will work, but I'll bet you could have guessed that! I leave it for a couple of hours, then check to see how much fur is still inside. If there is, pour the mix back in again and leave for a bit longer. The one essential is to wash out well, VERY well. Several washes of clean water, preferably warm / hot at least. Alan ----- Original Message ----- From: "Barrie Purslow" <bpduo@xxxxxxxxxxxxx> To: "Model Engineering List" <modeleng@xxxxxxxxxxxxx> Sent: Wednesday, February 22, 2006 7:26 PM Subject: [modeleng] Boiler descaling I am thinking my 5" Britannia boiler is in need of some descaling treatment. I am contemplating filling it with vinegar but have not done this before on such a large boiler. Does anyone have any words of advice - concentration of vinegar, duration of treatment, amount of washing out etc.? Thanks in advance, Barrie Purslow WarringtonUK MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 268.0.0/266 - Release Date: 21/02/2006 MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.