How do you clean fermenters?

[Ducatiboy stu]

It's been posted before, but having suffered exactly the same issue with certain types of beer only, I'd be looking at making sure I'd removed all chlorine and chloramine from the brewing water. I use 1/2 Camden tablet (potassium metabisulpite) for the 30 odd litres I use for mash and sparge.

Slightly OT

4.1.3 Metabisulfite (Campden Tablet) addition is effective for chlorine and chloramine removal.[SIZE=medium] The tablets are either potassium metabisulfite or sodium metabisulfite. [/SIZE]Both are effective in disinfectant removal.[SIZE=medium] [/SIZE]When sodium content in the brewing water is a concern, potassium metabisulfite may be preferred.[SIZE=medium] [/SIZE]Moderate potassium content in brewing water generally has less effect on brewing performance or taste.[SIZE=medium] [/SIZE]Adding these compounds at a rate of about 9 milligrams per liter (~35 milligrams per gallon or ~1 tablet per 20 gallons) or (~1 tablet per 75 liters) will dechlorinate typical municipal water and leave residual concentrations of about 3 ppm potassium or 2 ppm sodium (depending on the chemical used) and 8 ppm sulfate and 3 ppm chloride.[SIZE=medium] [/SIZE]These ion contributions are relatively insignificant and can be ignored in practice. The reaction equations for chlorine and chloramine with metabisulfite are shown below. Note that extra H+ protons are produced by the reactions (acidity) and the water alkalinity will be reduced.
metabisulfite (S2O5-2) + monochloramine (2NH2Cl) + 3H20 --> 2NH4+ + 2Cl- + 2SO4-2 + 2H+
metabisulfite (S2O5-2) + hypochlorite (2OCl-) + H20 --> 2Cl- + 2SO4-2 + 2H+

4.1.4 Ascorbic Acid (Vitamin C) addition is effective for chlorine and chloramine removal. As indicated in the compound's name, this is an acid and it does reduce water pH if unreacted with a chlorine compound. In distilled water, it can produce a pH as low as 3.0. It is sometimes used in municipal water treatment, however it's pH reduction effect and higher cost can make it less desirable than metabisulfite addition. Ascorbic acid is added at a rate of 1.7 milligrams per liter (~6.4 milligrams per gallon) to remove up to 3 milligrams per liter of chloramine. The reaction equation for ascorbic acid and chloramine produces ammonium (NH4), chloride, and dehydroascorbic acid. Since the dosing is very low, the resulting concentrations are not a concern. Be aware that ammonium is a yeast nutrient and is not a problem in brewing water. The reaction is shown below:
ascorbic acid (C6H8O6) + monochloramine (NH2Cl) --> NH4+ + Cl- + C6H6O6
A similar dosage will also remove chlorine (OCl-) from water. The reaction produces water, chloride, and dehydroascorbic acid.
ascorbic acid (C6H8O6) + hypochlorite (OCl-) --> H2O + Cl- + C6H6O6