We used a caustic mixture in our treatment for the boilers on site. We have now changed the system but we are left with residual caustic solution about 30 litres @ 25% proof, and we are looking for safe ways of disposal. The original supplier does not want to know. the general idea is that it can be poured down the drains as it is also classed as a drain cleaner, as noted on the MSDS. Any one got knowledge of this. sbh

Agree with above... From experience - I used to generate similar as waste (but not as much!!!) and also several different spent acids.. .water company at the time (2001ish) were happy for a neutralised solution to be poured to drain - but only because quantities were limited. (we used to ensure it was acidic and the neutralise with bicarb - all solid residues were kept and disposed of as hazardous waste or recycled back to process) It's worth noting that chemicals were all mixed and neutralised by chemists! Mixing chemicals is never a good idea unless you know what you are doing - coke and mentoes is a good example and poster above outlines the hazards of caustic! For your example I would seek advice from a company able to deal with hazardous waste and ensure your solution is safe and complies with all waste law!