What it is
Total dissolved solids (TDS) is the dry weight left after a filtered sample is evaporated and dried at 180 °C. It covers everything in solution that a filter cannot catch: common salt, sulphates, carbonates, metals in solution, and soluble process chemicals. Conductivity measures the same thing indirectly and much faster, and the two are usually reported together.
Where it comes from
Salt and brine from food processing, curing and water-softener regeneration; acids and alkalis from clean-in-place systems; descalers; and the minerals already in your incoming water. Softener regeneration and brine discharges are the commonest cause of a high TDS consent breach.
Why it matters
Dissolved solids pass straight through a sewage works and end up in the river, where high salt harms freshwater life. Consents often carry a TDS or conductivity limit for this reason. Unlike BOD and solids, there is no cheap treatment for salt, so the water company would rather you did not discharge it.
What can be done about it
Reduce at source: time softener regenerations and consider a more efficient softener, collect strong brines and acid or alkali wastes for separate disposal, and neutralise rather than over-dose. Where the incoming water is itself high in dissolved solids, Pozzani can advise on treating the supply so less goes into the process in the first place.
Information last reviewed 6 October 2026 by Pozzani Pure Water.