The line is the herd's bloodstream
Intensive poultry and pig housing delivers everything through the drinking line — water first, but also vaccines, medications and supplements. Birds drink roughly 1.6 to 2 times their feed intake, rising about 6–7% for every degree above 21 °C, so in a heatwave the line must deliver a third more through the same pipe. When performance dips — wet litter, uneven growth, vaccine failures — the water system is a suspect before the feed is.
The quality numbers
The South African livestock guideline's target for pigs and poultry is TDS under 1 000 mg/L, with real trouble from about 3 000 mg/L — but poultry-specific practice worries about individual constituents long before the total: sulphate past roughly 250 mg/L loosens droppings and wets litter; iron above 0.3 mg/L and manganese above 0.05 mg/L taste metallic, stain, and physically clog nipple drinkers; nitrate is a flag worth testing (watch the units — as-nitrogen versus as-nitrate differ by a factor of 4.4). Notably, research birds have tolerated far higher iron and nitrate than the guidelines allow: the working limits exist as much to protect drinkers, dosing equipment and sanitisers as the birds themselves — which is exactly why treatment is judged against the equipment numbers, not the toxicity ones.
Chlorine, pH and the far nipple
Continuous sanitation is a residual measured where it is hardest to hold: at the drinker furthest from the injector. Working practice targets 2–5 mg/L of free chlorine at that far drinker (checked with a DPD kit), with an ORP meter reading above about 650 mV as the cross-check that the chlorine is actually active. Chlorine's effectiveness collapses in alkaline water, so poultry practice pairs it with acidification into the pH 6–7 band — which also suits the birds' preference for slightly acidic water. Both jobs are ordinary dosing-pump duties, and both fail silently without test kits: dose, then measure, every house, every week. They are also two separate duties: the acid and the hypochlorite run from separate stock tanks through separate pumps and separate injection points, with a length of pipe between the two injectors, and neither drum is ever topped up from the other — mixed undiluted, they release chlorine gas. Where a single medicator must carry both, use a compatible combined product as its label directs.
One sequencing detail matters on borehole water: chlorine converts dissolved iron into rust particles. Filter after the chlorine dosing point, not only before it, or the sanitiser you paid for delivers the sediment that jams the nipples.
Stop the sanitiser before a water vaccination. Live vaccines given through the drinking line — Newcastle disease, infectious bronchitis, Gumboro — are destroyed by the very residual you spend the rest of the cycle maintaining. The routine is to shut off the chlorine and acid dosing, flush the residual out of the lines, add the stabiliser the vaccine label calls for (skim-milk powder or a proprietary equivalent, which mops up whatever the flush left behind), give the vaccine, let the birds drink it down, and only then restart dosing. How long before and how soon after is the vaccine manufacturer's instruction and your vet's programme, not a rule of thumb — the products differ. A vaccination that fails because nobody turned the chlorine off looks exactly like a vaccine that did not work.
Between flocks: kill the biofilm, not just the bugs
A warm, dark, nutrient-dosed pipe grows biofilm — a slime layer that shelters bacteria from the daily residual, seeds every vaccine dose with contamination, and traps iron and scale into nipple-blocking grit. The between-flock protocol used across the industry: fill the empty house's lines with a line-cleaning hydrogen peroxide product at the strength its own label states — commonly around 3% in the line, made up from a concentrate to that product's dilution, never poured in neat — let it stand for the label's stated contact time, commonly a full 24 hours, then flush hard until the peroxide is gone, testing the flush water rather than judging it by eye, and recharge with normally sanitised water. Check the product against your drinker, gasket and medicator materials before the first run: concentrated peroxide attacks some elastomers, and it is a strong oxidiser to handle. Where the water is hard or carries manganese, follow with a descaling run — an acid solution reaching below pH 5 in the line — because scale is the scaffolding biofilm rebuilds on. Trials on commercial houses show lines taken from heavy contamination to non-detectable counts by exactly this cycle.
Pigs: the same war, bigger animals
Piggeries fight the identical battle with wider pipes: total bacteria under 100/mL and coliforms under 50/mL are the accepted screening values, iron bacteria build the same reddish slime that blocks lines and nipple waterers, and pH outside 6.5–8.5 corrodes fittings and undermines both chlorination and water-administered medication. Sulphate is the persistent nuisance — scouring shows up in unadapted pigs well before production losses do, and gradual introduction to a new water source prevents most of it.
Rule of thumb
Judge the water by the equipment as much as the animal: iron, manganese and hardness wreck drinkers and sanitisers at levels the stock would tolerate. Hold 2–5 mg/L free chlorine at the far nipple in water acidified to pH 6–7 (the acid from its own pump and injection point), filter after the chlorine point on ironed boreholes, never skip the between-flock peroxide soak, and turn the sanitiser off before any vaccine goes down the line — the next cycle's water quality is decided while the house stands empty.