Encouragingly, many papers have now been published on water. Farmers are also providing sufficient drinkers, many with adjustable-height fixings (young pigs grow upwards at about 2 cm per week and the tip of the drinker should raise the pigs head 15 degrees from the backline so as to minimise spillage).

And the way we water sows (badly – bite drinkers should be banned!) is receiving attention at last. So things on the water front are looking up.

Water hygiene
But there is one aspect of watering pigs which, because it is out of sight, is also out of mind. This is water quality, which is taken far too much for granted. 'Water hygiene' in other words.

Drinking water contaminated by pathogens spread diseases like salmonellosis, ileitis, PRRS and dysentery. The PRRS virus can survive in the pipes for ten days or more and the enzootic pneumonia virus for a month.

Moreover, biofilms (an upmarket name for 'slime') protects pathogens. One authority even claims 'it provides coliform bacteria with up to a 3000-fold increase in resistance'.

Smeared with slime
Remembering the sobering experience on our own farm 40 years ago when the pigs got collywobbles we couldn't cure – now, when inspecting a client's bowl or leaf drinker, I always run my finger under the leaf. If it comes out smeared with slime, there will probably be a little chap in there called Balantidium coli which can cause digestive upset and mild looseness.

It is easily removed by ensuring the pressure-washing lance gets behind the leaf, which blasts away the slime and the bugs with it.

Some good advice on waterline hygiene:

1. At every all-in/ all-out break disinfect the water lines too. After removing sludge and debris from the header tanks, drain the system. For non-drainable systems – see below.

2. Use a disinfectant which will remove biofilm as well as killing pathogens. For example chlorine – often used because it is cheap – will not remove biofilm to any appreciable extent .There are several sanitants on the market that will – like Virkon 'S' (DuPont).

3. Follow the instructions carefully as they vary between manufacturers.

4. For example, Virkon 'S' used for 'terminal disinfection' as it is called (as distinct from low-level continuous disinfection, which is possible with some products) is used at 1:200 or 0.5%.

5. After disinfection flush the system. Leave for 30 minutes and refill.

6. If you cannot drain the circuit, try to get it re-plumbed so you can. If this is impractical, use the low level, high-dilution technique with the pigs present.

7. But first, check carefully with the manufacturer that his product is safe for pigs in situ. With Virkon 'S' the dilution is 1:1000 (0.1%) during the period thought to be at risk. For longer routine use, check with the manufacturer.

Why do I think terminal disinfection is preferable to low-level, ongoing treatment?

Because I am sure biofilm removal is more likely to be effective if carried out correctly every time the barn is vacated.

Evidence
Also, on many units I am visiting at present this isn’t done, as evidenced by two units I toured in Eastern Europe in 2007 – one where replumbing was in progress and another where the building was being replaced, so I was able to have a good squint down the discarded, recently-drained lines and insert my little finger.

Sticky 'gunge' was evident, especially on the straight runs. Biofilm!