On January 1 US producers and their veterinarians will be entering a new era for use of a variety of antimicrobials that have been routinely used in both swine diets and in drinking water. VFD’s (veterinary feed directives) will be required for many of the feed additives and prescriptions will be required for many compounds added to drinking water.

As a consequence of these changes, many producers have been exploring alternatives for both feed and water. In some cases the expectation is that rather than relying on a feed additive which requires a VFD and bulk bin scheduling, etc., producers will switch to prescription based water added products.

With the possibility of more products being added to drinking water, a quick review of the plumbing of water medicators is in order. Keep in mind that the dosing of water added products is generally based on a medicator having a fixed 1:128 dilution ratio which limits how much product we can inject into the drinking water.

A common complaint I’ve often received in barns is that when products are added to the water, drinking water consumption declines. The complaint becomes – they don’t like the medicine! In reality in a large number of sites they may or may not be reacting to the taste of the medicine because in fact water flow to the drinkers is reduced due to the plumbing of the medicator to the drinking lines.

Most swine facilities in the US use 0.75 inch inside diameter schedule 40 PVC for their in-barn drinking lines. At a velocity of 4 ft/sec flow (at 5 ft/sec it is recommended that schedule 50 PVC be used due to the higher pressures associated with faster flows), this means the lines have a capacity of 5.5 gal/min. The most commonly used medicators have a stated capacity of up to 7 gal/min which would suggest the medicator is not the problem when pigs ‘won’t drink the medicine’.

In fact, the most common limit to water flow from medicators is the line connecting the medicator to the drinking water line. It is very common to see medicators connected using 0.5 inch hoses designed for home use with washing machines. Some of these lines are in fact only 0.375 inch diameter.

If we use the 0.75 inch line as our base, here is how connector sizing impacts flow:

0.375 inch – 23%
0.5 inch – 45%
0.675 inch – 69%
0.75 inch – 100%
1.0 inch – 178%
1.25 inch – 275%