Descaling animal drinking lines: The basics, best chemistries, and below-par bets

By Scott McKenzie; Jake Anderson

The act of physically and chemically “cleaning” the inside plastic PVC surfaces and likely the layer(s) of slime, gunk, and microbes from animal drinker lines is usually very easy to do and worth the effort between turns/flocks while houses are empty.
chick next to waterer

The reason most growers execute water line smelly “biogunk” removal without animals present is, frankly, to choose the more aggressive chemistry to quickly break down, shake loose, and dislodge the scaly, crusty solids that often coat the inner workings of pipes, nipples, and pressure regulators. The resulting solid crunchy bits that dislodge from these surfaces after several hours to overnight are then flushed out of the system with full pressure and flow out of the lines and the house. This allows the lines to be then either disinfected as a step #2, or simply filled with fresh (hopefully clean) microbe-free water.

This empty-house method is commonly considered the best-practice approach while animals are not present. It allows the grower to choose from a number of chemistries to effectively and truly descale problem drinker water lines. When animals are present, the descaling approach is limited to either mineral (inorganic) acid or (the least effective) organic acid pH adjustment with citric acid, acetic acid/vinegar, or organic acid blends. This is a very, very slow process that most often works only after a more aggressive descaling has been performed when houses are empty. Additionally, organic acids are usually a poor choice for slow, low-concentration continuous water descaling. They can contribute to biofouling and formation of a snotty, solid bloom of microbes that use the organic acid residue (acetate, citrate) as nutrients to grow and plug up water lines.

Simply adding liquid chemical descaling product into the lines at a dilution rate as listed on the product label is fairly straight forward. Most of the time the single liquid product is injected undiluted through the existing 1:128 dilution (0.78% by volume) medicator pump already present in the house. The entire internal volume of the house drinking water is quickly filled and allowed to descale prior to flushing.

Some products are hindered in cost effectiveness because they are either single simple ingredients that require a greater concentration to descale, or they simply are too diluted “in the jug” (contain more water than others). The dilution rates might include injection at 3% or ≈2 oz/ gallon. The descaling product dilution rate should be strongly considered, along with crusty scale or bioscale management performance, when calculating cost per jug (gallon) when comparing true use cost between products.

This less than optimal 1:128 dilution problem is usually limited to simple peroxides, peracetic acid, or other nondescaling water line cleaners that may also carry a safety or regulatory burden that could place limits on shipping, farm transportation, or storage concentrations. Look for economical 1:128 (or lower) descaling use concentration choices versus 3% or similar more diluted products requiring additional cost and/or time-consuming sump pump or proportioner equipment.

“Scale” and why it’s a problem

Poultry drinker line scale is a complex of groundwaterderived hard minerals that form a layering solid crust on the interior piping systems throughout farm water systems. Scale and mineral deposits have a number of potentially serious impacts on both house equipment and bird health:

  • Water starvation due to restricted water flow (interior diameter narrowing)
  • Facilitation of ideal architecture for biofilm formation and growth
  • Deposition on evaporative cooling pads restricting air flow
  • Enhanced clogged and leaking nipple drinkers due to biosludge and/or metal oxide chunks that disrupt O-ring seals

The basic three minerals of concern in water line scale are iron, calcium, and manganese. These minerals require a different approach to water line cleaning other than the use of simple peroxides, bleach, or peracetic acid, and present a particular challenge to water line disinfectants and biofilm removal strategies. The likely presence of hard mineral deposits inside water lines is usually easy to predict and does not require cutting into PVC to verify prior to descaling drinker systems.

How to determine if true descaling should be part of drinker system management

If hard water is found on your farm, have you ever descaled drinker lines? If the answer is “no”, you should then follow with a few more questions to determine if true descaling should be part of the drinker system management program throughout production cycles, during animal out times.

  1. Do I see scale on my evaporative cooling pads? The scale will likely be very hard and very crusty but will not easily crunch when attempting to remove with your fingernail. It can be red, grey, white, tan, or any combination of colors that show physical buildup on cellulose pad material. Scale on evaporative pads may require a different product for descaling than drinker systems, but is a great indirect indicator of scale inside of PVC drinking water systems.
  2. Do I see color changes on water filters when they’re changed, or are they clogging up with dark colors within a few weeks or months? Again, scale tends to be a darker color and often has a smell that is caused by bacteria that use metals for food. Ironreducing bacteria like iron in groundwater; if you see reddish or brown chocolate color on the white filter material, the farm water has the capacity to create iron or manganese scale inside of water lines.
  3. Do I see staining or color changes on soil where water continually drips? Look at outside barn areas where a leaking cool cell pad or water faucet has slowly leaked onto the ground. Is the soil discolored or has it formed a crusty layer over the soil? The inside of the drinker lines and pressure regulators are likely covered with the same mineral material. It requires descaling to clean and “slick” the PVC and plastic membrane material inside of the lines and regulators.
  4. . Does animal performance deteriorate in hot months or in late stages of growth, prior to market age? If interior diameters of water lines are filled with scale, then water volume flow may be reduced at maximum use times. Your farm’s drinker systems may be water starving animals at peak production — especially in hot weather. Some water systems have been known to have interior water diameters almost completely clogged with hard scale. Water pressure tanks that struggle to keep up may also be a sign of scale build-up. Considered in this scenario: It’s like clogged heart arteries that need to have the lipid/cholesterol “plaques” removed to allow for full flow.

If you’ve answered “yes” to any of these questions, then there are likely scale issues on the farm. Follow-up should include taking a water sample to understand groundwater (well water sample) levels of hardness and additionally ppm levels of iron and manganese.

The dual threat: Hard water and microbes

While hard farm ground water tends to create scale in drinking and evaporative cooling water, biology from groundwater microbes can form a more complex problem for drinker lines. These microbes can be pathogens (like coliforms, E. coli, etc.), but can also be non-pathogenic biofouling microbes that form non-health impacting biofilms.

This type of organism contributes to the physical bioscale that 1) reduces water volume and flow to animals, and 2) can create an environment that creates favorable conditions for both avian and food-safety pathogens to hide and grow. Non-pathogenic scaly biofilms can also create organic byproducts that can, in turn, either feed and/or simply utilize nutritional supplements to compound water clogging.

Bioscale can also contain sulfur, nitrogen, or iron-utilizing microbes found in ground water to impact and increase corrosion and, more importantly, impact taste and odor of drinking water. Removal of scale with a true descaler, followed by either water line disinfection or (for pathogens in ground water sources) continuous drinking water sanitation, is likely the best option for the combination of hard water plus most groundwater microbes in water lines and farm water.

Descaling drinker lines: Water chemistry considerations

Best-in class — Multi-ingredient chemical descaling products: Combination chemistries have hands-down become the dominant players in live animal production, with products like glutaraldehyde/quat combinations, peroxyacids (i.e, liquid and dry peracetic acid), “synergized peroxides”, and chlorine dioxide (acid + chlorite) topping the performance and cost economy categories for both farm/transport surfaces and drinking water applications. The unique and interesting synergies gained by combining different chemistries have proven time after time to enable greater product performance at oftentimes lower concentrations or lower cost for live production.

This is also true for hydrogen peroxide when added to pHreducing (acidification) and chelating chemistry, affording both chemical acid descaling and mineral removal from solubilized surface iron, manganese, and calcium. This is coupled with well-known physical “bubbling” oxidation action on organics and microbes.

One example of an acidic chelating peroxide product available to animal health and the agricultural irrigation industries that can be used overnight at a 1:128 dilution rate is the combination chemistry (acid + chelator + oxidizer) descaler, ProMax. When descaling, look for a descaling product that contains economical high concentrations of both hydrogen peroxide and an acid-donating chelator like HEDP (described below) to chemically descale and physically remove any crusty, smelly layers inside of drinker line systems during out-times between animal production cycles.

Editronic acid (HEDP): Editronic acid, also known as HEDP, is a well-known chelating agent used to bind metals present in water and inside of water lines. HEDP also assists in the stabilization of hydrogen peroxide by protecting against metals that break down the peroxide as it flows from the medicator throughout the interior of the drinker lines, regulators, filters, and drinker nipples. The technical approach of using chelation to assist in the removal of iron, manganese, and calcium as solvation of these metal ions occurs at acidic pH. It allows for best penetration of scale architecture within animal drinker systems. Look for HEDP in your water line descaling product as both a pH reducer and chelator.

Mineral acids: Most mineral acid-based products are a good choice for descaling of water lines if a single ingredient or single class product is going to be used. The behavior and concentration of most mineral acid products allow them to achieve true descaling of the water lines. Hydrochloric and sulfuric acid blends are the most commonly used acids in this category with phosphoric acid being the third. As mentioned above, these acidifiers are a single ingredient or single-class type product and are relying solely on a highly acidic pH for the removal of scale.

The long game: Very slow but steady, continuous water descaling and sanitation

What is the best approach to achieving both descaled, “slick” clean water lines on farms that have poor quality water and pathogens present in source water? It is a combination of true descaling coupled with continuous water treatment to include drinking water disinfection at low ppm levels (i.e., chlorine dioxide systems) as part of a complete animal health management approach. This eliminates the need for water line disinfection after descaling and allows for other animal production improvements based on drinking water (i.e., metal antinutrient precipitation, taste, and odor improvement, etc.). However, some hard-water farm growers might not want to:

  1. commit to the time or equipment requirements for a dual-chemical injection system to operate a chlorine dioxide system,
  2. have farm water pH levels that will not buffer acid products, significantly allowing them to descale and control low level pathogen management in the water itself, and/or
  3. have microbial pathogen and/or metals oxidation needs, but also require pH reduction for slow, low-level descaling that will not clog nipples.

A one-stop-shop approach for hard-water farms not having water starvation (i.e., mostly clogged with seriously thick scaled interior diameters) could be the following acid/ oxidation blend. Remember: This is a very slow approach to descaling and might take months or years to see significant improvement, depending on the thickness of the mineral scale. Additionally, the grower should attempt to use animal safe levels of drinking water biocidal ppm, monitor the ppm at the end of the drinker line, and adhere to label instructions. This is a plan “B’, not a plan “A”:

EPA-registered peroxyacids: These products are equilibrium blends of an acid and peroxide, usually a liquid organic acid and liquid hydrogen peroxide, that forms a synergistic combination of the two as a peroxyacid [see Fig. 1].

Fig. 1

chemical formula peroxyacid

Peroxyacids like peracetic acid (PAA) are excellent biocidal oxidizers that maintain the ability to kill pathogens in the presence of organic material. PAA breaks down into harmless byproducts — vinegar, oxygen, and water. PAA is the overwhelming leading chemistry for chill tank and carcass pathogen management sprays and does not require a rinse. Other peroxyacids and peroxyacid blends have gained traction in animal agriculture but have not been approved for drinking water use. Some PAA products like Perasan A and Peraside have drinking water instructions. All PAA products used for continuous biocidal and descaling applications should have an EPA-registered label, and adherence to that label for drinking water uses should be strictly followed.

Descalers to avoid due to poor performance 

Dry acid packs: Anhydrous or dry acids are available for several acids that are widely used in production such as dry vinegar or citric acid. Most of these dry acids are poorly suited to descaling of water lines due to factors such as cost, concentration, and their behavior in water. Dry acids are much better suited for intermittent pH reduction. Citric acid may be the one exception due to its ability to chelate metals.

Organic acid blends: Organic acid blends like that of the dry acid packs are better suited for uses other than descaling or cleaning water lines. Organic acids are best used for their inhibitory properties or nutritional benefits to the animal. Just like the dry acid products, the organic acids cost, concentration, and behavior in the water make them far less suited to descaling than the mineral acid products.

Hydrogen peroxide: Hydrogen peroxide does not, by itself, perform any significant true descaling of internal drinker line surfaces and should not be used as a tool for this application. Hydrogen peroxide and/or other peroxygens are best used as a co-ingredient with true pH-reducing chemistries for water line descaling or EPA-registered continuous water line descaling and sanitation. Some hydrogen peroxide products are physical “biogunk” cleaners relying on very high levels of oxidation action while others are disinfectants, relying on precleaning and/or descaling to prepare the surface for proper disinfection.


When using any of the aforementioned products, please read and adhere to the label and instructions provided on the label for use in poultry.

About the Authors

Scott McKenzie

Ph. D. Toxicology, B.S. Animal Science, B.S. Biomedical Science
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Jake Anderson

Water Treatment
MWI Animal Health
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