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Pets Large & Small

Stray Voltage

Dr. Kimberly Brokaw, DVM
Walkersville Vet Clinic

(3/2018) Cold weather brings its challenges. Standing out in the cold with a pitch fork and trying to chip away at frozen horse poop is no one's idea of fun. Most horses need extra hay in the winter and keeping water troughs from freezing can also be difficult. Add to that the constant changing of the horses' blankets as the temperatures fluctuate between 60EF and 15EF and it's enough to make someone move to Florida.

While changing blankets, feeding, and cleaning up after horses is labor intensive, maintaining non frozen water doesn't have to be. The old fashioned way of smashing ice every morning is not only labor intensive, but can lead to periods of time when the horses go without water and put them at risk for colic. While I have seen claims that putting salt water in a plastic bottle and having it float in a water trough will keep it from freezing in cold temperatures, it doesn't work. While it seems obvious, antifreeze should not be poured into a water trough to keep it from freezing. If the horse drinks antifreeze it can lead to kidney failure and death. While I'm sure there are other methods to keep water troughs from freezing, electrical heaters are very convenient.

The easiest way to maintain an ice-free water trough is to use an electric water trough heater. Most of the farms that I go to have water trough heaters that are plugged into GFI outlets. Occasionally I'll go to farms with extension cords running to the trough heaters. While less than ideal, I understand that it sometimes isn't possible to have an outlet near the water trough. Especially if using an extension cord, or other less than desirable electric, it is important to check the water trough for stray voltage.

In the last cold snap, it wasn't until I was back at a client's farm for the second time in a week that we discovered there was stray voltage in the water causing the horse to not want to drink. The first time I was called to the farm, I diagnosed the horse with a small impaction colic. I tubed her with water and she was back to normal. Then a few days later she coliced again. I went back out to the farm and found that again she was dehydrated with a small impaction colic. We tubed her again and she returned to normal. At that point I figured there was something going on with the water. I asked the owner if she was having trouble keeping the water troughs from freezing. She happily told me that she had purchased new water trough heaters and hadn't had any problems with ice in the trough. The other horses were drinking and hadn't had any problems. However this mare was a thoroughbred and was more sensitive that the other horses and there was something about the water she didn't like.

I had the client check to see if the horse was getting shocked when she tried to drink out of the trough. While the client couldn't feel an electrical shock herself, when she check with with a voltmeter she had 8 volts in the water trough. She added a ground wire running directly into the trough which eliminated the problem and the horse has been drinking and not colicing. When I talked with her a few days later she told me that she had to correct for stray voltage in all of her troughs and not just the one in the colicing mare's field. She had gotten readings ranging from 6-9 in her troughs even though she had thought they were properly plugged in and had never felt a shock when she'd put her hand in the troughs.

Her electrical set up actually looked fine to me. Her heater was plugged into a properly grounded GFI outlet. Since I have a similar setup for my horses, I decided I would check mine for stray voltage too. I had hired an electrician several years ago to install the ground fault circuit interruptor (GFCI) outlet for the plastic waterer so I figured mine would be at 0. My automatic waterer had 2.4 volts in the water. While it hadn't been enough to stop my horses from drinking, I still fixed the problem.

While fixing my trough, I actually read the instructions on the trough heater. The electrician had done everything correctly. Apparently it's not enough to plug the heater into a properly grounded outlet. The instructions say that you should also drive an 8 foot ground rod in near the tank and run a copper wire from the ground rod directly into the water inside the tank.

I visit a lot of farms. While I don't look at everyone's water troughs and de-icers, I do look at them if it is convenient. I have only been to one farm where I noticed that they had ground wire running directly into the trough. They had wrapped copper wire around a horse shoe and put that in the trough and had the wire connected to a ground rod. The set-up was unusual to me which is why I asked them about it. Apparently the farm manager keeps a voltmeter in her pocket and checks all the troughs everyday as part of her daily chores. She said that her grounding method consistently kept her water from carrying current.

While I'll admit that I still don't check my water trough everyday, I have added checking for voltage to my list of once per week chores. The voltmeter or multimeter are actually inexpensive. I ordered one from Amazon for less than $15. It was easy to use in that I just stuck one end in the water and the other end to the ground rod and it displayed a voltage reading. Having read the trough de-icer instructions, I also have properly grounded my waterer by having an extra ground wire run directly into the water. I would encourage everyone who owns and cares for horses to get a voltmeter, read the instructions for their water trough de-icer, and make sure that they are providing their horses with electricity-free water.

Read other articles by Dr. Kim Brokaw