How far does electricity travel in water?

Water is generally considered to be a good conductor of electricity because if there is a current inside the water and someone touches it, they can be electrocuted.

There are two things to note that may matter. One of them is the type of water or the amount of salts and other minerals, and the second is the distance from the point of electrical contact. This article explains both but focuses on the second to explore how far electricity travels in water.

We can distinguish four zones around a point source of electricity in water (high danger, danger, moderate risk, safe). However, the exact distance from a point source is difficult to determine. They depend on several factors, including stress/intensity, distribution, depth, salinity, temperature, topography, and the path of least resistance.

The values ​​of the safety distance in water depend on the ratio of the fault current to the maximum safe body current (10 mA for AC, 40 mA for DC):

• If the AC fault current is 40A, the safety distance in sea water will be 0.18m.
• If the power line is down (on dry ground), you must stay at least 33 feet (10 meters) away, which is about the length of a bus. In water, this distance would be much greater.
• If the toaster falls into water, you must be within 360 feet (110 meters) of the power source.

I'll go into more detail below.

Why is it important to know

It is important to know how far electricity can travel in water because when there is electricity or current underwater, anyone in or in contact with the water is at risk of electric shock.

It would be helpful to know what is the safest distance to avoid this risk. When this risk may be present in a flood situation, it is very important to have this knowledge.

Another reason to know how far an electric current can travel in water is electric fishing, where electricity is deliberately passed through the water to catch fish.

Water type

Pure water is a good insulator. If there were no salt or other mineral content, the risk of electric shock would be minimal because electricity could not travel far inside clear water. In practice, however, even water that appears clear is likely to contain some ionic compounds. It is these ions that can conduct electricity.

Getting clean water that would not let electricity through is not easy. Even distilled water condensed from steam and deionized water prepared in scientific laboratories can contain some ions. This is because water is an excellent solvent for various minerals, chemicals, and other substances.

The water for which you are considering how far the electricity goes will most likely not be clean. Ordinary tap water, river water, sea water, etc. will not be clean. Unlike hypothetical or hard-to-find clean water, salt water is a much better conductor of electricity due to its salt (NaCl) content. This allows the ions to flow, much like electrons flow when conducting electricity.

Distance from point of contact

As you would expect, the closer you are to the point of contact in the water with a source of electric current, the more dangerous it will be, and the farther away, the less current will be. The current may be low enough not to be so dangerous at a certain distance.

The distance from the point of contact is an important factor. In other words, we need to know how far the electricity travels in the water before the current gets weak enough to be safe. This can be as important as knowing how far electricity travels in the water as a whole until the current or voltage is negligible, close to or equal to zero.

We can distinguish the following zones around the starting point, from the nearest to the farthest zone:

• High danger zone – Contact with water inside this area can be lethal.
• Dangerous area – Contact with water inside this area can cause serious harm.
• Moderate Risk Zone – Inside this zone, there is a feeling that there is a current in the water, but the risks are moderate or low.
• Safe Zone - Inside this zone, you are far enough away from the power source that the electricity could be dangerous.

Although we have identified these zones, determining the exact distance between them is not easy. There are several factors involved here, so we can only estimate them.

Be careful! When you know where the source of electricity is in the water, you should try to stay as far away from it as possible and, if you can, turn off the electricity supply.

Risk and safety distance assessment

We can assess risk and safety distance based on the following nine key factors:

• Tension or intensity – The higher the voltage (or lightning intensity), the higher the risk of electric shock.
• Distribute – Electricity dissipates or propagates in all directions in water, mainly at and near the surface.
• depth “Electricity doesn’t go deep into the water. Even lightning only travels to a depth of about 20 feet before dissipating.
• salinity - The more salts in the water, the more and wider it will be easily electrified. Seawater floods have high salinity and low resistivity (typically ~22 ohmcm compared to 420k ohmcm for rainwater).
• Temperature The warmer the water, the faster its molecules move. Therefore, the electric current will also be easier to propagate in warm water.
• Topography – The topography of the area can also matter.
• Path – The risk of electric shock in water is high if your body becomes the path of least resistance for the current to flow. You are only relatively safe as long as there are other lower resistance paths around you.
• touch point – Different parts of the body have different resistance. For example, the arm typically has a lower resistivity (~160 ohmcm) than the torso (~415 ohmcm).
• Disconnect device – The risk is higher if there is no disconnecting device or if there is one and its reaction time exceeds 20 ms.

Calculation of the safety distance

Estimates of the safe distance can be made based on codes of practice for the safe use of electricity underwater and research in underwater electrical engineering.

Without a suitable release to control the AC current, if the body current is not more than 10 mA and the body trace resistance is 750 ohms, then the maximum safe voltage is 6-7.5V. [1] The values ​​of the safety distance in water depend on the ratio of the fault current to the maximum safe body current (10 mA for AC, 40 mA for DC):

• If the AC fault current is 40A, the safety distance in sea water will be 0.18m.
• If the power line is down (on dry ground), you must stay at least 33 feet (10 meters) away, which is about the length of a bus. [2] In water, this distance will be much longer.
• If the toaster falls into water, you must be within 360 feet (110 meters) of the power source. [3]

How can you tell if water is electrified?

Besides the question of how far electricity travels in water, another important related question would be knowing how to tell if water is electrified.

cool fact: Sharks can detect as little as 1 volt difference a few miles from a source of electricity.

But how can we know if current is flowing at all?

If the water is highly electrified, you may think that you will see sparks and bolts in it. But it's not. Unfortunately, you won't see anything, so you can't tell just by seeing the water. Without a current testing tool, the only way to know is to get a feel for it, which can be dangerous.

The only other way to know for sure is to test the water for current.

If you have a pool of water at home, you can use the shock alert device before entering it. The device lights up red if it detects electricity in the water. However, in an emergency, it is best to stay as far away from the source as possible.

Take a look at some of our articles below.

• Do night lights use a lot of electricity
• Can electricity pass through wood
• Nitrogen conducts electricity

Recommendations

[1] YMCA. A set of rules for the safe use of electricity under water. IMCA D 045, R 015. Retrieved from https://pdfcoffee.com/d045-pdf-free.html. 2010.

[2] BCHydro. Safe distance from broken power lines. Retrieved from https://www.bchydro.com/safety-outages/electrical-safety/safe-distance.html.

[3] Reddit. How far can electricity travel in water? Retrieved from https://www.reddit.com/r/askscience/comments/2wb16v/how_far_can_electricity_travel_through_water/.

Video links

Rossen Reports: How To Spot Stray Voltage In Pools, Lakes | TODAY