How Deep Should a Well Be for Drinking Water?

How Deep Should a Well be for Drinking Water

There are plenty of benefits of owning your own private well.

You’ll pay less for your water, increase the value of your property, and have unlimited access to as much water as you could want.

When you’re looking at installing a well, the depth of the well is an important consideration to make.

Your well needs to be deep enough to reach an underground reservoir known as an aquifer, which will collect water that pumps up to the surface. Located at the bottom of the casing is a seal, which will prevent pathogens from entering the ground water through the bedrock.

If you’re at the point of installing a dug well, it’ll need to be between 100 and 500 feet deep. Sometimes a well water source may even reach up to 1,000 feet deep.

Why such a wide range?

The actual depth of the well will depend on several things, which I’ll be looking at in more detail in this article.

Factors Affecting How Deep a Residential Water Well Needs to Be

Depth of Aquifer

Wells get their water from underground aquifers – or pockets of water inside the bedrock.

Your well needs to be deep enough to get access to this water, so the depth of the well you need depends on how far below ground your aquifer is.

Typically, well drilling needs to reach at least at the 300-500 deep feet range to hit the bedrock, though on some occasions, a well may even need to reach 1,000 feet.

See this article to find out more information about aquifer depth in your region.

how deep is a well

Risks of Surface Contamination

Generally, if your well is properly constructed (i.e. it’s solid, durable and protective against harsh environments), it’ll provide better protection the deeper it’s installed.

If you have a longer well depth and more well casing, water will take longer to flow from the aquifer to the well pump.

This longer traveling time gives a higher likelihood of any bacteria and other health-harming contaminants dying off or getting trapped in soil along the way, reducing the risk of contamination of the well’s surface water.

👉 Read my full guide on well water treatment here.

Geology of Bedrock

The geological characteristics of the bedrock below your property will have an impact on the location of the aquifer, which will in turn affect the well depth.

Rock formations that are low-yielding will likely require especially deep well drilling, to allow the well to act as a storage chamber for groundwater.

The geology of the rock your well will be drilled through may also determine the size of the well, which will have some effect on its depth.

bedrock geology

Water Quality

Certain areas in the US have “cased off” zones that wells cannot be drilled into because of poor water quality.

In this case, you may require a deeper well depth to avoid these zones and prevent dangerous contamination of your water.

Your well driller/drilling company or local authority should be able to provide information about your water supply, including any changes in the depth of the water table and the quality of your ground water.

If you’re drilling a deep water well for better water quality, make sure to factor in plenty of time – it usually takes a full day to get the well, cap and casing properly installed, and an extra day to install the well pump.

Related: Ultimate Well Water Testing Guide (updated for 2021)

Seasonal Fluctuations of the Water Table

If your local area’s water table fluctuates with the seasons, you might have to drill your well much deeper than anticipated to be sure you always have access to a ground water supply, regardless of water levels.

Again, you can search for information about your water level, and how it may be related to the required diameter of nearby wells, online.

Governmental Regulations

Depending on the state you live in, there might be certain regulations you have to follow relating to well depth. Be sure to check out these specific guidelines and rules before drilling a well.

Generally, you’ll have to have casing that reaches at least the 20 foot mark, which typically needs to reach the bedrock. You’ll have to properly seal the outside of the well casing, too, to stop sand and sediment from getting into the system.

Remember, how deep your well is will affect a number of drilling factors, such as cost, pump placement, the well’s diameter, water levels, and perhaps even water yield (in gallons per minute). A shallow well will naturally cost less to be drilled than deeper wells, and drilling a shallower hole into less rock will take less time.

In your search for a company to drill your well, look for one that has extensive experience in the industry, and you shouldn’t go wrong. Keep in mind that the majority of companies charge per foot drilled, so depending on the above considerations, it could be an expensive job. Learn more about finding a contractor at wellowner.org.