Lake water and your home: what’s safe and what’s not?
March 27, 2025
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Whether you’re considering using lake water in New Hampshire to drink, water your lawn and garden, or set up a splash pad for your kids and pets, it’s good to know the risks and best practices. This guide answers commonly asked questions about safely using lake water, so you can enjoy another benefit of New Hampshire’s lakes!
Is it safe to drink lake water? What if it’s filtered or boiled?
- You should not drink untreated lake water. Even in clean lakes, water can contain bacteria (like E. coli), parasites, viruses, and potential toxins from cyanobacteria blooms that can make you unwell.
- To make lake water drinkable, a multi-step treatment process should be used at a minimum, including sediment filtration, activated carbon, and disinfection (boiling, UV treatment, or chemical purification). However, this treatment process may not be enough to remove toxins produced by some cyanobacteria blooms, and may actually make the water more toxic.
- The New Hampshire Department of Environmental Services (NHDES) strongly cautions against using lake water for drinking. Read more here.
How is my house filter system different than the community facility’s system? The facility pulls drinking water from the river or a reservoir, so how is that different from my system pulling water from the lake?
- Drinking water facilities use large-scale treatment systems that remove bacteria, chemicals, and contaminants through coagulation, sedimentation, filtration, and disinfection. Processes that drinking water facilities use, such as chlorination, ozone, or UV treatment, kill bacteria, viruses, and parasites.
- Drinking water facilities continuously test the water to meet the Environmental Protection Agency and state drinking water standards.
- Drinking water facilities may have mechanisms to manage the source water (reservoir, river, etc.) for drinking water purity, including monitoring and controlling algae and cyanobacteria growth. An alert system may also be in place to prevent using the source water if it becomes contaminated with potentially toxic cyanobacteria blooms. Read more about cyanobacteria and public drinking water systems here.
Can I use lake water to water my vegetable or herb garden (a.k.a. edible plants)?
- Use the NHDES Healthy Swimming Mapper, to learn if a water quality alert is issued for your lake. Plants, particularly leafy greens and root vegetables can absorb bacteria (like fecal coliform) or toxins from cyanobacteria. A water quality alert for your lake does not necessarily mean that the whole lake is unusable. Be aware of how the water looks around your intake from the lake. If you see green scum or what looks like pea soup on the surface of the lake in your area, do not use lake water to water edible plants.
- Apply water to the soil, not directly to the plant. Drip irrigation and soaker hoses reduce the risk of bacteria splashing onto or coming into contact with edible parts.
- Consider filtering and treating the water before use, especially if you pull water from a shallow area where bacteria and algae are typically more concentrated.
Can I use lake water to water my flower garden (a.k.a. non-edible plants)?
- Yes, lake water is generally safe to use, even without treatment. Ornamental plants are not at risk of contamination from bacteria (like fecal coliform) or toxins from cyanobacteria blooms in the same way as edible plants.
- Sediment and nutrients in lake water can benefit plant growth. The nutrients can act as a mild fertilizer. If the water is murky or contains algae, let it settle before use, or use a mesh filter to remove debris.
- Avoid using lake water after heavy rain, which may include polluted runoff from roads or lawns. It’s more likely to be contaminated with chemicals like pesticides and herbicides that could harm plants.
Can I use lake water to water my lawn or yard?
- Yes, lake water is generally safe to use, even without treatment. Lawns are not at risk of contamination from bacteria (like fecal coliform) or toxins from cyanobacteria blooms in the same way as edible plants in your vegetable or herb garden.
- If you plan to water the lawn with a sprinkler, especially if kids or pets play in the yard, consult the NHDES Healthy Swimming Mapper, to learn if a water quality alert for bacteria (fecal coliform) or a potentially toxic cyanobacteria bloom is listed for your lake. A water quality alert for your lake does not necessarily mean that the whole lake is unusable. Be aware of how the water looks around your intake from the lake. If you see green scum or what looks like pea soup on the surface of the lake in your area, do not use lake water to water your lawn or yard.
- If you forage from your lawn or yard, exercise the same caution as you would in a vegetable or herb garden.
- Sediment and nutrients in lake water can benefit plant growth. The nutrients can act as a mild fertilizer. If the water is murky or contains algae, let it settle before use, or use a mesh filter to remove debris.
- Avoid using lake water after heavy rain, which may include polluted runoff from roads or lawns. It’s more likely to be contaminated with chemicals like pesticides and herbicides that could harm plants.
Is lake water safe for pets to drink or play in?
- Lake water is as safe for pets as it is for humans. Just like us, pets can get sick from drinking untreated lake water. Sometimes, pets are more susceptible to water quality issues, like cyanobacteria blooms.
- Use the NHDES Healthy Swimming Mapper, to learn if a water quality alert bacteria (fecal coliform) or a potentially toxic cyanobacteria bloom is listed for your lake. A water quality alert for your lake does not necessarily mean that the whole lake is unusable. Be aware of how the water looks around your intake from the lake. If you see green scum or what looks like pea soup on the surface of the lake in your area, do not use lake water for kids or pets to play in.
- NHDES strongly caution against drinking lake water. Read more here. Stagnant or murky water can also contain parasites like Giardia, so it’s best to provide pets with fresh water intended for drinking.
Can I use lake water for my shower?
- It depends! A basic filtration system can help reduce contaminants like sand or muck. Use the NHDES Healthy Swimming Mapper, to find out if your lake is under a water quality alert for bacteria (fecal coliform) or a potentially toxic cyanobacteria bloom. Basic house filters don’t remove toxins produced by cyanobacteria blooms, which can irritate the skin and cause rashes.
- Bathing directly in the lake is not advised. Soap and shampoo should never be used directly in the lake, even if they are biodegradable. If not in a designated outdoor shower, bathe in an area where wash water will not flow into the lake.
Can I use lake water for household facilities (flushing toilets, laundry, dishes, etc.)?
- Many lakeside properties pump lake water for non-drinking uses, like flushing toilets. A basic filtration system can help reduce contaminants like sand or muck.
- A basic filtration system may not be sufficient to remove contaminants like bacteria (fecal coliform) or potentially toxic cyanobacteria that can make you unwell for tasks like laundry or dishes.
- Use the NHDES Healthy Swimming Mapper, to find out if your lake is under a water quality alert for bacteria (fecal coliform) or a potentially toxic cyanobacteria bloom. A water quality alert for your lake does not necessarily mean that the whole lake is unusable. Be aware of how the water looks around your intake from the lake. If you see green scum or what looks like pea soup on the surface of the lake in your area, do not use lake water in your home.
How can I tell if lake water is safe to use?
- Check for active advisories. For updates, visit New Hampshire Beach Advisories and the Healthy Swimming Mapper, both managed by NHDES.
- Look at the condition of the lake. If the lake or water looks like pea soup, blue-green paint, or antifreeze, avoid using it and report it to NHDES using their cyanobacteria bloom reporting tool.
- Pay attention to changes in the taste and odor of the lake water you use in your home. They may indicate an issue.
- Be aware of recent weather. Heavy rain can introduce bacteria, pesticides, and other pollutants into the water. If there’s a concern for the water quality near your lake intake, consider avoiding using the lake water for a day or so after a storm event.
by Ale Consulting