Lake Simcoe looks clean from the dock, and on a calm day you can see the bottom. That does not make it safe to drink straight from the intake. Here is why, what a proper cottage treatment system does about it, and how to bring one back into service each spring.
The short answer
Not untreated. Lake water, like any surface water, has no layer of soil and rock filtering it the way groundwater does. The Province of Ontario says surface water should be considered unsuitable for drinking without treatment, on its testing and treating private water wells page. With the right treatment, and a system that is maintained, lake water can supply a cottage kitchen safely.
This article is about private lake intakes: the cottages and waterfront homes around the lake that pump their own water. Towns such as Keswick that are on municipal supply get Lake Simcoe water that has already been treated at a plant.
Why untreated lake water is not safe
Clarity tells you nothing about safety. The problems in lake water are mostly too small to see:
- Bacteria from waterfowl, wildlife, pets, runoff and septic systems along the shore.
- Parasites such as Giardia and Cryptosporidium, which are hardy and can cause illness in small numbers.
- Viruses that come from the same sources as bacteria.
- Sediment and organic matter, which stir up after storms and in spring, and which shield microorganisms from disinfection.
- Algae and blue-green algae blooms in warm, calm weather. Some blue-green algae can produce toxins that ordinary cottage treatment and boiling do not remove.
Water quality at an intake also changes with wind, depth, season and what is happening along the shore. A single good result is a snapshot, not a guarantee.
How a cottage intake system makes lake water drinkable
Every system is designed around the water and the building, but the stages follow the same logic: take out what you can see, then take out what makes the water taste and smell, then disinfect what is left.
1. The intake and pump
A line runs out into the lake, ideally deep enough and far enough from shore to avoid the warmest water and the stirred-up shallows, with a screen or foot valve at the end. The pump feeds a pressure tank in the cottage.
2. Sediment filtration
One or more sediment cartridges catch sand, silt and algae, usually a coarser stage followed by a finer one. This matters more than people expect: particles in the water shelter microorganisms from UV light, so clear water going into the disinfection stage is essential.
3. Carbon
A carbon stage improves taste and odour and reduces organic compounds that give lake water its earthy or fishy smell.
4. UV disinfection
UV disinfection is the barrier that deals with bacteria, parasites and viruses, without adding chemicals to the water. It only works if the water reaching it is clear and the lamp and sleeve are maintained.
5. Drinking water at the kitchen tap
Many cottage owners add reverse osmosis at the kitchen tap as a further barrier for the water they drink and cook with.
Our cottage and lake water systems page covers how we size and lay out each of these stages for a particular property.
Seasonal start-up
A cottage system that sat drained over winter is not ready to drink from the day you open the cottage. A careful spring start-up looks like this:
- Check the intake line, screen and foot valve for damage or ice movement, then prime and start the pump.
- Fit new sediment and carbon cartridges. Last year's cartridges have sat wet or dry all winter and are not worth trusting.
- Install a new UV lamp and clean or replace the quartz sleeve. Lamps are changed once a year, and spring start-up is the natural time.
- Disinfect the plumbing downstream of the UV, because the pipes, fixtures and any tank can harbour growth after sitting over winter.
- Flush every tap until the water runs clear and any disinfectant has cleared.
- Test before you drink. Have a bacteria sample taken after start-up, ideally from the kitchen tap after the treatment, and use bottled water until the result is back.
In the fall, the reverse: shut down, drain the lines, pressure tank and filter housings so nothing freezes, and leave the system ready for spring.
Around the lake
We service cottage and waterfront systems around the south and east shores of Lake Simcoe, including Georgina, Beaverton and Brock Township, Innisfil and the Keswick shoreline. If you are not sure what your intake is delivering, in-depth well water testing is the place to start: bacteria, iron, sulphur, hardness and a lab panel on the water your intake actually draws, and the filter and lamp change schedule covers what to keep up through the season.
Common questions
Can you drink Lake Simcoe water if you boil it?
Boiling kills bacteria, parasites and viruses, so it is the right emergency step. It does not remove sediment, chemicals or algal toxins, and it is not practical for a whole cottage. For everyday use, a proper treatment system is the answer, and during a blue-green algae bloom follow the advice of your local public health unit rather than relying on boiling.
Is a UV system enough for lake water?
Not on its own. UV needs clear water to work, so lake water must be filtered first. Sediment filtration, then carbon, then UV is the usual minimum, with the lamp changed every year.
How do I test my cottage lake water?
For bacteria, ask your local public health unit about testing for your water source, or use a licensed laboratory. Test after spring start-up, after any repairs, and whenever the water changes. For chemical questions, a licensed lab panel is the way to go.
Is it safe to drink the tap water when I first open the cottage?
Not until the system has been started up properly: new cartridges, a new UV lamp, disinfected and flushed plumbing, and a clean bacteria result. Until then, use bottled water for drinking, cooking and brushing teeth.
What about blue-green algae?
If there is a bloom near your intake, do not use the lake water for drinking or cooking, even if it goes through your treatment system, and follow the advice of your local public health unit. Standard cottage filtration and UV are not designed to remove algal toxins.
Do I need a different system for a year-round waterfront home?
The stages are the same, but year-round use changes the maintenance schedule and how the intake line is protected from ice. We design for how the property is actually used.