Do you have any tips for buying a UV water system for the cottage?

Do you have any recommendations for buying a UV water system for the cottage? I want to draw my drinking water from the lake instead of bringing it with me.

—Tom Howell, Duck Lake, Ont.

First of all, let’s go back to biology class. The UV light destroys microorganisms by gluing parts of their DNA together, which prevents the double-helix strand from “unzipping” for replication. No DNA replication means no reproduction.

Your UV system should have a flow rate of eight gallons per minute (this size will suit most cottages), a lamp strength of 40 millijoules/cm² or more, and a light output of 254 nanometres. Look for systems with an NSF 55A or a CSA B483 certification, says Jerry Capko, manager of the safe water program with the Simcoe Muskoka District Health Unit.

You’ll need to pre-filter the water, though. “The UV is there for one thing only: to keep you safe from water-borne illness,” says Larry Miller of DSMI/Passport Water Purification Products in Thornton, Ont. If the water isn’t clear enough, the light can’t penetrate the viruses and bacteria.

At minimum, you’ll need a five-micron sediment filter to reduce turbidity from dirt and algae, says Scott Macdonald, president of Envirogard, a company that manufactures water filters and purifiers in Richmond Hill. You may need other filters—for example, a carbon filter to remove tannins that darken water (colour blocks the light), or a greensand filter for iron and manganese, which can stain the quartz sleeve covering the unit’s bulb and reduce the system’s effectiveness.

A typical UV system costs between $500 and $1,500 (the more expensive ones include alarms that tell you when to replace the bulb). It’s worth installing electrical protection (surge protector, voltage regulator, uninterruptible power source) to handle power fluctuations—that’s about $60 to $100. Tack on $20 to $50 for a sediment filter, and up to $2,000 for additional pre-treatment.

You’re probably saying, “Never mind, I’ll just drink beer.” Don’t worry: Many people who use UV need only the sediment filter, say our experts.

Capko has a tip: If lake neighbours use a UV system, find out how they pre-treat the water, and ask to see their sample results. “Everybody’s straw is in the same trough. If they’re not turning green and growing a second head, it’s probably working out for them.”


Published in the June 2011 issue of Cottage Life.