Dewinterizing Your Seasonal Water System

Turning Your Water Back On

The summer months are rapidly approaching, which means that Maine’s cold winter has come to a close. Now you’ll want to get started with turning your seasonal water system back on. After effectively winterizing the property in the fall, it’s time for dewinterization. 

Note* The easiest way to dewinterize a property that was winterized by a professional is to have the same individual return and perform the service. They should be aware of exactly what was done and the process needed to get things back up and running again.

Maine CDC Drinking Water Program (Seasonal Water Systems)

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In the State of Maine, Many water systems only operate for part of the year. Examples include: campgrounds, summer camps, restaurants, sporting camps, ski areas, golf courses, and motels. These systems often open and serve drinking water to the public after hibernating for part of the year. If you operate a seasonal system use this guide to help avoid problems with your system.

  1. Inspect your well: If you do not have a sanitary sealed well cap or if the well cap is loose, take off the well cap and check to see if there is debris inside. Use a shop vacuum to remove any unwanted material. Bugs and other critters can introduce bacteria into the water system. If your well cap does not seal, replace it with a new one. Ask your public water system inspector about the Drinking Water Program’s Sanitary Seal Well Cap program. Remember, the Ground Water Rule says that you must have a sample tap before your pressure tank, so you can collect source samples if your water tests positive for coliform.
  2. Disinfect the system: Water in your pipes and in your well sits over the winter and stagnates. If you’ve drained the system, there’s a good chance that bacteria have moved in. You can kill bacteria by adding bleach to your well. You must use bleach that has been approved for disinfecting drinking water (e.g. Clorox®). Guidance for disinfection can be found in our ‘Well Shocking Fact Sheet’ which is located on our website at: Many systems break apart sections of water lines in the fall to ensure they are drained. You can help speed up disinfection by adding bleach directly into the water pipes before re-connecting.
  3. Run your well to fill the system: Turn on faucets at the ends of the system to push chlorinated water into all of the pipes. When you can smell chlorine coming out of the taps, shut the water off and let it sit overnight. Chlorine works best if it is allowed to stay in contact with contaminated materials overnight.
  4. Flush your tanks: Be sure to drain and refill your water storage tanks to remove rusty water and ensure that the valves still work. Continue flushing until the water is no longer discolored.
  5. Walk your pipes: If you have lines that run over the ground, take a walk around to make sure that they are not leaking. Leaking lines may result in bacteria entering the system and can increase your power costs. It can also run your well dry.
  6. Wait a week before taking bacterial samples: We strongly encourage collecting an Operations and Maintenance (O&M) total coliform bacteria sample to ensure your efforts to prepare for the season have been successful. O&M samples do not count toward annual testing requirements. If the samples are “bad” they will not count against you. However, if the results are good you cannot use the results for compliance purposes.
  7. Collect your initial compliance samples within 30 days of opening as required by the State Drinking Water Regulations. Refer to the Annual Testing Requirements Letter that was mailed to your system for the required water tests and frequencies that will be due during the operating season.
  8. Remember: Seasonal water systems must perform a State-approved startup procedure and provide certification to the DWP that they have met that requirement. Certification must be completed and sent to the DWP before serving water to the public.

If you have any questions regarding the compliance requirements for your system, call your public water system inspector at 287-2070.

Approved Annual Startup Procedure for Maine Seasonal Public Water Systems Using Groundwater

Startup Procedures Form (PDF)

Certification Of Completion Of Annual Startup Procedures (PDF). The following startup procedure is approved by the Maine Drinking Water Program in accordance with the Revised Total Coliform Rule for seasonal water systems using a groundwater source. Any startup procedures for seasonal public water systems that do not include the elements in the procedure outlined below must be pre-approved by the water system’s DWP Public Water System Inspector.

Wrap Up

For homeowners, don’t hesitate to bring in professional services to assist with the winterization process if you have any questions. You and your family’s safety should always be first and foremost. For businesses in the State of Maine – failure to submit the above certification before you open and begin serving water to the public may result in drinking water violations and increased Total Coliform monitoring requirements. Protect your customers and business by staying compliant.

Works Cited

Drinking Water Program, Maine CDC. “Maine CDC Drinking Water Program Starting up …” OpeningSeasonalWaterSystem, Mar. 2018,

DWP, Maine. “Approved Annual Startup Procedure for Maine Seasonal …” DWP-Startup-Procedure, n.d.,

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