Winterizing a water system means keeping the water in it from freezing, because water expands by about 9% as it turns to ice and splits pipes and fittings: bury every line below the frost line, 0.5 m in mild areas and 1.5 m or more in severe cold, fit drain valves at every low point, insulate above-ground tanks, and shut down and drain any section that will freeze regardless.
Part of Water Distribution
Winterization is the set of design choices and seasonal routines that keep a water network from freezing, and from being damaged by the ice when it does. A frozen line is also a line with no water for the people who need it.
Ice Needs More Room Than Water, And Pipes Do Not Give
Water expands about 9% in volume when it freezes. A closed, full pipe or fitting has nowhere to put the extra volume, so it splits, usually at the weakest point, and the break only shows when the ice thaws. The protection is to keep the water above freezing, or to take it out of the pipe.
The water-distribution page lists four measures:
- Bury pipes below the frost line. The depth varies: 0.5 m in mild areas, 1.5 m or more in severe cold (Burial Depth).
- Install drain valves at every low point so exposed sections can be emptied (Drain Points).
- Insulate above-ground tanks with straw bales, earth or foam.
- Drain and shut down any section that will freeze regardless. Better to lose one tap than the whole system.
What You Need
- Local frost depth, found by asking residents or digging in late winter
- Drain valves, shut-off valves and a map showing which are which
- Insulation: straw bales, earth or foam, kept dry
- A winter checklist and someone to run it before the first freeze
Method: Before The Freeze, And During It
Step 1: Before winter, walk the route (Visual Inspection) and note any pipe that is shallow or exposed.
Step 2: Insulate or cover tanks, risers and exposed fittings.
Step 3: Decide which sections will be shut down and drain them through their drain points, opening a high vent so air can enter.
Step 4: During cold snaps, check the tank and exposed taps daily.
Step 5: In spring, refill slowly, vent air, and check every joint for splits before relying on the line.
Worked Example
A full 25 mm pipe holds π × 0.0125² = 0.000491 m² × 1 m = 0.491 L per metre. If it freezes solid, the ice occupies 0.491 × 1.09 = 0.535 L, 0.044 L more than the pipe volume, per metre. That is a small volume, but it has to go somewhere, and the only places are the pipe wall and the fittings.
Common Mistakes
- Leaving a tap with water behind it in a freezing spot. It splits.
- Draining a section without opening a high vent. Water does not drain out of a closed pipe.
- Insulation that gets wet. It stops insulating.
- Refilling fast in spring. Surge and trapped air damage cracked fittings.
Tip
A dripping tap does not freeze as readily, since moving water resists freezing. In an emergency, leave the most vulnerable tap open slightly overnight. This is a stopgap, not a design strategy, and it wastes water.
What’s Next
- Learn next: Burial Depth — how deep to bury a line
- Combine with: Drain Points — emptying exposed sections