What is base-can drainage?
Letting water leave a light base can instead of collecting in it — a drain hole, a free-draining bed below and a drain pipe laid to a fall — so the transformer and connectors are not left standing in water.
Base-can drainage is the arrangement that lets water leave a light base can. It normally means a drain hole in the can, a free-draining bed or sump below it, and a drain pipe laid to a fall that carries the water to an outlet, all as the design specifies.
A base is never perfectly sealed, so some water is expected. If it cannot drain, it stands around the isolating transformer and connectors and can cause insulation faults, corrosion and earth faults on the series circuit. The drain is easily blocked, most often by grout, silt or debris, so protect the opening while grouting and prove it clear afterwards. Keep loose material off the airfield surface, treat any cable in or near the can as live until the circuit has been isolated, locked out and proved dead, and work to the airport’s permit-to-work.
- Expect water. Seals and joints let some in, so the base is designed to drain.
- Keep the drain hole open. Check it is clear and protect it during grouting.
- Provide the bed. Place the free-draining bed or sump the design shows below the can.
- Lay the drain pipe. Lay it to the specified fall, without kinks or low spots.
- Connect the outlet. Connect to the drainage line, soakaway or outlet the design shows.
- Flow test. Pour water in, confirm it leaves steadily and record the result.
Frequently Asked Questions
Q1What is base-can drainage in airfield ground lighting?
Base-can drainage is the arrangement that lets water leave a light base can instead of collecting in it. It normally means a drain hole in the can, a free-draining sump or bed below it, and a drain pipe or soakaway route to an outlet, all as the design specifies.
Q2Why does water get into a base can?
Rain and surface water can pass the fixture seal, the connectors and the joint between the can and the pavement, and groundwater can rise around the can. Some water in a base is normal, which is why the base is designed to drain rather than to be perfectly sealed.
Q3What happens if a base can cannot drain?
Water stands around the isolating transformer and the connectors. That can cause insulation faults, corrosion and earth faults on the series circuit, and in cold climates standing water can freeze and push against the can and fixture. A blocked drain is a common hidden cause of repeat faults at one light.
Q4How is drainage normally provided?
A drain hole or outlet at the bottom of the can lets water out into a free-draining bed or sump below it, and a drain pipe laid to a fall carries the water to a drainage line, a soakaway or another outlet. The exact arrangement, bed material and fall come from the design and the can manufacturer’s data.
Q5Why must the drain be protected during grouting?
Grout is designed to fill and bond, so it can easily run into the drain hole or the bed below and block it. Cover or plug the opening as the method statement requires, remove the cover afterwards, and confirm the drain is clear before the work is signed off.
Q6How is a base-can drain checked?
Pour clean water into the can and watch it leave at a steady rate, check the outlet runs clear, and look for silt or debris in the bed. Repeat the check during routine maintenance and after heavy rain, as your site’s inspection procedure requires.
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