Definition - What does Lid Plugs mean?
Lid plugs are used to plug holes in manhole lids to prevent the inflow of water into a system. Manhole covers are an integral part of a sewer system, as they provide access to service personnel for the purpose of cleaning and repairs.
Leaky manhole covers can allow rain water to enter a sewer system in monsoon and overload sewer treatment plants. It can also allow salt and other chemical substances used to melt snow in the winter to enter the manhole and the sewer pipeline. These chemicals can cause corrosion and other damage to connections inside the manhole.
Trenchlesspedia explains Lid Plugs
Previously, manhole covers were manufactured with holes in them for the purpose of venting vapor or gasses from the sewer that would be trapped in the manhole. These holes were made varying in size from less than 1" to 1 1/2" in diameter and from 2 to 40 in numbers.
The tapering of these holes is a truncated cone with the smaller diameter at the top and the larger diameter at the bottom of the manhole. These holes are no longer considered necessary and have become a cause for concern as it allows entry of water into the sewer system. Lid plugs are used for the purpose of plugging these holes. These plugs are made of a thermoplastic material that is moldable and has high heat distortion temperature, is abrasion resistant and has high tensile strength.