... Minimum lifespan of 30 maintenance free years. 5. Well sealed ---It can be used hermetically, and effectively ... prevent those poisonous gases leaking out from cesspool. Well sealled, no noise pollution or rebound. 6. ... well; Post, telecommunication, communication pipeline well; (2)Street lamp well, fire control well, all kinds of valve well; (3)City water, drainage pipeline well; Heat supplied, gas well ...