Other

Oliver M Knutson

Donald C Watson

Craig S Gaul

A device for a drain, such as a manhole 10 for access to a sewer, is protected by a seal structure 34 having a bottom bleeding feature such as a bottom thru-bore 42. The seal structure 34 may have a flange 38 for sealingly engaging between a cover 22 and a frame 18 around an accesshole 17 of the manhole 10. The structure 34 has a central portion downwardly depressed to avoid a path of spin of the cover 22. In a bottom portion 40 of structure 34, the thru-bore 42 bleeds (such as by thin trickling streams) into and off the sewer, sufficient fluids such as air to maintain a substantially atmospheric level of pressure in the sewer. Because of its size and shape, the thru-bore 42 advantageously bleeds into the sewer, from water introduced to manhole 10, only quantities of water known to be tolerated by the sewer system. To avoid unsanitary conditions, when water stops entering accesshole 17, the thru-bore 42 substantially completely drains away water remaining in the seal structure 34.

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Sinking Spring, PA, United States of America

Oliver M Knutson