- 18th-19th century stone-lined pit which held the balance bob for a pump-rod or flat-rod system. It includes examples where the surviving feature is a pillar for the bearing, rather than the pit.
- English Heritage
- http://creativecommons.org/licenses/by/3.0 (FISH Thesaurus of Monument Types)
- http://www.english-heritage.org.uk (FISH Thesaurus of Monument Types)
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