We don't have synonyms for drywell yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are drywall and dry well.
(n) :
Alternative form of dry well. [(civil engineering, construction) An underground structure (for example, a pit filled with gravel) that disposes of unwanted water (most commonly surface runoff and stormwater and in some cases greywater) by holding it and dissipating it into the groundwater.]
(n) :
Alternative form of dry well. [(civil engineering, construction) An underground structure (for example, a pit filled with gravel) that disposes of unwanted water (most commonly surface runoff and stormwater and in some cases greywater) by holding it and dissipating it into the groundwater.]