mrwalt Report post Posted December 26, 2023 The kitchen sink in my motorhome has started to stink. Is there a drain cleaner that can safely be used and will not be detrimental to the gray water tank. Share this post Link to post Share on other sites
sandyhepburn Report post Posted December 26, 2023 It may be the grey tank itself that is causing the stick - there are grey tank cleaners on the market that are similar to black tank products that can be used to address the issue. Share this post Link to post Share on other sites
rayin Report post Posted December 26, 2023 (edited) Under the sink in the waste plumbing should a an air-admittance valve on top of a vertical stand-pipe. It's function is to prevent any negative pressure from sucking the standing water from the "P" trap. If this water is not present, vapors from the gray tank can escape and might smell worse than the black tank odors. If this valve is faulty it will not prevent that negative pressure. Edited December 26, 2023 by rayin Share this post Link to post Share on other sites
