Done. Hmm ! $150 each. I'd need two of these. Unless..... I used just one for Black tank, and kept the grey valve always open, using block. When it came time to flush Black, remove block (easy), push button, black tank flushes. Open up hot water in kitchen, run it for a while to clean out outside sewer hose and Y junction. Push button. Black tank closes. Turn off kitchen tap. Replace block. Easy. Need to think about it for a while. Thanks. Never knew the remote ones existed !
I might use the manual ones plus block for a while to see how it works out.