My wifey and I both have bad knees so I've been thinking about a hi profile toilet. I added a sprayer to my current toilet and a LOT of water goes down the drain when flushing AND using the sprayer... fresh water tank goes down and black water tank fills up fast! Does the Dometic with the mfgr. installed sprayer shut off the flush water when the sprayer is used? If not Dometic, does any other brand do that? Thanks,Craig