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RV (and home) hand held shower heads are designed to NOT shut off 100%. That is to alleviate the above mentioned problem of getting scalded. I worked in the home improvement industry for years (as well as being an RV owner) and you would not believe how many people were dissatisfied or wanted to return their new shower attachments because they leaked. LOL.
Do NOT turn the water off 100% when soaping and scrubbing. If you do you can get scalded when you turn the water back on. Hot water will rise into the feed pipe to the shower head (heat rises and cold drops) so when you turn it back on you will get a blast of JUST HOT WATER. if you let it just dribble a little the hot and cold stays mixed and no problem while still saving lots of water.