If the original manual didn't mention the drain pipe, you would modify it beyond the scope by adding the drain pipe. If it is a utility model patent, there is no way out, so we can only resubmit or apply for another patent; If it is an invention patent, it can be amended after the invention patent is put forward for real trial or the notice of entering the real trial is obtained.
In addition, the addition of the appended drawings will change the application date and application number of this patent.