These little transfer pumps are workhorses,, are quiet and efficient. You can spend much less than what this one costs and they come in 12volt options as well. https://www.amazon.com/WAYNE-PC4-Multi-Purpose-Suction-Strainer/dp/B0002YQUBM/ref=mp_s_a_1_6?adgrpid=55725766973&dchild=1&gclid=Cj0KCQjwytOEBhD5ARIsANnRjViy_aDCTZChyrm0R658kh2khJhnsPsYwAEJrbmmF5WRkZd2WEvfc5YaAlsAEALw_wcB&hvadid=2747480...
I actually bought a pump from Amazon that I have yet to try that takes a hose attachment. I am considering attaching it to the drain to suck the water out of the tub through its drain attachment and push it into my drain system. I can’t endorse the idea yet because I haven’t tried it, but it should speed up draining dramatically.
WAYNE PC4 1/2 HP Cast Iron Multi-Purpose Pump With Suction Strainer, Model:55832 https://www.amazon.com/dp/B0002YQUBM/ref=cm_sw_r_cp_api_glt_fabc_782ZDJJEN2H7YBRCCMHY?_encoding=UTF8&psc=1
I bought this one several years ago. (Was only $99 then) It's still going strong. Routinely empty my barrels on the downspouts into the 3 that I have in my garden ~50' away and 4 feet up on a platform. It will push about 40 gals. of water in ~5-10 min.