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We use a sump pump hose that I got at Home Depot for around $10.I run the hose into the yard and put the hose into the tub. I turn on the whirlpool jet full blast and hold the hose in front of it. It gets a really good flow going. After about 10 seconds or so I kill the power and gravity does the rest. Our tub is close to 500 gallons and we empty in 15 minutes this way.
How we drained our tub..is we have a hose that is really old, hubby has fixed leaks in it about 5 times, so he takes it apart (it's hooked together by repair kits) and waaaa laaa we have 5 seperate hoses to siphon water from the tub. Takes about 15 min to drain then the rest of the water that is in the tub I drain with an old fashioned cup and bucket till my back tells me I can't do no more and hubby yells at me to get out of the tub that I'm only going to make my back worse! Anyway that's another story for another day!