The Iwaki 70RLT is rated at 1536gph @0' head with a shut off head of 32'. The Blueline/Panworld pump is rated at 1750gph @ 0' head and has a shut off head of 39'. Unfortunately, the price is about the same for either one. If you had a valved tee in the pressure line coming from the pump running to a drain, you could easily pump out water from the sump to the drain. Then, if your SW
mixing container was sitting close to the sump, you could pump new SW
into the sump. It would be pretty easy to set up.