I have a slide that requires 20GPH. The way the builder ran the plumbing I have to run my pump at 3000rpm just to get water to the slide. This is after the PB put restricters in all 4 returns... I don't want to spend the money on running my 1.5hp pump just to use the slide... and I would like to not have restricters in the returns either... So I thought I would use a pump inline just before the slide. This would pull water from the returns when the main pump is off and from the filter when the main pump is running... So what pump do I need to get 20gpm at 12 to 15 ft of head?