Pumps actually work less with higher pressures. Flow rates go down, energy use goes down, but slower, so efficiency (gallons/watt-hr) goes down as well. A pump has a maximum head/pressure that it can produce but if the flow rate is not high enough in the plumbing, it cannot produce the pressure. So even if you redirected all of the flow through the tube, there would still be some flow rate through the tube (~ 5 GPM) and the pressure will be limited to less than 26 PSI. But the turnover rate for the pool would increase to 70 hours!