Just bought a new/used hot tub, filled and when I turn it on jets come on and everything seems ok then..... error -03 ( water flow problem) it will show the error and turn off pump and heater. It will wait a minute then kick on and shut of 10 seconds later. It will then come on for 10 minutes straight then back to error..... I took out the old filter and ran without filter with no luck. Any ideas?