We've had a Simpson Eziset550 for a couple of years and everything seems to function OK except it does not appear to rinse properly. On darker clothing you can see streaks of washing powder through the fabric. I add OMO top loader powder into the machine before adding the clothing and use it sparingly. There is no restriction in the drain hose as it empties without problem. What can I change to improve performance? Regards, Tony and Chris.