Problems with reverse osmosis water treatment system

Hi there ! I had a Maruyama reverse osmosis water filtration system installed in Dec 08 . in the first month it used up one bag of salt i replaced this bag of salt but then forgot to keep checking the bin unit where the salt is stored. They guy who installed it said usual consumption about one bag a month, so when i checked on it next i found that the salt in the bin had almost gone completely and bought a bag that very day. This time i bought the recommended salt lumps instead of ordinary salt cristals which i had used the once in the interim. Now there appears to be no change in the amount of salt lumps in the bin even though the salt had been put in over 5 weeks ago, it seems as though there is no proper activity in the unit. I was wondering if the bin is supposed to be full of water all the time or if the water gets pumped into the bin when it self cleans and then pumped out again. In the bin one can also see where the old level of the water was around the rim. At present there is only tiny bit of water in bottom of bin but i do not know whether when it is in the cleaning process this water level rises?? what can i do to find out if the system still funktions correctly, tried ringing the supplier they seem to have gone out of business as no reply to phone calls mess. etc help would be very much appreciated as i kinda worry about the state of the water from our well in Ireland thanks tina