Yeah it is Alan , but people on this forum have been telling me that the unger resin is poor so I am ordering Tulsion 115 next. Am also thinking about an RO system mate to be honest , app. this can reduce the reading massively so the water going through the DI vessel will be low to start and therefore last longer.. Another thing mate , One way or another I will be moving on from backpack , poss. a big trolley but hopefully a van system , see how it goes. The backpack is a canny set up but 1st cleans eat up the water and an 18 ltr, pack doesent last long. Even when the first cleans have been done and the work speeds up ( rapidly) carrying around those 25 litre barrels takes its toll , just thought I would let you know, cheers Ted