I heard once this little trick some people with low ppm water can do with there di vessels. Once a chamber has been used with di resin then it'll still purify water quite well if you empty the bad resin and just use it empty. Water round here goes in mine at 156 and comes out at 2. Once your resin is knackered you should try it! It could still knock down your ppm if you have quite bad water in your area. It's saving me a fortune and it's not as heavy to carry round in the van!!! CHA-CHING!!!