When you know you live in an area where the nitrate level is high, there are several ways to design a custom purifier under sink or modifying its existing plant. It is best to have at the base, at least, a purifier of 2 levels, with the first filter holder 10 inch cartridge anti sediment 5 micron, then in the second, a charcoal canister for the block bad taste and chlorine. This system alone is sufficient purification of treated water in the Paris region. You can add him an anti cartridge online nitrates of 12 inches, placed horizontally, above the two filter holders. The only drawback is that ending an anti-nitrate cartridge, you may find a slight bad taste to drinking water. It will be necessary to last a charcoal canister 10 inches to find a good quality water. The second solution is to install a purifier of three levels, replacing the cartridge in the middle chabon, the cartridge by anti-nitrate 10-inch container. This avoids the successive additions of cartridges online and reduce the annual cost of cartridges.