Hi I have been looking on your website but not sure what I need to purchase. I want to add a extra to pods onto my existing ro unit. I wanted a di and nitrate removal (not sure if the nitrate removal is needed) I wanted these after my ro unit (ro man 50gpd unit)so needed the housing x2 di pod, nitrate removal filter and any fittings to connect the two plus tubing. Could you let me know what I would need please. You can message me if you need any further info.