The standard sizes for the pre-filters are 2.5" in diameter and 9.75" long. The standard size for the membrane is 1.75" in diameter and 11.75" long. Here is a diagram of it:
If your pre-filters and membrane are not standard sizes, you probably have to go back to the dealer who sold it to you and pay high prices for frequent changes. If you want to convert your system so that it will handle our high-quality standard-size filters and membranes, it costs only $175 (plus $10 shipping). This includes 2 new filter housings, a sediment pre-filter, a carbon pre-filter, a membrane housing, a membrane, an automatic shutoff valve, a capillary restrictor tube, and a post-filter. (You can still use your tank and faucet.)
With this new setup, you won't have to change your pre-filters for 3 years -- and you can either buy them from us (current price is $3 and $15, respectively) or from most water and hardware stores. You won't have to change your membrane or post-filter for 6 years -- and you can either buy them from us (current price is $55 and $8, respectively) or from most water and hardware stores.
R.O. systems are like cars. Your cost to have one is not just the initial purchase price, but the cost of maintaining the system over several years. Over time, you will need to replace components of your system. For instance, we recommend that you change your pre-filters every 3 years (although they will normally last longer than this). We also recommend that you change your membrane and post-filter every 6 years. You may also need a new tank in 6 years.
So for the first 6 years, your only expected costs will be the $175 purchase price for the conversion kit plus one sediment filter at $3 and one carbon filter at $15. (This averages out to $2.68 per month.)
For the first 12 years, your only additional major costs should be:
3 sediment filters at $3 each: $9
3 carbon filters at $15 each: $45
1 membrane: $55
1 post-filter: $8
1 tank: $60
If you take the initial purchase price of $175 and add the $177 figure, that totals $352. If you divide that by 12 years, our system will cost you an average of $29.33 per year or $2.44 per month.
So what you should do is figure out how often you will need to change filters, the membrane, and the tank over the next 12 years, figure out the costs of the components, and see how it compares to your costs with our conversion kit.