The extra only saves the trouble of cleaning the main filter too frequently. The cost of filters, especially the RO membrane (the most expensive component) that removes dissolved impurities would still be there. The advantage of my setup would be to prevent RO membrane from getting clogged too early by sediments.<p>The additional filter would look something like this [1]. It&#x27;s an inline sediment filter with a separate casing. For the rest of the unit, you might still be able to buy a complete kit off ebay e.g. [2] &amp; assemble it yourself [3].<p>[1] <a href="http:&#x2F;&#x2F;www.osmiowater.co.uk&#x2F;media&#x2F;catalog&#x2F;product&#x2F;cache&#x2F;1&#x2F;image&#x2F;9df78eab33525d08d6e5fb8d27136e95&#x2F;i&#x2F;n&#x2F;inline_water_filter_15mm_push_fitting_ezfitpro.jpg" rel="nofollow">http:&#x2F;&#x2F;www.osmiowater.co.uk&#x2F;media&#x2F;catalog&#x2F;product&#x2F;cache&#x2F;1&#x2F;im...</a><p>[2] <a href="http:&#x2F;&#x2F;www.ebay.com&#x2F;itm&#x2F;RO-Zoi-Xi-Pure-Filter-Kit-incl-UV-Bulb-&#x2F;111509569265?hash=item19f67cfef1" rel="nofollow">http:&#x2F;&#x2F;www.ebay.com&#x2F;itm&#x2F;RO-Zoi-Xi-Pure-Filter-Kit-incl-UV-Bu...</a><p>[3] <a href="http:&#x2F;&#x2F;www.watergeneral.com&#x2F;support&#x2F;pdf&#x2F;RD102.pdf" rel="nofollow">http:&#x2F;&#x2F;www.watergeneral.com&#x2F;support&#x2F;pdf&#x2F;RD102.pdf</a>