Reverse Osmosis Systems

Rainsoft Ultrefiner II 3-Stage RO Conversion Kit Filters

The Rainsoft Ultrefiner II reverse osmosis drinking water system uses expensive proprietary filters that offer few benefits over traditional RO systems, and the filters can only be purchased directly from a Rainsoft authorized dealer.

Alternative Option to Rainsoft Ultrefiner II Filters: To reduce costs, save water, and produce purified water faster, consider converting your Rainsoft system to the PuROTwist Retrofit Kit (PT4000T75-RK). This conversion kit allows you to use PuROTwist filters with your existing Rainsoft faucet, tank, and tubing. Start saving on replacement filters today!

IMPORTANT: The PuROTwist filter kits below only work if you convert your Rainsoft system with the PuROTwist Retrofit Kit (PT4000T75-RK).

RainSoft Ultrefiner II Three-Stage RO System FAQs

What replacement filters fit my RainSoft Ultrefiner II?

Original RainSoft cartridges and PuROTwist cartridges are different. The PuROTwist filters shown here require conversion first.

Can I use PuROTwist filters in my existing RainSoft manifold?

No. Start with the PT4000T75-RK conversion kit.

What does the conversion kit replace, and what can I keep?

It replaces the RO manifold and filters; the PT4000T75-RK conversion kit page says the existing tank, faucet, and lines can remain.

Which filters do I buy after converting?

Choose the replacement kit that matches what you need: a replacement filter kit with a membrane when the RO membrane is due, or a replacement filter kit without a membrane when you are replacing only the routine sediment and carbon filters.

Is this a three-stage or four-stage system?

The original RainSoft Ultrefiner II is a three-stage system. The PT4000T75-RK conversion kit converts it to a four-stage, 75 GPD RO system.

How often do I replace the converted system’s filters?

The PT4000T75-RK kit page lists a 12-month replacement interval for its sediment and carbon filters and 24 months for its RO membrane.

Will conversion save money or water?

Converting may reduce ongoing filter costs and water use, depending on your original RainSoft system, local water conditions, usage, and current replacement filter prices. Compare the cost and specifications of your existing RainSoft filters with the PuROTwist replacement filters before deciding.