RO Conversion Kits: Upgrade Your System and Save
Article Summary
An RO conversion kit replaces the filter assembly and filters while letting you keep a compatible tank and faucet that work well. It can be a practical alternative when proprietary filters are costly or hard to find. Start with your existing model in the system-to-kit match below, then compare the kit’s features and future replacement costs.
Keep What Works. Upgrade What You Maintain.
A reverse osmosis retrofit kit is more than a set of replacement cartridges. It gives your existing under-sink setup a new filter assembly or manifold, filters and RO membrane. Your tank and faucet may stay in place if their condition and connections suit the new assembly.
This is especially useful when your current manifold locks you into proprietary filters. After conversion, you buy replacements for the new assembly—you do not put its cartridges into the old manifold.
REPLACE
The Filter Assembly
New manifold or housings, treatment filters and membrane for the selected kit.
REUSE IF SUITABLE
Your Tank and Faucet
Keep serviceable components after checking connections, condition and installation requirements.
Illustrative conversion. The exact parts reused or replaced depend on your current setup and chosen kit.
START HERE · MATCH YOUR EXISTING SYSTEM
Find Your Current RO System. Choose Its Conversion Kit.
Look for your complete model name below. A listed model gives you a direct path to the matching kit.
Have One of These Systems?
- Culligan Aqua-Cleer Advanced
- DuPure International Pure Blue
- RainSoft Ultrefiner II
YOUR CONVERSION KIT
PuROTwist PT4000T75-RK
75 GPD · Quick-change filters
Have One of These Systems?
- Culligan H-5 Aqua-Cleer
- Culligan H-53 Aqua-Cleer
- Culligan H-8 Aqua-Cleer
YOUR CONVERSION KIT
PureValue 5EZ50-RK
50 GPD · 1/4-inch tank-to-faucet line
Keep your working tank and faucet. The conversion replaces the old filter assembly. Check that the retained parts are serviceable and allow room for the new assembly. Contact us if your setup has been modified.
Don’t See Your Model? We Can Help.
Other systems can also be converted. For a conventional-housing design, compare PureValue for a 1/4-inch tank-to-faucet line or Goldline for a 3/8-inch line. For an unlisted model, send us the model name and connection photos so we can confirm the right option.
Help identifying your RO system · Call 1 (877) 377-9876
Monday–Friday, 8 AM–5 PM Central
A CULLIGAN OWNER’S CONVERSION STORY
An Alternative to Hard-to-Find Replacement Filters
“I bought our house with a Culligan RO already installed. When it came time to replace filters I learned they were nearly impossible to find. … When replacement time came instead of buying from Culligan, I bought the ESP water conversion kit. Two days later it came and within an hour I had a new system for less than Culligan replacement filters.”
— Glenn S. · October 2026 · Excerpt
This customer describes their own experience. Costs, savings, delivery and installation time vary by system and circumstances.
Should You Replace Filters, Convert or Buy a New RO System?
| Your Situation | Start Here | Why |
|---|---|---|
| The existing system works well and matching filters are readily available | Replace the specified filters | A conversion may add cost without solving a problem. |
| The filter assembly needs updating, or proprietary replacements are costly or difficult to obtain | Compare a conversion kit | A new assembly can change your future replacement options while retaining suitable tank and faucet components. |
| The tank, faucet and other components also need replacement, or your water needs have changed | Compare complete under-sink RO systems | Price the entire job. A kit alone does not renew components you keep. |
PureValue 5EZ50-RK: Conventional Filters for a 1/4-Inch Line
ECONOMICAL REPLACEMENT OPTIONS
PureValue 5EZ50-RK
A five-stage retrofit assembly rated at up to 50 GPD. The current listing specifies 1/4-inch tubing from tank to faucet.
- Conventional housings with replaceable cartridges.
- Filters and extra tubing included.
- Listed assembly dimensions: 17 × 7 × 19 inches.
- Tank and faucet are not included.
Named system matches: Culligan H-5, H-53 and H-8 Aqua-Cleer setups are identified in ESP’s original conversion guide for this option. The kit specifies a 1/4-inch tank-to-faucet line.
Future replacements: 5EZ50 kit with membrane · 5EZ50 filters without membrane · PureValue system review
Goldline-50-RK: Conventional Filters for a 3/8-Inch Line
STANDARD-HOUSING DESIGN
Goldline-50-RK
A five-stage retrofit assembly rated at up to 50 GPD. The current listing specifies 3/8-inch tubing from tank to faucet.
- Conventional housings with replaceable cartridges.
- Filters and extra tubing included.
- Listed assembly dimensions: 17 × 7 × 19 inches.
- Tank and faucet are not included.
Compare this option when you want conventional cartridge housings and your retained setup uses the specified 3/8-inch tank-to-faucet line. Confirm the remaining connections and service space as well.
Future replacements: Goldline 50 kit with membrane · Goldline 50 filters without membrane
PuROTwist PT4000T75-RK: Quick-Change Filters and Lower Reject Water
TWIST-OFF FILTER CHANGES
PuROTwist PT4000T75-RK
A four-stage assembly rated at up to 75 GPD, with quick-change filters and a listed 1:1 wastewater ratio—about one gallon sent to the drain for each gallon of treated water under rated conditions.
- Twist off a used cartridge and twist on the specified replacement.
- 3/8-inch high-flow tubing to the faucet.
- Listed assembly dimensions: 17 L × 12 W × 4 D inches.
- Kit includes the assembly and filters; retain a suitable tank and faucet.
Replaces the filter assembly in these listed systems: Culligan Aqua-Cleer Advanced, RainSoft Ultrefiner II and DuPure International Pure Blue. Choose by the complete model name; other models from the same brand may use a different setup.
Future replacements: 4000T75 kit with 75 GPD membrane · 4000T75 filters without membrane · PuROTwist 4000 review
How Much Could an RO Conversion Save?
The useful question is how the conversion changes your future ownership costs. Compare current filter and service bills with the replacement schedule and prices for the new assembly.
If several retained components also need replacing, use our under-sink RO system comparison to weigh conversion against a complete replacement.
COMPARE THE TOTAL, NOT JUST THE KIT
| Cost to Compare | Keep Your Current Assembly | Convert to a New Assembly |
|---|---|---|
| Initial cost | Repairs or service needed now | Conversion kit, installation and any parts that cannot be reused |
| Recurring filters | Current cartridges and service charges | Matching cartridges for the new assembly and any service charges |
| Membrane | Current replacement cost and schedule | New assembly’s specified membrane and schedule |
| Water use | Your current system’s reject-water ratio and use | Chosen kit’s documented ratio under its rated conditions |
Estimated recurring savings = current filter and service costs − new filter and service costs. Then weigh those savings against the one-time conversion expense. Savings vary; there is no single annual dollar amount that applies to every household.
Plan Filter Changes After the Conversion
Keep the new assembly’s model and part numbers with your records. Your old RainSoft, Culligan or other proprietary cartridges are no longer the replacements to order for the converted assembly.
The kit links above take you to exact replacement options; you can also browse RO filters and membranes.
START THE REPLACEMENT CYCLE
Complete Kit With Membrane
At the first full replacement, use the matching kit that includes the membrane and all treatment filters.
THE FOLLOWING YEAR
Filters Without the Membrane
Use the matching filter-only kit to avoid buying another membrane that year, then alternate as the service schedule allows.
Use this as a planning cycle, not a guarantee of service life. PureValue and Goldline listings call for filters every 6–12 months and the membrane at 24 months; PuROTwist’s supplied guidance lists annual filters and a two-year membrane interval. Water quality, use and current model maintenance instructions can require earlier service.
A Familiar Kitchen Setup With a New Filter Assembly
A successful conversion keeps everyday use convenient while changing how you maintain the system. Retaining suitable tank and faucet components can make sense—but replace parts that are worn or unsuitable.
Plan ongoing RO maintenance · Understand faucet and drain connections
RO installation is a connection-and-startup job, not just a cartridge change. Use the selected kit’s instructions and a qualified installer when needed. Allow time for leak checks, required flushing and tank fill/discard cycles; a short manifold swap is not the complete startup time.
How to Install an RO Conversion Kit
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Step 1: Confirm the conversion before disconnecting anything
Identify and label the feed, tank, drinking-water and drain lines. Confirm the kit, fittings, required space and components to be retained.
Find your model’s owner’s manual before starting.
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Step 2: Shut off, drain and release pressure
Follow the model instructions before removing the old assembly. Isolate any refrigerator or ice-maker connection as directed.
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Step 3: Mount and connect the new assembly
Connect each line to the correct port using the specified fittings and tubing. Check the drain and air-gap arrangement; do not infer connections from a product photo alone.
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Step 4: Check, flush and document the new system
Restore water as instructed, inspect for leaks and complete all required startup flushing and tank-discard cycles before drinking. Record the new model and future replacement parts.
Get Help Matching Your Existing RO Setup
Have your model number, tubing sizes and clear photos ready. Our team can help compare the conversion options and identify what can be retained.
Monday–Friday, 8 AM–5 PM Central
RO Conversion Kit Frequently Asked Questions
My exact system is listed. Is this the right conversion kit?
Yes—use the corresponding kit identified for your exact model in the compatibility table. The conversion replaces the old filter assembly. Confirm that the tank and faucet you are retaining are serviceable and follow the new kit’s installation instructions. If the setup has been modified, ask our team to check it first.
Is a conversion kit the same as replacement filters?
No. A cartridge kit replaces filters within the existing assembly. A conversion kit replaces the assembly or manifold itself and includes filters for that new design.
Can I reuse my current RO tank and faucet?
Often, if they are in good condition and compatible with the selected kit. Check the connections, tank operation, faucet/drain arrangement and current installation requirements before ordering.
Which kit should I compare for 1/4-inch tubing?
The PureValue 5EZ50-RK listing specifies 1/4-inch tubing from tank to faucet. That is a starting point: confirm the remaining connections and operating requirements for the complete setup.
Which kit should I compare for 3/8-inch tubing?
The Goldline-50-RK specifies a 3/8-inch tank-to-faucet line with conventional housings. PuROTwist PT4000T75-RK uses 3/8-inch faucet tubing with quick-change filters. Compare exact compatibility and the filter style you prefer.
Will PuROTwist cartridges fit my old RainSoft manifold?
Conversion means replacing the old manifold with the PuROTwist assembly. Order cartridges for that new assembly afterward; do not assume they fit directly into the old proprietary manifold.
Does an RO conversion always save money?
Savings depend on the old and new filter costs, service charges, any additional parts and the conversion expense. Compare total costs over the same period.
Can I finish the whole job in 10–15 minutes?
The physical assembly swap and the complete startup are different. Installation time varies with the setup and the work needed. Complete all leak checks, flushing and tank-discard cycles specified by the kit before drinking.
Does the kit keep my old system’s certification or treatment claims?
Do not assume an old system’s certification or claims transfer to a changed configuration. Check the documentation for the new assembly and its exact treatment components, especially when targeting a specific contaminant.
More Help With RO Upgrades and Ownership
Review PuROTwist 4000
Explore the quick-change design and listed 1:1 wastewater ratio.
Review PureValue 5EZ50
Compare a conventional five-stage design and replacement options.
Product details: PureValue 5EZ50-RK · Goldline-50-RK · PuROTwist PT4000T75-RK. Check each current listing and installation instructions before purchase.
By Freeman Linton · Updated November 2, 2026
