Replacement Filters for the Universal 4-Stage RO Reverse Osmosis System
Universal · 4-Stage Reverse Osmosis
Replacement Filters for the Universal 4-Stage RO Reverse Osmosis System
Every filter your system needs — stage by stage — led by the IPW house-brand set that costs less than the OEM parts.
Also sold as: Universal 4 stage · 4 stage RO · 2 prefilter RO
✓ Best value — replace everything at once
IPW Universal 4-Stage Kit
$39.99
5µm sediment + carbon block (both 10" × 2.5") + 50 GPD 1812 membrane + 10" inline GAC with ¼" NPT threads. Fits most 4-stage RO systems with standard housings.
🛒 Add the complete set to cartInline post-filter has push-in tubing ends? Get the ¼" quick-connect version — $42.99.
Filters by stage
Buy the whole set above, or replace stages individually below.
2
Carbon block / GAC
5µm coconut carbon block · 10" × 2.5"
3
RO membrane
50 GPD thin-film composite · standard 1812 size
IPW TW-1812-50 — 50 GPD membrane — $32.99
4
Inline post-carbon polish
10" GAC inline · ¼" female NPT threaded
IPW AICRO — inline post-carbon — $8.00
When to replace
🪣 Sediment & carbon: every 6–12 months🥤 Inline post-filter: every 12 months💧 RO membrane: every 2–3 years
✓ Fits 4-stage RO systems with standard 10" × 2.5" housings and an 1812 membrane — not sure? call (714) 541-6600.
Not sure this is your system? Use the Isopure Water Filter Finder → Match by system name, by the part number printed on your current filter, or by snapping a photo.
Universal 4-Stage RO filter FAQ
Will this kit fit my 4-stage RO system?
It fits 4-stage systems that use standard 10" × 2.5" filter housings, an 1812-size membrane and a 10" inline post-filter. Measure your old cartridges, or send a photo through the Filter Finder.
Do I need the NPT or the quick-connect version?
Look at the ends of your current inline post-filter. If the tubing screws onto threaded fittings, order the ¼" NPT kit. If the tube pushes straight into the filter, order the ¼" quick-connect kit.
What is the difference between a 4-stage and a 5-stage RO?
A 4-stage system has one carbon block before the membrane. A 5-stage system has two. See the universal 5-stage page if you have two carbon housings.
How often should I change the filters?
Replace the sediment and carbon filters every 6 to 12 months and the inline post-filter every 12 months. The membrane usually lasts 2 to 3 years.
All replacement filters by system · Universal 5-Stage RO · Watts W-415 (4-stage) · Watts Premier 560032 (4-stage)
Compatibility reference only. Photos of complete systems shown on this page are provided to help you identify your unit and confirm that our filters fit. All brand names, model numbers, and product images are the property of their respective owners; Isopure Water (IPW Industries Inc.) is not affiliated with, sponsored by, or endorsed by these manufacturers. We sell compatible replacement filters and parts — not the branded systems pictured, unless a system is separately listed for sale on our store.
