Water softener resin replacement: standard 8% crosslink vs. ResinTech's highly crosslinked CNS10, how many cubic feet, and what each maker actually publishes
Refill 1 cu ft of 8% crosslink cation resin per rated cubic foot (ResinTech CG8, Purolite C100E). ResinTech's highly crosslinked CNS10 only behind a chlorine feed.
- Verified
- Updated
- 7 min read
- 7 sources
Shop links on this page are affiliate links: a purchase may earn us a commission at no extra cost to you. Disclosure
OwnerSpec compares published manufacturer specifications, certification listings and sourced technical documents. Unless a page explicitly states otherwise, OwnerSpec has not laboratory-tested or used the products it compares. Editorial policy
Short answer
Water softener resin replacement comes down to one grade and one volume. The standard refill is 8% crosslink strong-acid cation resin in the sodium form: ResinTech’s CG8 data sheet states the 8% figure outright and sells it in a 1 cu ft bag, and Purolite’s C100E data sheet lists a 1 cu ft sack as its typical packaging, so one bag fills one rated cubic foot of tank. Both makers put shipping weight at about 50 to 52 lb per cubic foot. Step up to ResinTech’s highly crosslinked CNS10 only if a chlorine or chloramine feed runs continuously ahead of the softener: the CNS10 sheet calls it particularly resistant to oxidation by chlorine or chloramines, sold in the same 1 cu ft bag, and neither 8% sheet prints a chlorine tolerance number. Loose resin is not matched to the valve brand. The spec that must match is the tank’s rated cubic feet, which the resin volume calculator on this site reads off the tank size.
Fact sheet
- Answer
- Refill a softener with 1 cu ft of 8% crosslink strong-acid cation resin per rated cubic foot of tank: ResinTech’s CG8 sheet states the 8% figure and sells a 1 cu ft bag, and Purolite’s C100E sheet lists a 1 cu ft sack at 50 to 52.5 lb. Choose ResinTech’s highly crosslinked CNS10 only when a chlorine or chloramine feed runs ahead of the softener.
- Applies to
- any standard mineral tank sized in cubic feet (Fleck, Clack, Autotrol or Water Right valve)
- Feed: municipal or lightly chlorinated water, or a continuous chlorine feed
- Compatibility basis
- ResinTech CG8 and CNS10 product data sheets, Purolite C100E product page and data sheet, and Purolite’s C100 sodium-cycle engineering bulletin, read 2026-09-13
- Assumptions
- Loose cation resin is not valve-specific: bed volume is set by the tank’s rated cubic feet, not by the control valve brand
- Certifications are as stated on each maker’s own sheet; the NSF and WQA listing databases were not reachable this session
- No maker publishes a gravel underbed volume or a tank-size-to-cubic-feet table that could be read this session, so neither number appears on this page
- Method
- Grades, crosslink percentages, capacities, bag sizes and certifications were copied from the makers’ published data sheets and compared; the capacity-versus-salt figures are readings from the makers’ printed graphs, rounded to the nearest kilograin. Nothing was tested.
- Primary source
- ResinTech, CG8 Product Data Sheet (PDF) (manufacturer or vendor document)
- Facts verified
- Last updated
- Canonical URL
- https://ownerspec.com/water/parts/water-softener-resin-replacement-crosslink-and-how-much/
- Cite as
- OwnerSpec, "Water softener resin replacement: standard 8% crosslink vs. ResinTech's highly crosslinked CNS10, how many cubic feet, and what each maker actually publishes", https://ownerspec.com/water/parts/water-softener-resin-replacement-crosslink-and-how-much/, facts verified 13 September 2026.
Every figure above also appears, with its source, in the page below. All sources · How OwnerSpec verifies numbers
The picks
Live 8% crosslink refill, sold by the half cubic foot
8% crosslink cation resin, 1/2 cu ft
8% crosslink, 1/2 cubic foot bag, per its Amazon listing title
Do not order resin until you know the tank’s rated cubic feet: the grade question takes two sentences, the volume question decides how many bags.
Which resin fits a standard softener tank?
Any grade below fits any mineral tank sized in cubic feet under a Fleck, Clack, Autotrol or Water Right valve, because bed volume is set by the tank, not the valve. The figures are the makers’ published data sheet values, read 2026-09-13; nothing was tested.
| Grade | Crosslink | Capacity (maker’s figure) | Bag | Shipping weight | Certifications (per the maker’s page) |
|---|---|---|---|---|---|
| ResinTech CG8 | 8%, stated on the sheet | 2.00 meq/mL | 1 cu ft | 50 to 52 lb/cu ft | Meets NSF/ANSI/CAN 44, 61, 372 |
| Purolite C100E | Not published by Purolite | 1.9 eq/L (41.5 Kgr/ft³) | 1 ft³ sack | 50.0 to 52.5 lb/ft³ | WQA certified to NSF/ANSI 61 |
| ResinTech CNS10 | Not a published percentage; the sheet calls it a “highly crosslinked gel” | 2.10 meq/mL | 1 cu ft | Not published | Meets NSF/ANSI/CAN 44, 61, 372 |
Crosslink is the percentage of divinylbenzene that ties each bead together, the spec that separates a standard refill from a chlorine-resistant one. Purolite prints no crosslink percentage for C100E, so this page does not attribute 8% to it; its C100 bulletin says only that the family resists oxidizers such as chlorine.
A live Amazon listing, High Capacity Replacement Water Softener Resin , is sold as 8 percent crosslink per its listing title in a 1/2 cubic foot bag.
What else fits the same tank?
The cross-fit question for loose resin is not brand to brand: it is whether the feed carries a disinfectant, and whether the product has a data sheet.
| Alternative | Same volume? | What differs |
|---|---|---|
| ResinTech CNS10 in place of CG8 | Yes, 1 cu ft bag for 1 cu ft bag | ResinTech’s sheet calls CNS10 “particularly resistant to oxidation by chlorine or chloramines”; the CG8 sheet claims only general oxidative stability. ResinTech’s own copy for CNS10 says durability supersedes efficiency |
| Purolite “C-100E-10” | Does not exist as a live grade | Purolite’s C100 bulletin lists six sodium-cycle grades (C100, C100C, PFC100, PPC100, C100DL, C100S) and none is a 10% crosslink gel. Do not order it by that name |
| AFWFilters SOFRES1, “Aquatrol” 8% resin | Not evaluated | Neither maker’s data sheet could be read this session, so no crosslink, capacity or certification figure is printed here for either |
A well with a chlorine or chloramine injection pump ahead of the softener is the case for CNS10.
City water carries at most EPA’s Maximum Residual Disinfectant Level of 4.0 mg/L as Cl2, and neither maker publishes a tolerance figure for 8% resin at that level, so choosing CNS10 there is a judgment call, not a spec match. The chlorine and chloramine guide covers the carbon stage that removes the question.
How much resin does the tank take?
One bag per rated cubic foot. “Bags per cubic foot” is not a real conversion: ResinTech’s CG8 and CNS10 sheets and Purolite’s C100E sheet each list the 1 cu ft bag as the unit, so a 1.5 cu ft tank takes one and a half bags.
The rated cubic feet is on the softener’s spec sheet or read off the tank size: the resin volume calculator carries the standard loading per tank, and the softener size calculator says whether that volume was ever enough.
No tank or resin maker read this session publishes a gravel underbed volume by tank size, so this page prints none: replace the old bed’s gravel to the same depth.
How many grains does each cubic foot deliver at each salt dose?
Capacity per cubic foot depends on the salt dose per regeneration, and the makers publish it as a graph. The readings below are from those graphs to the nearest kilograin (1 Kgr = 1,000 grains) and are approximate; Purolite’s 41.5 Kgr/ft³ above is the chemical maximum, not an operating figure.
| Salt dose (lb NaCl per cu ft) | ResinTech CG8 (Kgr/ft³, from its softening capacity graph) | Purolite C100 family (Kgr/ft³, from the bulletin’s base capacity graph) |
|---|---|---|
| 5 | about 20 | Not plotted at 5 |
| 6 | Not plotted at 6 | about 25 |
| 10 | about 27 | Not plotted at 10 |
| 15 | about 31 | about 33 |
| 20 | about 33, near the plateau | Not plotted at 20 |
ResinTech’s CNS10 sheet has no capacity-versus-salt graph, so the highly crosslinked grade has no maker-sourced grains-per-pound figure. The salt usage calculator turns a dose and a volume into pounds per month.
Who should not do this themselves?
- Anyone without the tank’s rated cubic feet: a guessed volume is the one mistake a bag cannot undo.
- Well owners with iron above ResinTech’s CG8 limit of 1 mg/L of iron per 17 mg/L of hardness: the iron guide puts an oxidizing filter ahead of the softener first.
- Owners of a softener that has stopped using salt: that is usually a salt bridge or a valve fault, not spent resin, so the salt-bridge guide comes first.
- Anyone who cannot lift a 50 lb bag or pull the valve head: the Fleck 5600SXT parts page names the seals and riser that get disturbed, and a dealer rebed is the alternative.
Before you order a bag
Neither ResinTech CG8, Purolite C100E, nor ResinTech CNS10 has a brand-named Amazon listing that could be confirmed this session; the generic 8% crosslink refill above is the one live listing found, and it carries no maker data sheet of its own.
Buy the grade by its data sheet from a water treatment distributor, count the bags off the tank’s rated cubic feet, and choose CNS10 only if a chlorine feed sits ahead of the tank.
Frequently asked questions
What is the difference between 8% crosslink and highly crosslinked water softener resin?
Crosslink is the share of divinylbenzene tying the resin bead together, and a higher share buys oxidant resistance. ResinTech's CG8 data sheet states an 8% crosslink figure, while its CNS10 sheet describes a highly crosslinked gel without a percentage, and calls it particularly resistant to oxidation by chlorine or chloramines. ResinTech's own copy adds that with CNS10, durability supersedes efficiency.
Is water softener resin sold by the cubic foot?
Yes. ResinTech's CG8 and CNS10 data sheets both list a 1 cu ft bag as the packaging, and Purolite's C100E data sheet lists a 1 cubic foot sack as typical packaging alongside 25 L sacks, 5 cubic foot fiber drums and supersacks. So one bag fills one rated cubic foot of tank, and a 1.5 cubic foot softener takes one and a half bags, not two.
What is the EPA limit for chlorine in drinking water?
EPA's National Primary Drinking Water Regulations set a Maximum Residual Disinfectant Level for chlorine of 4.0 mg/L measured as Cl2. That is the ceiling a public supply may carry at the tap, and it is the number to compare against when deciding whether a softener on city water needs ResinTech's highly crosslinked chlorine-resistant CNS10 or the standard 8% grade.
Is Purolite C100E certified for potable water use?
Purolite's C100E product page states the resin is certified by the WQA to the NSF/ANSI 61 standard, which covers the materials in contact with drinking water. That is the maker's own statement; the WQA and NSF listing databases could not be reached this session. ResinTech's CG8 and CNS10 sheets state the resins meet NSF/ANSI/CAN 44, 61 and 372, again per the maker's page.
Can water softener resin also remove iron?
Some, with a stated ceiling. ResinTech's CG8 data sheet says the resin has good capacity for ferrous iron but that iron in the feedwater should not exceed 1 mg/L of iron per 17 mg/L of hardness. Above that ratio the iron guide on this site covers the oxidizing filter that belongs ahead of the softener, and the resin should not be asked to carry the iron alone.
Sources
- ResinTech, CG8 Product Data Sheet (PDF) (manufacturer or vendor document)
- ResinTech, CNS10 Product Data Sheet (PDF) (manufacturer or vendor document)
- ResinTech, media and product listing (strong acid cation resins) (manufacturer or vendor document)
- Purolite, C100E product page (manufacturer or vendor document)
- Purolite, C100E Product Data Sheet (PDF) (manufacturer or vendor document)
- Purolite, C100 Sodium Cycle engineering bulletin (PDF) (manufacturer or vendor document)
- EPA, National Primary Drinking Water Regulations (chlorine MRDL) (government or regulatory source)