Grundfos CR vs CRI vs CRN — Materials of Construction Compared
Three material codes, one pump family. How to pick between Grundfos CR (cast iron / 304 SS), CRI (all 304 SS) and CRN (all 316L SS) for your water chemistry and budget.
The Grundfos CR family ships in three material variants. Same pump end, same impellers, same curves — but radically different corrosion and contamination resistance. Picking the wrong material costs you either money you didn't need to spend, or pump failure inside 12 months.
Material Spec Comparison
| Feature | CR | CRI | CRN |
|---|---|---|---|
| Pump head | Cast iron | AISI 304 | AISI 316L |
| Pump base | Cast iron | AISI 304 | AISI 316L |
| Chambers | AISI 304 | AISI 304 | AISI 316L |
| Impellers | AISI 304 | AISI 304 | AISI 316L |
| Shaft | AISI 304 | AISI 304 | AISI 316L |
| Chloride limit (ambient) | ~200 ppm | ~200 ppm | ~1,000 ppm+ |
| Chloride limit (140 °F) | ~50 ppm | ~50 ppm | ~500 ppm |
| RO pre-feed (city water) | OK | OK | OK |
| RO concentrate / brackish | No | No | Yes |
| Potable water | Yes (NSF certified) | Yes | Yes |
| Food & beverage | Iron in contact | Yes | Yes (preferred) |
| Pharma USP-PW | No | Sanitary kit | Sanitary kit |
| Relative price (CR=1.0) | 1.0× | ~1.3× | ~1.5–1.7× |
When to Choose Each
Choose CR When…
- Clean municipal water, well water with low chlorides (< 100 ppm), softened water.
- Boiler feed, condensate transfer, cooling tower makeup.
- Irrigation, fire jockey, light industrial.
- Heating systems (closed loops with corrosion inhibitor).
Choose CRI When…
- Demineralized or deionized water (no chlorides but reactive otherwise).
- Food & beverage, light dairy, brewery process water.
- Permeate boosting after RO (low TDS, low chloride).
- Hot oils and condensates where cast iron contact is unacceptable.
Choose CRN When…
- Reverse osmosis brackish-water feed and concentrate (chlorides up to ~10,000 ppm).
- SWRO pretreatment (raw seawater filtration ahead of the RO membranes).
- Potable water for cities mandating 316L on contact (common in EU and ME).
- Chemical process pumping with chlorides, sulfates or organic acids.
- Pharma USP purified water, ultrapure water (UPW) loops, semiconductor.
- Sanitary CIP with caustic and acid wash cycles.
Beyond CRN: For full seawater high-pressure RO (35–82 bar at > 35,000 ppm chlorides), step up to a Grundfos BM booster module in 316L, 904L or duplex stainless — designed specifically for SWRO.
Cost vs Risk Calculus
A wrong-material specification is one of the most common reasons pumps fail prematurely. A few representative cases:
- CR specified on RO reject at 4,000 ppm chlorides: cast iron suction housing pits and weeps within 6–18 months. Replacement plus downtime exceeds the original CRN price premium by 5–10×.
- CR specified on hot deaerator water at 200 °F with intermittent oxygen: stainless internals are fine, cast iron base shows rust on the pumped side within months.
- CRI specified on seawater pretreatment: 304 stainless pits at the welds within weeks. Always step to CRN for any chloride above ~200 ppm.
Quick Decision Rules
- Chlorides > 200 ppm or temperature > 140 °F → CRN, no exceptions.
- Food/beverage or pharma in contact with the pump → CRI or CRN.
- Plain water at moderate temperature → CR is fine and saves 30–40 % of cost.
- RO concentrate, brackish water, or seawater → CRN minimum, BM for high-pressure SWRO.
Get Material Recommendation CR Sizing Guide
Frequently Asked Questions
What is the chloride limit for Grundfos CRI 304 stainless?AISI 304 stainless tolerates approximately 200 ppm chlorides at room temperature in oxygenated water. Above that, switch to a CRN with 316L which handles 1,000 ppm or higher in normal service.
Is CRN food-grade?CRN parts are 316L stainless steel — accepted as food-contact in most jurisdictions. For full FDA/3-A or USP-PW pharma compliance, specify the sanitary kit (electropolished finish, sanitary seal, FDA-grade elastomers).
Why is CR less expensive than CRN?CR uses cast iron for the largest castings (head and base) and 304 stainless for the wetted internals, while CRN uses 316L stainless everywhere — including those large castings. The cast-iron versus 316L material premium is the primary cost difference.
Can I use a CR for reverse osmosis?CR can be used on city-water RO pre-feed (low chloride). For RO concentrate, brackish-water RO, or seawater RO, the CRN is the correct choice — 316L resists pitting and stress-corrosion cracking from chlorides.
What about super duplex or 904L?For severe chloride or hot-acid service beyond CRN, Grundfos offers BM booster modules in 904L or duplex stainless. The standard CR/CRI/CRN range does not extend to those alloys.