Grundfos CR vs CRI vs CRN: Which Material Do You Need?

The short answer: choose a CR for clean, non-aggressive water, a CRI when everything the liquid touches must be 304 stainless steel, and a CRN when the liquid is aggressive, contains chlorides, or needs 316 stainless. All three share the same hydraulics, so a CR3-10, a CRI3-10 and a CRN3-10 deliver the same flow and head. The letter changes the metal, not the performance.

That makes the decision simpler than it looks. Size the pump first (flow, head and stage count), then pick the material your liquid calls for. This guide covers what each version is made of, where each one belongs, and what to check before you swap one for another. You can compare every model in the Grundfos pumps collection at ePumps.

CR vs CRI vs CRN at a Glance

1. Grundfos CR: Cast Iron Head, Stainless Internals

The standard CR pairs a cast iron pump head and base with 304 stainless steel impellers, chambers and outer sleeve. The liquid touches cast iron where it enters and leaves the pump and stainless steel everywhere in between. That combination is durable and the most economical of the three, which is why it is the default for municipal pressure boosting, HVAC circulation, glycol loops and boiler feed on treated water.

The weak point is the cast iron. In aggressive water it corrodes, and in high purity water it sheds iron into the liquid. If you see rust inside the pump head or pitting at the base on an old CR, that is the sign to step up. Example: the Grundfos CR3-10.

2. Grundfos CRI: All-304 Stainless Wetted Parts

On a CRI, every part in contact with the liquid is 304 stainless steel. The "I" version removes the cast iron from the liquid path, so there is nothing to rust and nothing to shed iron. That makes it the usual pick for drinking water systems that want no iron contact, reverse osmosis feed, softened or lightly treated water, and light industrial washdown.

CRI covers the smaller frames. ePumps stocks CRI1 through CRI20, which is where most commercial booster and water treatment duty points fall. Example: the Grundfos CRI3-10. For a broader look at the metals, see cast iron vs stainless steel pumps.

3. Grundfos CRN: 316 Stainless for Aggressive Liquids

A CRN is built with 316 stainless steel in every wetted part. The molybdenum in 316 gives it much better resistance to pitting from chlorides than 304, which is the main reason to choose it. Grundfos describes the CRN for systems where all parts in contact with the liquid must be high grade stainless steel: process water, mild chemicals, food and beverage, and high purity lines.

CRN runs into the larger frames as well. In the 32 frame and up, the usual step up from a CR is a CRN. Examples: the Grundfos CRN3-10 and the Grundfos CRN10-1.

Same Curve, Different Metal

Because the hydraulics are shared, the numbers in the model mean the same thing across all three. In a CRN5-13 the 5 is the nominal flow in cubic meters per hour and the 13 is the stage count, exactly as it would be on a CR5-13. Our guide to Grundfos model numbers decodes the rest. An E added to the range (CRE, CRIE, CRNE) means an integrated variable frequency drive; the material rules stay the same. See VFD vs fixed speed if you are weighing that option.

How to Choose: 5 Questions to Answer

1. What exactly are you pumping?

Clean, cold or hot water with normal chemistry is CR territory. Water that must stay iron free points to CRI. Anything corrosive, chemical, or food contact points to CRN. When in doubt, check the liquid against Grundfos's list of pumped liquids for your model.

2. How many chlorides, and how hot?

Chlorides attack stainless steel, and heat makes it worse. Grundfos points chloride-containing water to the CRN, and even then within limits: its liquid list cites up to 500 ppm below 86°F. Brackish water, RO concentrate and seawater usually sit beyond that, so ask about titanium (CRT) or a special build before you order.

3. Does the liquid need to stay pure?

Deionized water and RO permeate are hungry for ions and attack cast iron quickly, picking up iron as they go. Use a CRI at minimum and a CRN for high purity or pharmaceutical lines.

4. What temperature range?

All three share the same standard liquid range of -4°F to 250°F, with hot water versions available on request up to 356°F. Temperature affects your seal choice more than the material. The standard EPDM seal (HQQE) suits water and glycol, while oils need FKM (HQQV).

5. What connections and pressure does the system need?

On the smaller frames (CR1s to CR20), an oval flange connection is rated to 232 psi, while ANSI flange and PJE connections are rated to 362 psi. CRNs use ANSI flanges or PJE (Victaulic) couplings rather than oval flanges, so check the piping before you swap a CR for a CRN.

Which One for Which Job?

Most boiler feed duty lands on a standard CR, and many of the Grundfos pumps ePumps stocks are set up for boiler feed service. For pressure boosting, our guide to what a booster pump is covers the system side.

Replacing an Existing Pump? Check These First

• Match the hydraulics. Keep the same size and stage count (the numbers after the letters) so the new pump hits the same duty point.
• Upgrade the metal if the old one corroded. A CR that rusted out is telling you the water needs a CRI or CRN.
• Check connections and height. Moving from oval flanges to ANSI or PJE can mean new flanges or couplings on the piping.
• Confirm the seal code. The last letters of the full designation (for example HQQE) must suit your liquid.

If you are replacing because of a failure, our Grundfos CR pump troubleshooting guide helps you confirm the cause first, so the new pump does not fail the same way. Deciding between a vertical and horizontal pump instead? See Grundfos CR vs CM.

Final Thoughts

CR, CRI and CRN are the same pump in three metals. Size it first, then let the liquid decide: CR for clean water, CRI when nothing but stainless can touch it, and CRN when chlorides, chemicals or purity demand 316. Getting the material right is what makes a Grundfos multistage pump last for decades instead of years. Compare options in vertical multi-stage pumps or the full Grundfos range.

Frequently Asked Questions

What is the difference between Grundfos CR and CRN?

A CR has a cast iron pump head and base with 304 stainless steel internals. A CRN uses 316 stainless steel for every part that touches the liquid, so it resists chlorides and aggressive liquids far better. The hydraulics are the same, so a CR5-10 and a CRN5-10 deliver the same flow and head.

Is a Grundfos CRI pump all stainless steel?

Every part in contact with the pumped liquid is 304 stainless steel. That removes cast iron from the liquid path, which is why the CRI is used for potable water, RO feed and other water that must stay iron free.

Can I use a Grundfos CR pump for deionized water?

It is not recommended. Deionized water and RO permeate attack cast iron and pick up iron as they go. Use a CRI at minimum, or a CRN for high purity lines.

Are Grundfos CR, CRI and CRN pumps interchangeable?

Hydraulically, yes. The same size and stage count gives the same performance. Physically, check the connections first: CRNs use ANSI flanges or PJE couplings rather than oval flanges, so the piping may need to change.