Product Overview

The Pentair 77707-0234 is a genuine OEM cupro-nickel tube sheet coil assembly kit (heat exchanger) for Pentair MasterTemp 400NA natural gas and 400LP propane pool and spa heaters. The heat exchanger is where the burner's heat transfers into the pool water. This kit replaces a coil that is leaking, scaled, corroded or no longer heating efficiently, restoring heat transfer and heater performance without replacing the whole heater. Cupro-nickel tubes resist corrosion better than standard copper in demanding pool water conditions.

⚠️ Important Purchase Notice

This is a major internal heater component. Installation should be done by a qualified pool heater technician following Pentair's service instructions and local codes. This item ships at about 41 lb. Inspect the shipment upon arrival and report damage promptly.

WARNING: This product can expose you to chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65Warnings.ca.gov.

Ideal For

• Replacing a leaking or failed heat exchanger on a MasterTemp 400NA or 400LP heater.
• Heaters with scaled or corroded tubes and reduced heating output.
• Rebuilding an otherwise serviceable 400K MasterTemp heater.
• Pool heater service technicians.

Key Features

• Genuine Pentair OEM part, number 77707-0234.
• Cupro-nickel tube sheet coil assembly for 400K BTU MasterTemp heaters.
• Fits natural gas (400NA) and propane (400LP) models.
• Includes the coil/tubesheet sealing O-ring kit.
• Direct replacement for the factory heat exchanger.

Benefits

• Restores efficient heat transfer and full heating performance.
• Stops water leaks from a failed coil.
• Cupro-nickel construction for longer life in pool water.
• Lower-cost repair than replacing the entire heater.

Compatibility

For Pentair MasterTemp 400NA and 400LP heater water systems. Other BTU sizes and HD models use different heat exchangers. Confirm your heater's model number, serial number and existing part number against the Pentair parts list before ordering.

Installation or Upgrade Context

Turn off power, gas and circulation, let the heater cool and drain it. Remove the manifold and the old tube sheet coil, install the new 77707-0234 with the supplied O-rings, then reassemble. Restore water flow, check for leaks, and test the heater for proper operation and combustion.

What’s Included

• One cupro-nickel tube sheet coil assembly (heat exchanger)
• Coil/tubesheet sealing O-ring kit

Specifications

Warranty

Covered by a 60-day manufacturer warranty, subject to Pentair’s applicable terms. Contact Pentair for warranty claim instructions; Pool Supply Depot can provide proof of purchase.

Customer Q&A

Which heaters does this fit?

Pentair MasterTemp 400NA (natural gas) and 400LP (propane) heaters.

Does it fit the MasterTemp 400 HD?

No. HD models use a different heat exchanger kit. Confirm your model before ordering.

Are O-rings included?

Yes. The coil/tubesheet sealing O-ring kit is included.

Can I install it myself?

Professional installation by a qualified pool heater technician is recommended.