DIY Error Codes

Pentair MasterTemp gas pool heater Error E01

Water temperature sensor open. The water temperature sensor circuit is open.

Turn the heater off and have a qualified service technician check it, as Pentair's manual directs for E01.

Start the fix →When to call a pro ↓
Full answer & models

Pentair MasterTemp E01 means water temperature sensor open. Turn the heater off and call a qualified technician.

Applies to: MasterTemp 175K (460792, 460793)MasterTemp 200K (460730, 460731, 461000, 461001, 461032)MasterTemp 250K (460732, 460733, 460771, 460772, 460806, 461020)MasterTemp 300K (460734, 460735)MasterTemp 400K (460736, 460737, 460775, 460776, 460805, 461021)
Also searched as: Pentair heater E01, MasterTemp E01, Pentair pool heater E01 error

Gas appliance. Do not keep operating the heater with this code; shut it down and call a technician.
Why
Pentair, what to do if you smell gas: do not try to light any appliance; do not touch any electrical switch and do not use any phone in your building; immediately call your gas supplier from a neighbor's phone. Pentair: this product must be installed and serviced by authorized personnel qualified in pool/spa heater installation; improper installation or operation can create carbon monoxide and flue gases that can cause serious injury or death. Pentair warning: risk of explosion or fire causing burns or death if safety interlocks are disabled. Do not operate the heater when ERR HLS, ERR AFS, ERR IGN, ERR AGS, ERR SFS, E01, E05, E06 or 126 is displayed; shut down the heater ("To turn off gas to appliance", page 43) and have a qualified service technician check the system.

What E01 means

Water temperature sensor open. The water temperature sensor circuit is open.

More detail
Pentair's MasterTemp Installation and User's Guide (Table 8, Heater Error and Fault Codes, page 48) lists E01 as "Open water temperature sensor". The water temperature sensor circuit is open. Pentair: to clear the error, the HEATER OFF button must be pressed.

5-minute checks

Fix it step by step

Step 1 of 2

  1. Shut the heater down

    • 2 min
    • None
    • DIY

    Safety: Gas appliance. Do not keep operating the heater with this code; shut it down and call a technician.

    Pentair: do not keep running the heater with this code.

    More detail

    Shut the heater down.

    Pentair's "To turn off gas to appliance" (page 43): press the OFF button on the operating control and switch off all electric power to the unit. Pentair's remaining steps (removing the access panels to close the gas valve) can be left to your technician.

    Did the code clear?

  2. Call a qualified service company

    • Decision
    • None
    • Pro decision

    Stop here and book a qualified technician.

    More detail

    Call a qualified service company.

    Pentair's manual says only qualified, trained service technicians with appropriate test equipment should service the heater. Pentair lists E01 among the codes where you should not operate the heater and should have a qualified service technician check the system (troubleshooting diagram, page 53).

    Still showing E01?Need a pro → call a pro

Code cleared. Nice work.

Watch the display for a day to make sure it stays clear.

Back to top

Fixed after any step? Watch the display for a day to make sure it stays clear. Still E01 after step 2? call a pro.

Call a pro if…

  • You smell gas (leave first, then call your gas supplier from a neighbor's phone).
  • E01 is displayed and does not clear, or keeps returning.
  • Anything inside the heater cabinet, wiring, or the gas valve.

FAQ

What does E01 mean on a Pentair MasterTemp?

"Open water temperature sensor", per Table 8 of the MasterTemp manual. The water temperature sensor circuit is open.

Source: Pentair MasterTemp Pool and Spa Heater Installation and User's Guide, Table 8 Heater Error and Fault Codes and Troubleshooting, pp. 45, 48 and 53. Written by the DIY Error Codes team. Updated 2026-10-16. DIY Error Codes is independent and not affiliated with or endorsed by Pentair.