Hayward Pool Heater HS Error Code
Quick answer
High Temperature / Rapid Rise High return water temperature or rapid temperature rise detected. Heater starts, runs briefly, then shuts down. Low flow through heater (undersized pump, excessive head, bypass issues), scaled or fouled heat exchanger, variable-speed pump running too slowly during heating. Check that pump is running at adequate speed during heating cycles. Verify bypass valve isn't di
Severity: high · DIY difficulty: intermediate
Safety
TBD - must be written per-code before publish
What HS means
High Temperature / Rapid Rise High return water temperature or rapid temperature rise detected. Heater starts, runs briefly, then shuts down. Low flow through heater (undersized pump, excessive head, bypass issues), scaled or fouled heat exchanger, variable-speed pump running too slowly during heating. Check that pump is running at adequate speed during heating cycles. Verify bypass valve isn't diverting too much flow around heater. Clean or inspect filter. If heat exchanger is heavily scaled, professional descaling may be needed.
Causes, ranked
1. Inlet water temperature above 104°F (resumes 2 min after it drops) common diy-ok
Check:
Fix:
2. Inlet temp rising faster than 6°F/60s while firing - low water flow condition (filter/pump) common diy-ok
Check:
Fix:
3. Faulty inlet water temperature sensor reporting false rapid rise occasional pro-only
Check:
Fix:
Parts & supplies for Hayward Pool Heater: filters, control boards, sensors, and common replacement parts.
Sources
- PoolDial error-code reference (manual-backed) — verified 2026-08-29
- Hayward H-Series H150FD-H500FD Service & Installation Manual (Figure 27: Error codes) — verified 2026-08-29
- PoolDial error-code reference (manual-backed) — verified 2026-08-29