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Spa Parts Made Simple

Pumps, heaters, control boards, and replacement parts — without the confusion.

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✔️ Real OEM & compatible spa parts
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✔️ Trusted by spa owners since 2015

Not sure which part fits your spa?

We make it easy to find the right replacement part — without guessing.

  1. Find your spa model
  2. Match the part number
  3. Order with confidence
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SpaShopper makes it easy to find quality hot tub and spa replacement parts without the frustration. From spa pumps and heaters to control boards, jets, filters, and plumbing components, we stock parts that fit a wide range of popular spa brands. Whether you’re fixing a heating issue, replacing a worn pump, or upgrading aging components, SpaShopper helps you get your spa running again quickly and confidently.

Mechanical Thermostats

Mechanical thermostats are adjustable capillary-bulb temperature controls used in older or analog hot tub and spa heaters to regulate water temperature. A probe bulb on a flexible capillary tube senses heater outlet water, and the user-adjustable dial/knob sets the desired temperature (typically 68–104°F range), closing/opening contacts to cycle the heater element on/off—providing simple, reliable non-electronic temperature control without digital sensors or circuit boards.

This category includes replacement mechanical thermostats and compatible options, featuring bulb diameters (1/4", 5/16", 3/16"), capillary lengths (12"–48"), adjustable ranges (e.g., 60–140°F or spa-specific 68–104°F), SPST contacts (25A–30A rating), screw terminals, and mounting brackets/clips. Popular models include Invensys/Robertshaw (e.g., 275- series variants), Watkins/Hot Spring (30210, 30211 equivalents), HydroQuip (34- series), and cross-fits for older Balboa, ACC/CTI, Brett Aqualine, or universal analog heaters. Many are manual dial-adjust with snap-action switches.

Mechanical thermostats vary by bulb size, capillary length, temperature range/scale, contact rating, reset behavior (auto-reset standard), mounting style, and heater/manifold compatibility—precise matching ensures the bulb fits the thermowell/groove, capillary routes without kinking, and the control integrates with the heater circuit.

Common problems include inaccurate temperature (stuck contacts, calibration drift, or scale on bulb), no heat (open contacts or broken capillary), overheating (failed to open or stuck closed), erratic cycling from poor bulb placement, leaks at bulb mount, or corrosion on terminals from humidity/chemistry. Replacing a mechanical thermostat restores accurate, adjustable temperature control in analog systems—often a direct swap with bulb insertion.

To select the right mechanical thermostat:
- Identify your spa brand/model, heater type (analog/mechanical), voltage/amp rating, bulb diameter/capillary length, temperature range (if marked), dial style, and any part numbers (e.g., 275- series, 30210).
- Note symptoms (wrong temp reading, no cycling, visible bulb/capillary damage), or heater markings.
- Avoid guessing—send us clear photos of your existing mechanical thermostat (showing bulb probe, capillary tube length, dial/knob, terminals, mounting, heater well location, and spa label with model/serial number) for expert verification.

**Text or send photos to: 772-800-5445**  
**Or call us at: 844-500-4645**  
We'll confirm compatibility before you order.

SpaShopper is not affiliated with any spa manufacturer. Brand names and part numbers are used for compatibility and identification purposes only.

Shop our mechanical thermostats today to regain precise, dial-adjustable temperature control in your analog spa heater.

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