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Q12DS

1/2" MPT Flow Switch Q12DS

Part #: Q12DS

$85.48
In stock — ships today
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1-year warrantySame-day ship before 3pm CTPerfect Fit Guarantee30-day returns

About this flow switch

The Harwil Q12DS Flow Switch with 1/2" male pipe thread connection is a critical safety sensor designed for hot tubs and spas that require reliable water flow monitoring. This OEM-quality flow switch helps prevent equipment damage by detecting when water flow drops below safe operating levels, protecting your spa's heater and other components from overheating conditions.

Built to Harwil's exacting standards, this flow switch features a durable 1/2" MPT connection that integrates seamlessly into your spa's plumbing system. At Bubbles Supply, we guarantee this is the exact replacement part your spa needs, backed by our comprehensive 1-year warranty and same-day shipping on orders placed before our cutoff time. Professional installation is recommended to ensure proper threading and optimal water flow detection in your spa's circulation system.

Exact part number

Q12DS

Save this for ordering or warranty claims

Also known as / Replaces

This part replaces or is interchangeable with:

  • 1/2 inch MPT flow switch
  • Harwil Q12DS flow switch
  • paddle-style flow switch
  • spa flow sensor

Looking for an older part number? Check our supersession lookup tool

Common symptoms this part fixes

If your spa is showing any of these signs, this part is likely your fix:

  • Heater throwing HH, OH, or ICE fault codes
  • Spa heater not turning on despite adequate water flow
  • Control panel showing persistent flow or pressure error
  • Spa overheating or shutting down intermittently
  • Flow switch contacts stuck open or closed causing nuisance faults
  • Spa circulation pump running but heater refuses to fire

Not sure if this is your problem? Try our diagnostic centre or .

Before you buy — quick checklist

  • Confirm your existing flow switch uses a 1/2" MPT (male pipe thread) connection — do not confuse with FPT or barb fittings
  • Verify the switch is the flow-type (paddle/flapper style) and not a pressure switch — they are not interchangeable
  • Check your spa control board documentation to confirm it accepts the Q12DS signal output
  • Inspect the existing switch location for corrosion, calcium buildup, or cracked housing that may require additional fittings or pipe repair
  • Confirm fault codes on your control panel — HH, OH, and ICE codes are consistent with flow switch failure, but rule out a failed temp sensor first

Reading the checklist now prevents 90% of returns. Worth the 60 seconds.

Install difficulty: Medium — Some experience neededTypically 30–60 minutes

What's in the box

  • Harwil Q12DS flow switch
  • Lead wires

If your order is missing any items listed above, contact hello@bubblessupply.com within 48 hours of delivery.

Warranty

1 year warranty against defects

Covers manufacturing defects. Does not cover improper installation, normal wear, or accidental damage.

Warranty claims: warranty@bubblessupply.com

Perfect Fit Guarantee

Ordered with our help and the part doesn't fit? Contact us before installation. We'll resolve it with an exchange, replacement recommendation, or return approval.

Learn about our Perfect Fit Guarantee →

Shipping

We ship across the US and Canada. US orders ship from our US warehouse to US customers; Canadian orders ship from our Canadian warehouse to Canadian customers — no cross-border shipping, no surprise duties. In-stock orders placed before 3pm CT ship same day. Standard shipping $9.95 flat rate. Free shipping on orders over $200. Express options available at checkout.

Returns

30-day hassle-free returns on unused parts in original packaging. Contact us before returning to receive your RMA number.

Frequently asked questions

Check the Compatibility section above to confirm fitment for your spa brand and model. If your model is not listed, use our fitment selector at /pages/find-my-part or ask our parts AI for a personalized recommendation.

In-stock orders placed before 3pm CT ship the same day. You will receive tracking information by email as soon as your order ships.

We accept returns within 30 days of delivery for unused items in original packaging. Email returns@bubblessupply.com with your order number to start a return. Installed electrical parts cannot be returned for safety reasons.

Yes, all new parts come with a 1-year warranty against manufacturing defects. Warranty does not cover damage from improper installation or normal wear and tear.

Customer reviews

AI Fitment Assistant

Tell us your spa model and we will confirm this part fits before you buy.

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