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Pump Union 400-5990 - Bubbles Supply

Pump Union 400-5990

Part #: 400-5990

$21.72
In stock — ships today
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1-year warrantySame-day ship before 3pm CTPerfect Fit Guarantee30-day returns

About this union/fitting

The Waterway Pump Union 400-5990 is a premium plumbing fitting designed for spa and hot tub circulation systems requiring a 2-1/2" FBT x 2" slip connection. This OEM-quality union provides a secure, leak-proof connection between your pump and plumbing lines, ensuring reliable water flow and system performance.

Engineered to Waterway's exacting standards, this union features durable construction that withstands the demanding conditions of spa environments. At Bubbles Supply, we guarantee an exact fit for your system and back every purchase with our comprehensive 1-year warranty. Orders ship same-day for fast repairs that get your spa running smoothly again. Before installation, verify your existing union measurements match the 2-1/2" FBT x 2" slip specifications to ensure proper fitment and optimal seal integrity.

Exact part number

400-5990

Save this for ordering or warranty claims

Also known as / Replaces

This part replaces or is interchangeable with:

  • 2-1/2 inch FBT union
  • 2-inch slip union
  • Pump union fitting
  • Waterway plumbing union

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

Technical specifications

Union size
2-1/2" FBT x 2" slip

Plumbing notes

  • Union size: 2-1/2" FBT x 2" slip

Need help measuring? Email hello@bubblessupply.com with a photo of your existing plumbing.

Common symptoms this part fixes

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

  • Active leak at pump inlet or outlet connection
  • Water seeping from union threads or slip joint
  • Cracked or brittle union body causing slow drip
  • Union nut won't tighten or seal properly
  • Visible stress fractures in existing union fitting

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

Before you buy — quick checklist

  • Measure your existing union — confirm it is a 2-1/2" FBT (female bottom thread) on one side and 2" slip on the other
  • Inspect whether the leak is at the union itself or at the pipe joint — a union swap won't fix a cracked pipe
  • Check that your existing plumbing is 2" pipe to match the slip end
  • Confirm this is a Waterway pump — union thread pitch and dimensions are brand-specific
  • Have a replacement union O-ring or gasket on hand before starting — do not reuse a compressed or deformed O-ring

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

  • Pump union body (400-5990)
  • Union nut
  • Union O-ring or gasket

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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