Saturday, March 24, 2012

Split Nuts?

Need to replace a Pump or Heater union nut? 

Many people have a hard time figuring out how to re-plumb or replace broken pump or heater union nuts.


The heaters flared ends prevent one from taking the nut off of the heater tube. Replacing the whole heater because of a broken nut makes no sense. A split nut is the answer, simply cut/remove the old nut. Clamp either side of the split nut over the heater tube and fasten the screws - new nut! 
How to choose the right size nut?

Heater split nuts come in 3 sizes - 1.5”, 2” & 2.5”
The dimensions of each split nut only refer to the heater tube ID not to any measurement taken from the nut itself or from the OD of the heater tube.
There is some slight variance between companies that make heater split nuts but if one was to measure by the flange (not thread) ID they split nuts should be like this…
  • 1.5” Heater split nut has a flange ID of 1-15/16” thread ID 2-3/8"
  • 2” Heater split nuts have a flange ID of 2-5/16” thread ID 3"
  • 2.5” Heater split nuts have a flange ID of 3-1/16” thread ID 3-5/8"

 Heater Union Split Nut


Usually the reason you'll not be able to remove a solid union nut is the pump tail piece flange prevents removing the nut. 
Until this nut became available the only option was to cut the tail piece off and glue in a new one. With a split nut slide the nut back away from the pump and install the split nut in front. 
Pump union split nuts only come in two sizes, 1.5", 2" & 2.5" 
The dimensions of each split nut only refers to the pump suction or discharge plumbing ID not to any measurements taken from the nut itself or from the OD of pump threads.

  • 1.5” Pump split nut has a flange ID of 2-3/16” thread ID 2.5"
  • 2” Pump split nuts have a flange ID of 2-11/16” thread ID 3"
  • 2.5” Pump split nuts have a flange ID of 3-1/4thread ID 3-5/8"

Pump Union Split Nuts


  1. I cracked my Jacuzzi J325 pump union nut. Is there a split nut for this model?

    1. Hi Ed,
      Do you have the model # for the pump itself? Those spas came with a few different style pumps. A few models have a proprietary union others could use a standard pump split nut. We just need more information to be sure we recommend the correct item

  2. And what about those of us who have a Dynasty Spa with a 4" heater tube? Is there a 4 inch split nut available for us?

    1. The majority of Dynasty Parts are proprietary and can only be purchased through a dealer.
      Do you have the model # of the heater? Maybe there is something we have that could work as an alternative.

  3. I need a heater split nut for a kohler whirlpool tub K-1457. The split nut is 2.5" on the threaded side and opening of the large flange is 1 11/16" (NOT 1 15/16" as listed above).

    1. Thank you for contacting us.
      Kohler bath parts are not standard, they use proprietary parts. I'm afraid none of these standard style split nuts are going to work on that pump.

  4. I have an old 2000 Hot Spot SE. My pump compression nut is leaking. Do I need the 2" nut or 2.5"? I believe it has a Wavemaster 3000 pump.

    1. We would need to see the pump to be sure but the majority of the 3000 jet pumps in that model year used a 1.5" pump union.
      You want to use the 1.5" pump split nut.

  5. This comment has been removed by the author.

  6. This comment has been removed by a blog administrator.