spa parts, hot tub parts and repair help
spa parts, hot tub parts and repair help
spa parts, hot tub parts and service help
spa parts, hot tub parts and repair help
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Thermowell / Drywell Replacement Home

This section demonstrates how a leaking thermowell is replaced on a contractor style spa.  Most older spas utilize a temperature sensor holder like this.  This may or may not be identical to your spa installation, so use this guide with caution, and utilize common sense in determining suitablity for application on your spa or hot tub.
Safety Warnings!
Remove Power from the spa/hot tub BEFORE performing this procedure.  Failure to comply with this requirement, can lead to electrical shock and/or electrocution!

The instructions here are intended for general reference only.  Many hot tubs and spas are different from the one depicted here, and may require more or less mechanical effort or knowledge in order to achieve the desired results.

Here we've got a leak from the inside of a thermo-well, (sometimes referred to as a 'dry-well').  It's basically a hollow tube inserted into the pvc plumbing (usually on the suction side of the plumbing, going to the pump).  In order to repair the problem, the thermostat sensor must carefully be removed, the thermowell removed, replaced, then the thermostat sensor re-inserted into the new thermowell.
On this particular type of thermowell, there is a small cotter pin that must be removed prior to removing the rubber plug and the thermostat sensor.  I use a pair of needle nose pliers to straighten it out and pull the cotter pin through the mounting holes.  Extreme care must be exercised not to damage the small copper capillary tube coming from the thermostat.

With the pin removed, I carefully remove the sensor from the tube.  Note the presence of a lubricant on the sensor.  This is used to more effectively transfer the water temperature from the inside of the metal tube to the sensor itself.  Don't clean this off, it is beneficial to regulating temperature.  In this instance, the lubricant compound has also helped to prevent corrosive damage from the water leak to the capillary assembly.
With the termal sensor removed, all we have to do now is to unscrew the old thermowell from the pvc fitting.  Use care not to stress the pvc piping very much, or you could cause leaks in other parts of the system.  If your thermowell was installed with epoxy sealant, or other kinds of hardening sealant, you may have to break the threaded pvc fitting, in which case you'll have to replumb this assembly with fittings from the local building supply or hardware store.


In almost all cases, removal is easily accomplished by using a pair of pliers, rotating the thermowell counter-clockwise.
Pulling out the old thermowell.  You may have a bit of water come out, but if you're ready for it, the new thermowell can be put in within seconds.

Typical leaking thermowell... with a small hole corroded into the end of it.
This is the replacement thermowell, smaller and less expensive than the original... but it works very well for the application, as long as the thermostat sensor diameter does not exceed the diameter of the well.  In this case, I've lubricated the threads of the plug with water-lube, to ensure a positive seal on the threads.

Installation is very simple.  All I do is screw the new thermowell in place by hand. 
And it's ready to accept the thermal sensor.

Carefully pushing the sensor in as far as it will go....
Now I will carefully dress the capillary tube in a fashion that will keep the sensor in place.  (The previous installation used the cotter pin for this).

Note how I used a simple nylon tie-wrap to hold the sensor in place.  You can use electrical tape or even duct tape to achieve the same results.

Next thing, fill up the spa and check for leaks.

Metro Atlanta Spa/Hot Tub Service
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