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Why is My Hot Tub Empty?

A hot tub that is unexpectedly empty can lead to some unexpected expletives. In this article, we will seek to solve the often-asked question of “Why is my hot tub empty?”

The scene: You’ve come home from a long day at work. Since lunchtime you’ve been thinking of how nice it will be to come home and take a nice relaxing dip in the hot tub. But, after putting on your bathing suit and removing the cover, you discover there is no water in your hot tub. If this scenario sounds similar to your current situation, there is likely an issue with your plumbing, backflow check valve, or a stampede of elephants rolled into town and promptly guzzled up your hot tub water. Okay, that last scenario is completely unlikely, but we wanted to keep you on your toes. So, let’s start narrowing down the list of suspects, shall we?

Before you begin to poke around and diagnose your hot tub issue, it’s a good idea to cut power to the unit by flipping the breaker switch. (Nothing ruins an already-bad day quite like being shocked by 220 volts of electricity.)

Suspect #1: Bad Backflow Check Valve or Debris Buildup

If you’ve recently noticed that your pump isn’t creating all those wonderful bubbles like it once did, or your hot tub begins to drain out once you start it up, then the backflow check valve is a likely suspect.

“But, what is a backflow check valve?” That’s a great question, and we’re glad you asked. The backflow check valve keeps water from back-flowing and entering your hot tub’s pump. Like all hot tub components, the backflow check valve can simply wear out, or become clogged with debris. Having a bad check valve can be dangerous as it creates a situation where water enters into the electrically powered pump. But, in all likelihood, if the problem persists, you will simply be stuck replacing the pump.

Backflow check valves come in a few different varieties, the most common being the in-line (self-contained) and three-way (tee fitting) styles.

  1. In-line check valves (standard hot tubs) — Your everyday, run-of-the-mill hot tub will most likely have an in-line backflow check valve connected to the tubing. This is usually located right before the pump. (Some models have an additional check valve after the pump to make it easy for technicians to swap out pumps.) If you don’t see any debris within the check valve itself, there is a simple test you can perform to determine if the unit has gone bad. Remembering the position of how the check valve was positioned, place the valve on your lips and try to blow through both ends. If you are able to push air through both ends of the valve, this is a sign that an inner seal or gasket has gone bad and the check valve should be replaced.
  2. Spring-loaded check valves (in-ground hot tubs) — Most issues with spring-loaded backflow check valves can be remedied with a little purpose-formulated lubrication. Use a plumber’s wrench to twist off the cap of your spring-loaded check valve by turning it in a counter-clockwise motion. Once the cap is off, the check valve can usually be removed by pulling it out of the pipe with your fingertips. Remove any debris and lubricate the rubber seal by applying a moderate amount of lubrication around the edges. Slide the check valve back into place, ensuring the spring is aligned with the cap, then retighten the cap using the plumber’s wrench.
  3. In-line check valves (pool-connected varieties) — Many hot tubs with connected swimming pools use an in-line check valve type of assembly. These usually have a lid secured using a number of machine screws. If you have ordered a replacement, you can either plumb-in the new valve, or simply replace the lid and O-ring assembly (make sure the dimensions of your old and new check valves are identical). If you’ve determined that debris is the cause of the valve malfunction, cleaning out the debris and lubricating the O-ring should take care of the issue.

Suspect #2: Plumbing Leak

If you’ve read our article on how hot tub plumbing works then you’re already familiar with how complex hot tub plumbing systems can be. Yes, a hot tub’s plumbing is complex, but don’t let that deter you from investigating the leak and arriving at a solution. These bits of advice will help you in your search:

  • Check for a bad seal — While PVC pipes can burst if water freezes in the line over the winter, the most likely culprit of your hot tub’s leak is a bad seal. If you’ve examined the check valve (or valves) and determined it is not the cause of your leak, a corroded pump seal may be to blame. If water has puddled below your pump then this is a logical place to start. If the pump is a number of years old, it may be in your best interest to replace your hot tub pump. For newer models, a seal replacement could remedy the issue. Some other components that use seals and gaskets are heaters (assembly manifolds), gate valves, certain types of connections, and pressure switches. If everything checks out in these departments, it’s time to move onto the pipe unions and connections.
  • Check pipes, elbows, unions, connections, and tees — If your hot tub is completely drained it may be difficult to locate a leak within a pipe union or connection. Finding the leak will be easier if you can find an area with mineral buildup or a dripping connection/union. Even if your hot tub was purchased recently, a union can shake loose during shipment or while the hot tub pump is operating. So, as you go about your inspection, it’s a good idea to see if you can hand-tighten these connections. Since these parts are made of PVC, a wrench should never be used to tighten a union. You may even need to realign some of the components by loosening the mounting bolts on the pump and moving everything back into position before you hand-tighten the unions.

Suspect #3: Leaky Jet

Sometimes it’s easy to forget that the jets and nozzles also have their own connections and fittings. If after filling your hot tub you notice that the water only drains to a particular level, examine the jets directly above the water line.

Suspect #4: Cracked Shell

A crack in the shell may be one of the more obvious sources of a leak, but if you’ve examined all other areas of your hot tub, it may be worth your time to examine the shell. Some hard-to-see, hairline cracks can be found by running your fingers around the shell. You should be able to feel a subtle difference once you come upon a crack. While some cracks are simply cosmetic imperfections, others can cause your hot tub to leak over time. With the acrylic shells of modern hot tubs, cracks that lead to leaks are normally not an issue, but it is a more likely scenario than that herd of elephants we mentioned earlier.

Still Can’t Locate Your Hot Tub’s Leak?

If you’ve checked the seals, pipes, and fittings, but still haven’t found the cause of your hot tub leak, you can apply a leak-detection dye (dark food coloring works, too) to your hot tub’s water, then wait for the dye to appear around a seal or fitting.

Final Thoughts

A hot tub that leaks out the same amount of water after each fill is usually indicative of a leak in the jet assembly. You can also narrow your search by determining if your hot tub leaks faster with the pump running or when it is off. Hot tubs that leak quickly with the pump running usually means there is an issue on the pressure side (the lines after the pump), while hot tubs that leak more slowly with the system on usually have an issue on the suction-side of the plumbing (the lines before the pump).

We hope these bits of advice resolved your leak issue and that you are soon enjoying your hot tub once again.