Spa Draining Overnight

Why Your Spa Loses Water When the System Is Off

If your spa drains overnight or slowly loses water when the pool system is off, it typically means the spa is not staying isolated from the pool. This is almost always a valve, actuator, or check valve issue, not a structural leak.

Most causes are simple to identify once you know what to look for.

⭐ 1. Spa Return Check Valve Failure (Most Common)

Your system includes a check valve that prevents spa water from flowing backward into the pool when the pump shuts off.

If this valve fails, sticks open, or cracks, the spa will drain down to the level of the pool.

Signs of check valve failure:

✔ Spa drains to pool level overnight

✔ Water spills into the pool after the system turns off

✔ You hear a “glugging” sound when the pump shuts down

Fix:

• Inspect the check valve lid for cracks
• Check the flapper for damage or debris
• Replace the check valve if worn

This is the #1 cause of spa draining issues.

⭐ 2. Return Valve in Wrong Position

For the spa to stay full, water must stay isolated inside the spa return loop.

If the valve is:

✔ Partially open

✔ Pointed toward POOL instead of SPA

✔ Not aligned with the handle arrow

…spa water will drain back into the pool.

What to check:

• Make sure the return valve fully points to SPA
• Make sure the suction valve fully points to SPA when in spa mode
• Ensure no water is spilling into the pool after the pump stops

Even a small misalignment can cause draining.

⭐ 3. Actuator Not Rotating Correctly

If your valves are automated (Hayward OmniLogic / OmniHub / OmniPL), the actuators rotate to switch between POOL and SPA modes.

If an actuator is:

• Installed backwards
• Stops early
• Has a broken internal gear
• Has loose toggle switches

…the spa may not isolate correctly.

Symptoms:

✔ Spa drains even though automation says “SPA mode”

✔ Actuator moves to the wrong angle

✔ Valve rotates only halfway

✔ Clicking sound from actuator

Fix:

• Check actuator toggle switches:
• • One side is ON1 / ON2
  • Reverse position if valve turns the wrong way
• Inspect valve alignment
• Replace actuator if gears are stripped

⭐ 4. Leak in Spa Return Line (Rare but Possible)

If the spa drains below jet level, a small underground leak on the return side may be present.

Signs:

✔ Spa drains to a consistent level below the jets

✔ Drains whether system is ON or OFF

✔ Bubbles when switching to spa mode

✔ Requires frequent refilling

Fix:

This requires a professional pressure test.

Most of the time, this is less common than a valve or check valve issue.

⭐ 5. Spillway Running Too Long

If your spillway (overflow from spa to pool) runs consistently, the spa may appear to “drain,” but it is simply circulating into the pool.

Check:

• Automation not stuck in “SPA Spillover” mode
• Spillway schedule not set incorrectly
• Return valve not partially open to POOL

If the spillway never turns off, the spa will gradually equalize with the pool.

⭐ 6. Pump Shutoff Causes Backflow

When the pump shuts off:

• Pressure drops
• Water tries to equalize between spa and pool
• If valves/check valve fail, spa drains

This is why correct valve alignment is critical.

⭐ 7. When to Contact Professional Pool Company

Contact us if:

✔ Spa drains completely overnight

✔ Water level drops below jet level

✔ Check valve looks damaged or cloudy

✔ Valves don’t fully rotate

✔ Actuators behave unpredictably

✔ You see water leaking at the equipment pad

We will inspect:

• Suction & return valves
• Actuator alignment
• Check valve condition
• Spa plumbing pressure
• Automation settings
• Hidden leaks (if necessary)

Most spa drainage issues are fixed quickly with a new check valve or actuator adjustment.

⭐ Summary

If your spa drains overnight, the most likely causes are:

1. Failed check valve (most common)
2. Return valve misaligned
3. Actuator not rotating fully
4. Spillway stuck ON
5. Less commonly — return line leak

Most problems are straightforward and not structural.

⭐ Need Help?

If your spa keeps draining, contact Professional Pool Company. We can restore proper valve function and keep your spa isolated and full.

Updated on: 29/11/2025