Saturday, July 28, 2012

Why does my spa drain

Why does my spa drain?

This article will focus on finding the reason(s) a spa (in a pool with connected spillover spa setup) would drain after the system is turned off and how to fix it. Written by

1 - Incorrect valve position
The most common reason for a spa to drain is because of an incorrect valve position. This also happens to be the easiest to fix.

Since there is no industry standard setup, below is a picture of the most common suction and return pipe setup. Your system may differ but the principals are the same. (Click on any picture to enlarge)

Suction side (directly in front of the pump):
There are usually two moveable valves on the suction side for selecting between pool and spa. Some, however, have another next to that on the pool side for selecting between the skimmer and pool cleaner.

Return side (either immediately coming out of the filter or immediately coming out of the heater if one exists):
There is a valve to select between pool return and spa return on the return side.

A brief note on valve actuators:
The pictures in this example have valves with electronic actuators on them.

Automatic pool controllers use the actuators to move the valves to change between different filtering modes i.e. Spa mode, pool mode, spa fill, and spa drain. Below are a few examples of automatic systems that use actuators.

These actuators are sitting on standard 180 degree valves.
During normal operation, both valve fronts will be pointed to “spa off”, while the handles point to the open side (as seen in the main setup picture at the top).

These valves can be changed manually via a toggle switch either under the actuator or behind it. Automatic controllers cannot detect if these toggle switches are used and will not auto correct the valve position if manually moved. Sometimes, one of these are accidently switched from being bumped, and will need to be manually toggled back.

How the spa would drain if the valves are turned incorrectly:
A few examples of why your spa would drain if the valves were changed are shown below.

Note: Click on any picture to see a larger version. the blue arrows represent water flow after the system is turned off.

A - A split 50/50 water return.
The idea is to return half the water to the pool and the other half to the spa. When the system is off, the weight of water from the spa pushes water back though the spa return pipe and into the pool return pipe, which drains the spa.

B - Full spa return.
This is the most common mistake and very messy for the pool. The idea is to send all of the water from the system to the spa. When the system is turned off, the weight of the water is pushed through the spa return line, backwards though the filter (pushing dirt with it), backwards through the pump, and then out though the pool suction line.

C - A split 50/50 water suction
Even with a working bypass, this will probably drain the spa when on or off.
This will pull half the water from the pool, then the other half from the spa while returning everything to the pool. When the system is off, the weight of the water pushes water though the spa suction, then backwards down the pool suction line.

D - Full spa suction
Again, even with a working bypass, this one will also probably drain the spa regardless of whether it is on or off.
When the system is off, the weight of the water pushes water though the spa suction pipe, through the pump and filter, then out the pool return line.
On most equipment setups, the valves should be set in the “Spa off” position.

2 - A bad check valve
When working correctly, check valves are inline devices that allow water to flow in only one direction. The most common use of these is on a bypass pipe between the pool and spa return lines.

This is done so that when the system is in pool mode (Spa suction/return off), a small amount of water is allowed to flow in to the spa to keep the spa water moving.

There are many different models of swimming pool check valves and below are pictures of a few different variations.

Some have the option to remove the check valve with quick release unions or a few screws; this is helpful if the problem happens to be an object stuck in the flap or simply replacing a broken flap.

Others will need to be cut out from the system and be replaced with new check valves. These units are cheaper than their removable counter parts. I would never install or recommend a check valve that did not have a removable flapper since it is common for a check valve to fail.

3 - A leaking valve
This one is less common but needs to be checked if all of the above has been already been checked and confirmed to be working properly.
There are rubber gaskets inside of each selectable valve. If this seal/gasket fails, water will flow freely from the spa into the pool.
To replace them, the insides of the valves will need to be replaced. These parts are not a universal size, so you will need the exact make/model and pipe size to replace these.

4 -A cracked pipe or plaster
The most difficult to find and costly to fix is a cracked pipe or cracked plaster. In this case, the water leaving the spa will not return to the pool. Instead, the water would be lost underground. There are various companies that can detect underground leaks without unearthing the pipes. One that we have used in the past is “American Leak Detectors.”

(New)5 -A faulty 3 port valve seal
Although unlikely it is possible for water to flow through a closed three-way valve with or without an actuator attached. This happens when the raised rubber seal breaks or becomes deformed, allowing water to flow past a closed seal. On a perfectly working system, when the system is turned off there should be no sounds coming from the pipes.

I have only seen this happen twice and each time was with a Waterway TruSeal 3 port valve.

Below is a picture of a valve that allowed water to pass through even when closed.

The rubber seal around the edge has torn.

The fix is to replace the insides of the valve. Once the screws holding the top are removed, the top plate can be pulled up and off.

A new TruSeal valve is shown below


  1. I agree with you: a leaking valve should be the least of your concerns, but it still needs to be checked regularly. First of all, it can be pretty obvious when leaking. Also, it can be fixed in minutes with the use of a wrench. :)


  2. Much useful information about drained spa. Similar issue I found with my pool and it was solved when I found small hole in the pool valve actuator.

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