SPA Water Level / Water Fall

[MPH]

I have a built in pool which has a spa attached that waterfalls into the pool when the filter is running. The filter is running normally but the waterfall is hardly a trickle. When the filter shuts off the spa drains about 4 inches of water overnight. The valves on the spa are automatic and turning both on and off.

Any ideas ?

[TSH Tech]

Well, the description is vague, no idea what your plumbing setup is, spa elevation above the pool or if it's level, whether or not the filter pad is higher, lower, or level to the spa.
But, this is a common problem when spas empty out after the filter shuts off. First common problem is a bad check valve, followed by bad o-rings or seals inside the valves, followed by bad pump lid 0-ring. Then it gets down to the nitty gritty:
- bad union seals
- bad chlorinator seals or O-ring lid
- bad Frog system O-ring (if applicable)
- bad automatic cleaner thread hose seals(if applicable)
- bad pop-up cleaner seals/ o-rings (if installed)
- bad or weak teflon seal at any threaded point in the plumbing
- worst case, a cracked or broken pipe.

sounds like fun, eh? Somewhere, the weight of the water in the spa is constantly pushing down to wherever the plumbing leads and it found an escape. The first line of defense to hold that water back is typically a check valve, which is why I list it as one of the first problems in the list.