Perimeter overflow spas: collection, operating modes and acceptance checks
A dry spot on one edge wastes the even sheet a perimeter overflow spa is built for. Record whether the rim is flush or raised, and where the spilled water is held, before that edge is formed.
A perimeter overflow spa spills over the whole rim into a slot or trough, and the collected water is filtered and returned. Premier Paradise's gallery splits that rim into two builds: flush with the deck, water entering a thin slot, or raised above the deck. California Pools & Landscape describes a hidden trough or catch basin that catches the spill and sends it back, and notes that the supply can be the pool or a hidden reservoir. Complete the three records below with the designer before the rim height is set: rim type, where the water is held, and what is reviewed with the system off, circulating, occupied, and with jets running. Edge tolerance, vessel volume and pump duty belong on the project drawings.
Is the rim flush with the deck or raised?
Specify flush or raised before the finish is chosen. Premier Paradise's gallery describes a deck-level rim as water entering a thin slot between the spa edge and the deck (which it terms a mirror effect), and a raised rim as water held above the deck (which it terms a floating water effect).
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| Arrangement | What the gallery states | What to write down |
|---|---|---|
| Flush with the deck | Water enters a thin slot between the spa edge and the deck material. The page calls this a mirror effect. | Slot location and the deck material, from the drawing |
| Raised above the deck | The rim sits above the deck. The page calls this a floating water effect. | Lip height above the walking surface, from the drawing |
| Round plan | On a round spa, the same gallery says water spills over the entire circumference. | That the slot or trough follows the whole rim |
Water sent over one side into a swimming pool is a different edge. Use the raised spillover spa checklist for that drawing. This page stays with a rim that spills into a slot or trough.
Takeaway: Name flush or raised on the drawing before the finish is chosen.
Where does the collected water go?
California Pools & Landscape notes that the spill falls into a hidden collection trough or catch basin, is filtered, and is returned to the vessel from either the main pool or a dedicated hidden surge reservoir. Record which supply arrangement and surge capacity the hydraulic drawing specifies.
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| Field | Write this | Why it is on the record |
|---|---|---|
| Catch | Slot, trough, or catch basin, and where it sits | That page treats the trough or catch basin as the place the spill is collected |
| Holding vessel | Pool, hidden reservoir, or the vessel named on the drawing | The page names the pool or a hidden reservoir as the supply. The drawing picks one. |
| Return | Where filtered water re-enters the spa | Farley wrote on 18 May 2016 that return water has to avoid ripples if the surface is meant to stay glassy while that system runs |
| Grate and debris | Who clears the channel, and the interval the designer sets | The reference articles describe an even sheet; establish the channel-cleaning interval in the maintenance plan. |
Mike Farley noted in WaterShapes (18 May 2016) that the finished top edges of a perimeter-overflow spa must be dead level, citing a crew tolerance target of 1/32 inch to maintain even flow without dry spots. Confirm the exact construction tolerance and leveling method on the project drawings.
Takeaway: Name the catch and the holding vessel on the same drawing.
What should be reviewed in each operating mode?
Review four conditions on separate lines. A still rim with the system off does not describe the sheet with circulation on, and a quiet surface with the jets off does not describe the surface with jets running. Farley tied a glassy top, while that system was running and while it was off, to slow even flow and a return that does not throw ripples.
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| Mode | Watch | Leave this off the pass line |
|---|---|---|
| Off | Water level against the edge with circulation stopped | A photograph taken while the pump is running |
| Circulating, unoccupied | Sheet or slot flow around the whole rim, and the path into the catch | A glassy surface. The 18 May 2016 column ties that look to slow even flow and a quiet return on the system he described |
| Occupied | Where water goes when people displace it | Verify bather-displacement surge capacity on the hydraulic schedule |
| Jets running | Whether the sheet stays continuous | A mirror-flat surface; active hydrotherapy jets disturb the water surface |
Common mistake: Using one still-water photograph as the review for the jets.
Takeaway: Write a separate note for off, circulating, occupied and jets.
What does the designer fill in before the rim is formed?
The project's designer or builder completes this coordination schedule prior to forming the spa rim.
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| Line | Who fills it | Done when |
|---|---|---|
| Rim: flush slot or raised lip, and round or not | Designer | The drawing names one arrangement |
| Catch and holding vessel | Designer | The catch is named, and the supply is the pool, a hidden reservoir, or another vessel on the drawing |
| Level method | Designer or builder | The tolerance they will build to is written, with how they will check it |
| Four operating modes | Person who will run the startup | Off, circulating, occupied and jets each have a note and a date |
Takeaway: The sheet is done when each line has a name and a date.
When this record does not apply
Specify edge tolerance, bather-surge volume, reservoir capacity, pump duty, and suction outlet layout on the project engineering drawings under the locally adopted code.
Evaluate jet-mode operation separately from still-water overflow appearance.
For commercial or hospitality installations, verify state and county public-spa surge and turnover requirements.
Where this rim sits in the rest of the spa is covered on In-ground spa design.
Frequently asked questions
What are the disadvantages of an overflow pool?
Perimeter-overflow systems require tight rim-leveling tolerances (such as the 1/32-inch target noted by Farley) and a collection slot or catch basin that must be kept clear of debris; an out-of-level rim produces dry spots, while a restricted trough disrupts return circulation.
Methods and sources
This guide synthesizes three published industry references on perimeter-overflow spa construction and hydraulic layout (reviewed 11 October 2026).
- Premier Paradise, Perimeter Overflow Spa Gallery (reviewed 11 October 2026). Flush slot, raised rim, and full-circumference overflow configurations.
- California Pools & Landscape, Perimeter Overflow Spa (reviewed 11 October 2026). Hidden trough or catch basin, filtration and return, supply from the pool or a hidden reservoir.
- Mike Farley, #23: Perimeter-Overflow Spa, WaterShapes, 18 May 2016 (reviewed 11 October 2026). Level edges, 1/32-inch leveling tolerance target, and low-turbulence return design for maintaining a glassy surface.
Takeaway: Keep Farley's leveling goal attached to the 18 May 2016 column unless the designer writes the same tolerance onto this drawing.