Direct answer
The cover vault is a formed recess at one end of the pool that houses the fabric drum and mechanism. It must be sized from the chosen system's documentation, given a drain connected to real drainage, closed with a serviceable lid, and reached by the drive's power or hydraulic lines - all details that are cast with the structure.
Key takeaways
- The vault is structural concrete, sized from the specific system's documented dimensions, not from a rule of thumb.
- An undrained or hope-drained vault is the most common cover-system defect; pipe its drain to real drainage.
- The lid must carry deck traffic, match the finish, and still come off for service.
- Power or hydraulic routes to the mechanism end are cast-in reservations with the same deadline as the vault.
The vault is formed concrete, cast at the steel stage. Catalog pages can describe the rest of the system; vault errors stay in the structure. This page is the wet-side detail behind the decisions in cover planning.
Sizing: the system decides, not the rule of thumb
The vault houses the drum, the rolled fabric, and the mechanism. Drum diameter grows with the fabric’s width and length, and every manufacturer publishes the resulting vault dimensions for each model. Name the system before the vault is drawn. A generic vault sized by guesswork either wastes structure or receives a cover that does not fit. The width side of this geometry starts at the track lines. See track types. Track spacing sets fabric width, which sizes everything downstream.
Drainage
Vaults collect water constantly: rain, splash-out, and the sheet of water that comes off the fabric at every opening. The usual defect is a formed vault with no piped drain, which becomes a permanent puddle under the mechanism.
The drain has to be drawn, not improvised. Put a drain fitting in the vault floor, piped to the site’s real drainage (daylight, an approved storm connection, or a sump with a pump where gravity cannot run). Deck drainage matters too. The surrounding deck must shed away from the vault and tracks, a coordination point shared with the coping details in the construction hub. Many systems add a cover pump for water sitting on top of the closed fabric. That pump needs a discharge route, which is also a drawing item.
The lid and service access
The lid carries people at the busiest edge of the pool, finishes flush with the surrounding stone, and still has to lift off for service. Those jobs are resolved with structure: bearing angles or frames, lid panels sized for handling, and finish thickness accounted for. Draw the lid with the coping, not after it.
Power and hydraulic reservations
The mechanism end needs either an electrical circuit in conduit or hydraulic hoses from the pad, per the drive comparison in hydraulic vs electric. Both are cast-in routes with the vault’s own deadline, and both end at the vault with enough service slack to work on the equipment. Electrical details belong to a licensed electrician under local code.
Put it on the checklist
Vault dimensions, drain route, lid detail, and the power reservation each have a line in the cover coordination checklist, and all of them belong in the pre-steel drawing review described in covers for new construction. The vault is the least visible part of the system and the most expensive part to change later.
Frequently asked questions
How big does a cover vault need to be?
As big as the chosen system says. Drum diameter grows with fabric width and length, and the mechanism needs clearance and anchor points, so vault dimensions come from the manufacturer's documentation for the actual model. Designing a generic vault and shopping later is how covers end up not fitting.
Where should the vault drain go?
To wherever the site's real drainage goes - a drain line to daylight, a storm connection where allowed, or a sump with a pump where gravity fails. What it must never be is a closed box. Vaults collect rain, splash-out, and cover runoff continuously, and standing water is what ages the equipment sitting above it.
Does the vault lid matter that much?
Yes, because it is the part everyone touches. It must carry foot traffic at the pool edge, sit flush with the surrounding finish, and still lift off for service without machinery. Lid structure, bearing details, and finish compatibility belong on the drawings with the coping.
Sources
- International Swimming Pool and Spa Code — International Code Council Accessed August 27, 2026.
- Standards and codes — Pool & Hot Tub Alliance Accessed August 27, 2026.