Abstract: A portable swimming pool water level maintenance device for releasible attachment to a swimming pool having a built-in skimmer. The device includes an upright conduit open at each end and having a conventional toilet ball cock valve and vertically slidable float assembly mounted therewithin. The water inlet of the valve is connectable to the water discharge end of a garden hose, fill water being supplied from the garden hose through the valve to raise the water level sufficiently for the float to close the valve. The conduit is held in upright orientation and vertical position by three spaced, parallel elongated horizontal support members and an elongated upright support member connected to the side of the conduit and arranged to releasibly engage against the deck, inside upper surface of the skimmer and the pool wall surface just below the skimmer.