Overflow, Skimmer and Hidden-Weir Pools Compared

A skimmer pool collects surface water through skimmers, suction openings set into the pool wall. The pump draws water from these and from the main drain, passes it through the filter and sends it back through the return inlets. Because the water level is held at the middle of the skimmer mouth, a visible band of wall remains between the coping and the water. The system needs no balance tank, its plumbing is simpler and its upfront cost is lower. Its weak point is surface cleaning: leaves and dust only drift towards the spots where the skimmers are, so they should be placed with the prevailing wind in mind.

In an overflow pool the water sits level with the edge and spills into a channel around the perimeter. It is also called a deck-level pool. The water drops through a grated channel into a balance tank; the pump takes it from there, runs it through the filter and returns it to the pool. Debris is skimmed off along every edge all the time, so the surface stays cleaner and the pool reads as one plane with the paving. In exchange you need a balance tank, a larger plant room and precise levelling of the edge. The 4×8 metre deck-level villa pool we built in Alaçatı is one example. Pools where water falls over a single, view-facing edge are covered in our infinity pool article.

A hidden-weir pool is an overflow pool whose channel is concealed beneath the coping instead of under a visible grating. The water still sits at edge level, but in most designs it runs into the channel through a narrow gap beside the coping stone, so all you see from outside is stone and water. It works on the same principle as a deck-level pool: channel, balance tank and return line. The difference lies in the look and the detailing. With the channel out of sight, cleaning access has to be planned at the design stage. We used this system when renovating a 4×8 metre pool in Ilıca; the details are in our hidden-weir renovation project.

The summary below compares the three systems under the same headings. Because the cost difference varies by project, it is given as a direction rather than a figure.

Water chemistry is managed by the same rules in all three; what changes is where the mechanical cleaning happens. In a skimmer pool the baskets are emptied often, because a blocked basket cuts the flow. In an overflow pool the channel and gratings replace the basket: leaves and sediment in the channel are cleared regularly and the balance-tank level is monitored. With a hidden weir the channel is not visible, so this check must not be skipped. An overflow surface is more exposed to wind; on very windy days evaporation and water loss can rise, so automatic top-up is common. The full weekly routine is set out in our article on how to maintain a pool.

If you want to keep the budget simple and the pool is small or medium-sized, a skimmer system does the job. If you want the water flush with the deck, a cleaner surface and a wet-deck area, an overflow system is the fit. If you want the same function without a grating and with a quieter look, the hidden weir is the right choice. Changing the system on an existing pool is also possible; in our tundra grey renovation in Çeşme the pool was converted to deck-level overflow. At Seçkin Havuzculuk we make this decision during the site visit, around Çeşme, Alaçatı and İzmir, by looking at the plot and the space available for a plant room. The whole process is described on our pool construction page.