Pool piping covers more than pipes. It encompasses the complete network of fittings, elbows, tees, couplings and valves that connect every component of the hydraulic circuit—from the main drain to the return inlets, from the pump to the filter, from the balancing tank to the pool floor. Each element is sized, positioned and connected according to the hydraulic plan. Together, they determine how water moves through the system.
Why piping decisions cannot wait
The hydraulic plan defines what the network must achieve – flow rates, pressure at each outlet, and circuit balance. The piping translates that plan into physical reality. Once the concrete is poured, every pipe, junction and fitting is sealed into the structure permanently. There is no access, no adjustment, no correction. This is why piping decisions belong at the design stage, not on site.
Pipe diameter – the first critical variable
Diameter determines flow velocity and pressure loss across the entire network. An undersized pipe creates excessive resistance – the pump works harder, flow at the outlets is reduced, and hydraulic balance across the circuit becomes impossible to maintain. An oversized pipe reduces velocity to the point where suspended particles settle rather than circulate.
For each branch of the network – main supply lines, return inlet feeds, and drain connections – the diameter is calculated against the flow rate required and the length of the run. There is no standard diameter that applies across all pools. Every network is specific to its basin geometry, pump specification and filtration capacity.
Pipe routing – how the layout defines hydraulic balance
A hydraulic network functions correctly only when pressure losses are equal across every branch. If one return inlet receives more flow than another, circulation becomes uneven – dead zones develop, chemical distribution becomes inconsistent, and the overflow edge may show surface disturbance.
This means calculating run lengths, accounting for every elbow and fitting, and adjusting diameters where necessary to distribute flow evenly across the circuit. The layout is drawn into the technical documentation before any pipe is laid, not improvised during construction.
In an overflow pool, the balancing tank feed and return circuit adds another layer of complexity. The pipe connecting the tank to the pump and the pump to the pool floor returns must be sized and routed as part of the same hydraulic calculation – not treated as a separate installation.
Materials – what goes where and why
Rigid PVC is the standard for all pipework embedded in concrete – main lines, floor return feeds, drain connections, and any run cast into the pool structure or surrounding slab. It withstands sustained pressure, maintains its geometry over time, and is compatible with all standard fittings. Its rigidity requires precise planning – changes of direction require calculated elbows and fittings, not field adjustments. Rigid PVC is also the material of reference in the technical room, where accessible connections and pressure resistance are both required.
Reinforced flexible PVC – a spiral-reinforced pipe available in rolls of 25 to 50 metres – is used for buried runs between the pool structure and the technical room. Its flexibility eliminates the need for elbows and reduces the number of joints in the circuit, lowering pressure losses across longer runs. It resists ground movement and is compatible with standard PVC fittings and adhesives.
In an overflow pool, HDPE pipe is not part of the specification. The complete network – from the balancing tank through the pump, filter and return circuit – is built in rigid or reinforced flexible PVC, each in its correct location.
Pressure testing – before the concrete, not after
Every pipe run must be pressure-tested before it is sealed into the structure. A leak discovered after concreting is not a maintenance issue – it is a structural problem requiring demolition to access. Pressure testing at the correct stage is not optional; it is the last point at which errors in the network can be corrected without consequence.
The test is carried out on the complete network, under sustained pressure, with all connections made. Any drop in pressure identifies a fault that must be resolved before the pour proceeds.
Diameter, route, material and the pressure test are fixed before the concrete is poured. After that, the network does not move.
Morana’s advice
The pipe is chosen for where it sits.
Rigid PVC in the concrete and in the plant room. Flexible PVC in the buried run to the plant room. Not HDPE.
Frequently asked questions: pool piping
What type of pipe is used in an overflow pool?
Two types of PVC. Rigid PVC for everything set in concrete: main lines, floor returns, drains, and the plant room. Reinforced flexible PVC for the buried run between the pool and the plant room. It follows the trench without elbows. HDPE is not used.
Why does pipe diameter affect pool performance?
Diameter sets speed and pressure loss. Too small, the pump works harder and the returns lose flow. Too large, the water slows and particles settle. Each branch is sized for its flow, its length and its fittings.
When must pool pipework be pressure tested?
Before it is sealed in the concrete. After the pour, a leak means breaking the slab. The whole network is tested under pressure, with every joint in place.
