Swimming Pool Leak Detection in Moor Park

Symptoms

At a property in HA6, the swimming pool was full and warm at the time of attendance, which limited the scope of immediate works. The primary concern was the auto top-up system, which was suspected to be losing water, along with potential leaks on the pool return pipework and spa circuits.

The scale of the investigation required for swimming pool leak detection at this site became clear once the engineer began working through each system methodically.

Methods Used

The investigation covered four distinct systems: the auto top-up pot and its mains feed, the pool return outlets, and the spa return and suction pipework. Acoustic testing on the auto top-up pot prompted exposure of the surrounding tiled floor, which revealed extremely dense, steel-reinforced concrete with cables running along a steel beam — making excavation slow and controlled.

This exposure uncovered the mains feed to the auto top-up, half-buried in concrete with wet surroundings, and a leak was confirmed at a 20mm elbow once the water supply was reinstated. An endoscope camera used beneath the pot identified a crack approximately two inches long on the internal edge of the pot itself.

The pool return outlets were then pressure tested and failed, with dye testing showing a draw at both outlets — stronger at the deep end. The endoscope revealed elbows transitioning into threaded fittings connected to what appeared to be black MDPE pipework, representing potential weak points.

The spa circuits were tested separately; the returns dropped pressure in line with the pool returns, and tracer gas testing of the spa returns detected gas traces emerging from around the cannon pipe in the filtration room. The findings across all systems illustrate the complexity that swimming pool leak detection presents when pipework runs through reinforced structural concrete.

Investigation Process

1. 1
   Acoustic testing at auto top-up pot

   Acoustic testing was carried out on the auto top-up pot and anomalies were detected, indicating a leak source in that area.

2. 2
   Exposure of tiled floor surround

   The tiled floor around the pot was carefully excavated, revealing extremely dense reinforced concrete, steel bars of varying sizes, and three cables running along a steel beam — all requiring slow, controlled work to avoid damage.

3. 3
   Mains feed to auto top-up located

   During exposure, the mains feed pipe to the auto top-up was found half-buried in the concrete with wet surroundings. Once the water supply was reinstated, a leak was confirmed at a 20mm elbow on this pipe.

4. 4
   Underside of auto top-up pot inspected

   The area was excavated further to allow access beneath the pot. The endoscope camera identified water running from the base of the pot, traced to a crack adjacent to a section of concrete that had adhered to the pot's exterior.

5. 5
   Crack confirmed inside the pot

   An internal inspection of the pot revealed a crack approximately two inches long along the same edge inside the pot, confirming the pot itself as a leak source.

6. 6
   Repairs carried out to mains and pot

   The mains pipe was cut back in the excavated hole, repositioned, and reconnected to the float valve with new fittings, a new O-ring, grab ring, and nut. The crack on the pot was cleaned, sanded, and sealed on both sides with epoxy resin.

7. 7
   Pool return outlets pressure tested

   Both return outlets were pressure tested and failed to hold pressure. Acoustic anomalies were detected at both, with the deep end outlet more pronounced.

8. 8
   Dye testing on pool returns

   Dye testing under static head confirmed a draw into both return outlets, with the deep end showing a stronger draw, consistent with the acoustic findings.

9. 9
   Endoscope inspection of return pipes

   The underwater endoscope was inserted into both return pipes, revealing elbows transitioning into threaded fittings connected to what appeared to be black MDPE pipework — identified as potential weak points at material change locations.

10. 10
    Spa return and suction circuits pressure tested

    The spa returns dropped pressure in line with the pool returns; the spa suction held approximately 0.4 bar slowly. The visible pipe ends in the undercroft suggested similar fitting-junction issues may be present.

11. 11
    Tracer gas testing on spa returns

    Gas was introduced into the spa return circuit and traces were detected emerging from around the cannon pipe in the filtration room, approximately two steps below pool floor level, indicating a leak on that section.

Result & Outcome

Two confirmed leak sources were located and repaired during this visit. The mains feed to the auto top-up was leaking at a 20mm elbow within the concrete surround; the pipe was cut back, repositioned, and reconnected with new fittings. A two-inch crack on the auto top-up pot was identified using the endoscope beneath the pot and confirmed by internal inspection; this was repaired with epoxy resin applied to both sides of the crack.

The pool return outlets failed pressure testing and dye testing showed a draw at both, strongest at the deep end. Endoscope inspection indicated the likely weak points are elbow-to-threaded-fitting junctions where the pipe material changes to what appears to be MDPE. However, with the pool filtration running, no measurable water loss was observed from either the auto top-up or the water meter — suggesting the return leaks may only occur when the filtration system is off and static pressure is present. The leak rate from the returns is currently unknown and may not be significant in normal operation.

The spa returns showed a pressure drop consistent with the pool returns, and tracer gas confirmed a leak point around the cannon pipe in the filtration room. The dense concrete construction — at least 11 inches thick with possible insulation around the pipework — makes further exposure work necessary to fully assess and repair the return and spa circuits. As a swimming pool leak detection case, the findings here are well-documented and give a clear basis for planning the next phase of work.