SPA Fountain

What it is

The sphere is a welded stainless steel shell — twelve tapered panels and two spun caps, pressed to a true one-metre radius, joined edge to edge, then ground and polished until the seams cannot be found. The finish is a mirror. Standing in a courtyard it holds the whole sky, the planting and the people around it, and the water moving over it makes that reflection breathe.

It sits directly on the paving. The support, the anchorage, the pipework, the reservoir and the whole of the plant are below ground and out of sight. What a guest sees is a sphere, a ring of pebbles, and a four-millimetre shadow gap where the steel meets the stone.

How the water moves

One litre a second — about the flow of a household tap — makes the entire effect. It is the same water all day: the fountain circulates, it does not consume.

1. The pump. A submersible stainless pump sits in a buried reservoir a few metres away and pushes water along a buried stainless line to the foot of the sphere.
2. The riser. The line turns upward and becomes a single 80 mm stainless pipe running up the exact centre of the sphere, inside it, invisible.
3. The conditioner. Just below the top, the water passes through a honeycomb cartridge that removes the swirl the pump and the bend put into it. Water that is still spinning will not lie flat.
4. The crown. It leaves through a 90 mm opening machined flush with the mirror — a weir, not a nozzle. The water domes about 17 mm above the crown and falls back onto the sphere.
5. The sheet. It spreads and thins as it goes: a continuous, transparent film about 0.344 mm thick, taking 5.4 seconds to travel from the crown to the widest point.
6. The break. A little past the widest point the sheet can no longer hold together as one surface. It gathers into fine rivulets that run down the underside, bead, and drip.
7. The catch. Everything lands inside a one-metre radius, on a bed of washed pebble carried on removable stainless trays over a buried collection chamber.
8. The return. A 110 mm gravity drain falls at 1:60 back to the reservoir and the loop closes. A separate filtration circuit runs continuously alongside it.

Why the water looks like glass

The whole effect rests on one number. The film is 0.344 mm thick at the widest point of the sphere and moves at 0.46 m/s. That is thin enough to be optically clear — you see the mirror through it, not the water — and fast enough to stay one connected sheet.

There is a band, and it is narrower than it sounds. Push more water over and the sheet becomes heavier than surface tension can hold to the curve; it lifts away below the equator and turns into a curtain of falling drops — noisy, wind-blown, no longer glass. Send less and the sheet cannot cover the whole circumference; it retreats into separate rivulets with dry mirror between them. The design sits at 1.0 L/s, with good behaviour held from 0.85 to 1.2 L/s, and the pump is speed-controlled to hold that flow rather than a pressure.

The last line is the safety margin. It weighs the water's own momentum against the surface tension holding it to the steel; below 2 the sheet clings, and the design runs at about half that. That margin is what lets the fountain keep working on a warm, breezy afternoon rather than only on a still morning.

Below about 91° from the top the sheet reorganises itself. That is not a fault and it cannot be designed away — it is simply what a falling film does once gravity turns it under the curve. It is also the part people like most: the glass upper half, then a fringe of bright rivulets and beads that catch the light, then the quiet of the pebbles.

The mark

The coral emblem is engraved directly into the mirror, 300 mm across, on one panel face, its centre 1112 mm above the paving — close to eye height for someone standing at the sphere. It sits well inside the glassy part of the film, so the water passes over it as a clear sheet and the mark is read through moving water.

It is engraved 0.020 mm deep — a fiftieth of the thickness of the water above it. That number is set by the film, not by the laser. A mark much deeper than about a tenth of the film thickness raises a visible ridge in the water, and any real step makes the sheet part at its leading edge and print a dry stripe that runs all the way down to the pebbles and never heals. At 0.020 mm the film does not register that the mark is there.

It is marked with a laser that tracks the curve. Across a 300 mm field the sphere falls away by 11 mm — far more than a flat-field marking head can hold in focus, which would burn the middle and fade the edges. The same vector file drives the laser as drew the drawing.

How it goes together

Twenty-six different fabricated parts, every one modelled as a solid before it was drawn. The sphere is welded and polished as one piece in the shop and arrives finished; everything below the paving is set before it comes.

The sphere rests on a 600 mm stainless skirt welded to its underside and bolted to a levelling flange. Below that, a ring cast into the concrete carries six anchor studs and two locating dowels: the flange drops over the dowels, three jacking screws bring the crown level to within a millimetre, and epoxy grout fills the gap. None of that is visible afterwards — the pebble trays cover the whole chamber and lift out by hand whenever anyone needs to get back in.

Every part

Each part below is a solid model, and each mass is measured from that solid rather than estimated. Total fabricated steel is about 1,105 kg; the sphere as installed and drained weighs 695 kg.

What it is made of

Three stainless steels, chosen by where each part has to live. Nothing carbon, nothing plated, nothing sacrificial — in a warm marine atmosphere with chlorinated water those fail quietly, and then all at once.

The mirror is a No. 8 finish, polished after welding so the seams disappear, then passivated. A sample panel is prepared and approved before the sphere itself is polished, so everyone is agreeing about the same surface.

Plant and equipment

The plant is deliberately ordinary — pool-industry equipment, serviceable in the Maldives, with parts available locally. Each machine below was selected against its manufacturer's own published performance curve at this duty, not from a catalogue description.

The reservoir below ground holds 2.6 m³. Water is dosed, filtered and passed through ultraviolet continuously, so what runs over the sphere stays clear and stays sanitary between visits.

Water and power

The sphere recirculates, so the only water it truly uses is what evaporates and what is deliberately let go to stop the salts concentrating.

146 litres a day is roughly one long shower. The 150 W is about two old light bulbs running continuously — this is a low-head fountain, and lifting one litre a second by two metres genuinely costs very little.

In strong wind the control system reduces the flow and then stops it, so water is not thrown across the paving; it restarts by itself when the wind drops. Designed life is fifty years.

Living with it

Everything that will ever need attention was placed so it can be reached without lifting the sphere or breaking any paving.

Two telltales drain into the chamber where anyone servicing the fountain will see them, and a leak sensor reports to the control panel, so the sealed interior cannot fill unnoticed.

Drawings

Twenty-five sheets, issued for fabrication. Every one is drawn from the same geometry file as the 3-D models on this page, so the drawings, the solids and the cutting files cannot disagree with each other. Click any sheet for the full-size PDF.