The plant room: the item most often underestimated

In almost every pool budget that comes to us for review, the plant room appears as a line of builder’s work: so many metres of wall, a slab, a door. And that is how it gets underestimated, because the plant room is not a room. It is where the machine lives that makes a pool a pool and not a large puddle.

There is a reason it was treated so lightly for so long, and it is that until a few months ago no Colombian rule said anything about it at all. That has changed, and it changed recently.

What it is called, and why the name matters

Three names for the same thing, and all three are in use: the trade says cuarto de máquinas, plant room; the statute says casa de máquinas, plant house; and the new resolution says cuarto de equipos, equipment room. This is not pedantry: the word your contract uses decides what you are asking for.

And there is a legal detail almost nobody uses to their advantage. When Ley 1209 defines what a pool is, it does not define the hole with water in it:

The plant house has been part of the pool since 2008, by legal definition. It is not an annexe, it is not ancillary work and it is not an optional item. A pool construction contract that leaves it out is leaving out part of what the law calls a pool, and it is worth saying so in those terms when it turns up as an "extra" halfway through the job.

The decision you cannot undo: the level

Before discussing what the rules require, we have to discuss what the rules do not say and what decides more than all the rest: how high the pump sits relative to the water level.

A centrifugal pump does not draw air. It can move water, but it cannot fill itself with water if it has to lift that water from below. If the pump sits below the pool’s water level, water enters it under its own weight and the pump runs flooded: it always starts, it primes itself, and after a power cut it goes back to work with nobody doing anything. If it sits above, there is a suction lift to overcome, which means priming it by hand every time it loses the water in its strainer basket.

A pump above the water is not a mistake you notice on day one. You notice it a month later, when the mechanical seal starts to weep because it has run dry a few times; and you notice it on the bill, because a cavitating pump moves less water for the same consumption.

And it comes with a second rule, this one purely geometric: every metre of pipe and every bend costs pressure. The plant room wants to be close to the pool and low. When somebody pushes it to the far end of the plot "so it is neither seen nor heard", they are buying less noise in exchange for a bigger pump, higher consumption every month and a harder prime. It is a legitimate trade, but it should be made knowing what is being traded.

What the rules require, now that they require something

Numeral 10.7 of Resolución 929 is short and a good deal harder than it looks when skimmed. This is what it asks for, broken out:

Two of those twelve deserve separate comment, because they are the ones most often breached and the cheapest to comply with.

The hydraulic schematic hung in the room. When a pool is sold, changes building manager, or simply breaks down on a Sunday, what decides whether the problem takes an hour or three days is whether anybody knows what each valve does. That drawing costs what it costs to print; not having it costs every single time something happens.

Exclusive use. This is the requirement that turns the most widespread practice in the country into a breach: the plant room as a store cupboard. And it is not a regulatory fussiness. A shared room is a room that people walk into without knowing what they are touching, with a pump running and water on the floor.

What the electrical rules do NOT require, and everybody thinks they do

Here an absence has to be declared, because it is the source of a fair number of inflated quotations.

I searched Book 3 of the RETIE in force and the pool section of the NTC 2050 for a requirement of forced ventilation, a minimum IP rating or a dedicated electrical panel for a pool plant room. There is none. The only thing the electrical code demands of the room itself is this:

What RETIE does require, and requires strictly, concerns the installation and not the room: equipotential bonding of metal parts with a copper conductor no smaller than 8 AWG, residual-current protection, and conduit resistant to corrosive environments — no aluminium — wherever the environment is corrosive. That is covered in detail in the article on spas, where electricity is the central question.

The emergency stop goes outside

This point straddles two sets of rules and both point the same way, so there is no room for interpretation.

Ley 1209 requires the manual pump stop to be in a visible place, signposted as such and freely accessible. And RETIE requires the disconnecting means to be readily accessible, within sight of the equipment it disconnects, and at least 1.5 m horizontally from the interior walls of the pool or spa.

Put the two together and the result is awkward for the usual design: the stop cannot be inside the plant room under a padlock, which is where it almost always is. An emergency button you have to go and fetch a key for is not an emergency button.

What has to fit, and how much room each thing needs

The minimum list for an ordinary domestic pool, in the order the water passes through them:

1. 1Strainer basket — the pot that catches leaves and hair before the pump. It is opened daily in season, so its lid needs to be reachable without moving anything.
2. 2Recirculation pump. With side clearance to take it out without cutting pipework.
3. 3Filter. This is the piece that governs the size of the room, and it is explained below.
4. 4Multiport valve or valve bank, with its labelling.
5. 5Pressure gauge on each filter. The rule expressly requires one as a blockage-control device.
6. 6Flow meter on the injection pipe, downstream of filtration. Also required.
7. 7Dosing or salt chlorination, depending on the disinfection system.
8. 8Heating, if there is any, with its own clearances and its own ventilation if it is gas-fired.
9. 9Electrical panel and controls, as far as possible from any chemical vapour.

The piece that decides the size of the room is the filter, and not for the space it takes up but for the space it needs around it:

• —Headroom above it. To open the top lid and lift out the diffuser you need, above the filter, something close to the height of the filter itself. A room with the slab just above the equipment is a room where the filter cannot be opened.
• —Room to take it out whole. A sand filter has to be replaced at some point, and the medium is exhausted. If the room was built with the filter inside and the door is sixty centimetres wide, that filter never comes out again.
• —Clear front for the valve. The multiport is operated weekly; it has to be done standing up and without contortions.

The numbers that size the machine

The size of pump and filter is not chosen from the volume of the pool but from the turnover time: how long the system takes to pass a volume equal to all the water through the filter. Resolución 929 sets it by type of use.

Look at the last row, because it settles an entire article: a spa calls for half an hour of turnover and a pool calls for four to six. They are different systems by law, not by taste. What that means when somebody wants both from a single machine is set out in a pool and a spa together.

And the rest of the figures the rule sets for the installation:

Noise, which is what people actually complain about

A pool pump runs between four and eight hours a day, and if the system is heated or there is a spa, longer. In a house you hear it; in a community of owners you hear it and somebody complains about it.

The temptation is to move the room further away, and we have seen what that costs. The remedies that do not penalise the hydraulics are different ones: sitting the pump on an elastomeric base instead of bolting it rigidly to the slab, putting flexible connectors on suction and discharge so the vibration does not travel down the pipe, and running filtration outside sleeping hours. None is expensive if decided early; all are awkward afterwards.

Ten questions before accepting the room

They work for reviewing a design on paper and for taking over a finished job. If any is answered no, something needs correcting while it is still cheap:

1. 1Does the pump sit below the water level of the pool?
2. 2Does a person working fit, or only the equipment?
3. 3Is there headroom above the filter to open it?
4. 4Does the filter fit through the door, assembled?
5. 5Does the floor fall to a drain, and does the drain have a grating?
6. 6Are the chemicals in a physically separate enclosure?
7. 7Are the valves labelled and the pipes marked with the direction of flow?
8. 8Is the hydraulic schematic of the system hung up?
9. 9Is the emergency stop outside, in view, signposted and without a key?
10. 10Is there a fire extinguisher inside the room?

How much this item weighs

I am not going to give figures here, and not out of caution but out of division of labour: what a pool costs and what it costs each month are dealt with in what a pool costs. What does belong in this article is what the underestimate is made of, because it is always the same:

• —The room gets priced and not the machine: walls and slab, with no equipment and no installation.
• —It is sized by whatever space was left over and then has to be enlarged, which is building it twice.
• —The electrical supply run to the room is forgotten, and it is usually the longest line in the project.
• —The separate chemical enclosure is forgotten, and it is now compulsory.
• —The floor drain is forgotten, and if it was not cast in it gets solved by breaking out.

Why we are writing this

Whoever leads this line of work in the studio brings fifteen years of designing hydraulic systems and bodies of water: drinking water and waste water plants, pools and water play in Bogotá between 2007 and 2012, and between 2019 and 2022 infinity-edge pools, spas and waterfalls with the systems behind them — pipe networks, filtration plants, pumps and plant rooms — in the Bahamas, Bermuda, Turks & Caicos and Miami.

From that experience comes the only conclusion that really matters here: the pools that give trouble rarely give it because of the shell. They give it because of what is behind that door.