Building a swimming pool is a big project, and the decisions you make at the very start, the type of pool, where it goes and how the water circulates, shape how well it runs and what it costs for years afterwards. This guide covers what to consider, including the increasingly popular natural swimming pond, and one point that is easy to leave too late: the pump. In any pool or pond, the circulation pump is the heart of the system, and it is best specified at the design stage, not bolted on at the end.
First decision: a conventional pool or a natural swimming pond?
These are two quite different things, and it is the fork that shapes everything else.
A conventional pool is filtered mechanically and kept clean chemically, usually with chlorine, or with a salt chlorinator (more on that below). The water is clear, controlled and flow-maintenance in a predictable way.
A natural swimming pond, also called a natural swimming pool, is chemical-free. Instead of chlorine, the water is cleaned biologically by aquatic plants and beneficial bacteria in a dedicated planted zone. They have become popular for people who want chemical-free, wildlife-friendly swimming that looks like part of the garden. They are beautiful, but they depend absolutely on good circulation, as we will come to.
If you are building a conventional pool
Indoor or outdoor?
In the UK, an outdoor pool is largely seasonal unless heated, and simpler to build. An indoor pool means a building to house it, which brings heating, ventilation and dehumidification into the picture (pool halls need humidity control or the structure suffers), and a bigger budget. Indoor pools are a year-round luxury but a much larger undertaking.
Construction type
In-ground pools are typically concrete or gunite (fully bespoke), a lined shell, or a one-piece fibreglass unit. Above-ground pools are cheaper and quicker but shorter-lived. Size, depth and intended use, family splashing, lap swimming, a plunge pool, all follow from here.
Do you need planning permission?
For a straightforward outdoor domestic pool in your garden, planning permission is often not required, as it can fall under permitted development. But there are important exceptions: listed buildings, conservation areas, National Parks and Areas of Outstanding Natural Beauty have tighter rules, and any building or enclosure to house the pool, such as an indoor pool hall, usually will need permission and must meet Building Regulations, including the electrical work. This is general guidance, not a ruling, so always check with your local planning authority before you start.
Chlorine or salt water?
A "salt water pool" is a common source of confusion. It does not mean a chemical-free pool. A salt water pool is a conventional pool with a salt chlorinator: you add salt, and the unit converts it into chlorine to sanitise the water. It is gentler on the eyes and skin than dosing with chlorine directly, but it is still a chlorinated pool. The important build consequence is that salt is corrosive, so the pump and fittings must be salt-tolerant, which is why we would point a salt pool at a corrosion-resistant pump such as the Plastica AG or Argonaut in our range.
Plastica Argonaut AV swimming pool pump shown beside a natural swimming pool.
Heating and running costs
Heating (usually a heat pump in the UK) and the pump are the two big energy users. Because the pump runs long hours, choosing an efficient, correctly sized one, and increasingly a variable speed pump, makes a real difference to running costs. We cover this in pool pump running costs and how to reduce them.
Natural swimming ponds: planting and circulation
A natural swimming pond is built in two connected zones. There is the swimming zone, clear and deep enough to swim in, and a separate regeneration zone, planted with aquatic plants growing in gravel. The plants and the bacteria on the gravel take up the nutrients that would otherwise feed algae, which is what keeps the water clean without chemicals.
Planting is chosen to do a job, not just to look good: oxygenating plants, marginals and reeds strip nutrients from the water and add oxygen. But planting alone is not enough. The water has to be moved continuously between the swimming zone and the regeneration zone, so it is constantly being filtered and oxygenated. That circulation is driven by a pump, and if the circulation is poor the pond stagnates no matter how good the planting is. In a natural pond, the hydraulics matter as much as the horticulture, which is why the same continuous-duty principles as a pond pump apply: a low-energy pump, running continuously, sized to turn the water through the plant filter.
What about a salt water natural pond?
This is an emerging and more specialist option. A conventional salt chlorinated pool (above) is not a natural pond. But it is possible to create a low-salinity or brackish natural pond planted with salt-tolerant (halophyte) plants, such as certain rushes and coastal species, for a different look and ecology. It is a niche approach and the plant selection is specialist, so it is one to design with an expert. Whichever way you go, the water still has to be circulated properly, so the pump and its layout remain central.
Building a swimming pool is a big project, and the decisions you make at the very start, the type of pool, where it goes and how the water circulates, shape how well it runs and what it costs for years afterwards. This guide covers what to consider, including the increasingly popular natural swimming pond, and one point that is easy to leave too late: the pump. In any pool or pond, the circulation pump is the heart of the system, and it is best specified at the design stage, not bolted on at the end.
First decision: a conventional pool or a natural swimming pond?
These are two quite different things, and it is the fork that shapes everything else.
A conventional pool is filtered mechanically and kept clean chemically, usually with chlorine, or with a salt chlorinator (more on that below). The water is clear, controlled and low-maintenance in a predictable way.
A natural swimming pond, also called a natural swimming pool, is chemical-free. Instead of chlorine, the water is cleaned biologically by aquatic plants and beneficial bacteria in a dedicated planted zone. They have become popular for people who want chemical-free, wildlife-friendly swimming that looks like part of the garden. They are beautiful, but they depend absolutely on good circulation.
If you are building a conventional pool
Indoor or outdoor?
In the UK, an outdoor pool is largely seasonal unless heated, and simpler to build. An indoor pool means a building to house it, which brings heating, ventilation and dehumidification into the picture (pool halls need humidity control or the structure suffers), and a bigger budget. Indoor pools are a year-round luxury but a much larger undertaking.
Construction type
In-ground pools are typically concrete or gunite (fully bespoke), a lined shell, or a one-piece fibreglass unit. Above-ground pools are cheaper and quicker but shorter-lived. Size, depth and intended use, family splashing, lap swimming, a plunge pool, all follow from here.
Do you need planning permission?
For a straightforward outdoor domestic pool in your garden, planning permission is often not required, as it can fall under permitted development. But there are important exceptions: listed buildings, conservation areas, National Parks and Areas of Outstanding Natural Beauty have tighter rules, and any building or enclosure to house the pool, such as an indoor pool hall, usually will need permission and must meet Building Regulations, including the electrical work. This is general guidance, not a ruling, so always check with your local planning authority before you start.
Chlorine or salt water?
A "salt water pool" is a common source of confusion. It does not mean a chemical-free pool. A salt water pool is a conventional pool with a salt chlorinator: you add salt, and the unit converts it into chlorine to sanitise the water. It is gentler on the eyes and skin than dosing with chlorine directly, but it is still a chlorinated pool. The important build consequence is that salt is corrosive, so the pump and fittings must be salt-tolerant, which is why we would point a salt pool at a corrosion-resistant pump such as the Plastica AG or Argonaut in our range.
Heating and running costs
Heating (usually a heat pump in the UK) and the pump are the two big energy users. Because the pump runs long hours, choosing an efficient, correctly sized one, and increasingly a variable speed pump, makes a real difference to running costs. We cover this in pool pump running costs and how to reduce them.
Natural swimming ponds: planting and circulation
A natural swimming pond is built in two connected zones. There is the swimming zone, clear and deep enough to swim in, and a separate regeneration zone, planted with aquatic plants growing in gravel. The plants and the bacteria on the gravel take up the nutrients that would otherwise feed algae, which is what keeps the water clean without chemicals.
Planting is chosen to do a job, not just to look good: oxygenating plants, marginals and reeds strip nutrients from the water and add oxygen. But planting alone is not enough. The water has to be moved continuously between the swimming zone and the regeneration zone, so it is constantly being filtered and oxygenated. That circulation is driven by a pump, and if the circulation is poor the pond stagnates no matter how good the planting is. In a natural pond, the hydraulics matter as much as the horticulture, which is why the same continuous-duty principles as a pond pump apply: a low-energy pump, running continuously, sized to turn the water through the plant filter.
What about a salt water natural pond?
This is an emerging and more specialist option. A conventional salt chlorinated pool (above) is not a natural pond. But it is possible to create a low-salinity or brackish natural pond planted with salt-tolerant (halophyte) plants, such as certain rushes and coastal species, for a different look and ecology. It is a niche approach and the plant selection is specialist, so it is one to design with an expert. Whichever way you go, the water still has to be circulated properly, so the pump and its layout remain central.
The same thinking as sustainable drainage (SuDS)
If a natural swimming pond sounds like a niche garden idea, it is worth knowing that the principle behind it is used at a much larger scale in civil engineering. Sustainable Drainage Systems, or SuDS, manage rainwater runoff by mimicking nature rather than piping it straight away, and they rely on the very same idea that makes a natural pond work: the right plants, in the right layout, clean and condition the water. In a SuDS scheme, features such as balancing ponds, attenuation basins and wetlands use planting and the biology around it to slow the water, drop out sediment, and strip nutrients and pollutants before it moves on. It is a natural swimming pond's regeneration zone, scaled up and engineered.
This is exactly the kind of design our sister company, FPS Environmental, works with when planning SuDS schemes and balancing ponds: selecting planting for water quality, and getting the flows and circulation right so the system stays healthy over time. Whether it is a garden natural pool or a development-scale drainage pond, success comes down to the same two things, the planting and the way the water moves. And moving the water is where a well-chosen pump comes in.
Why the pump should be specified at the build stage
Whether it is a chlorinated pool, a salt pool or a natural pond, the circulation pump is what keeps the water moving, filtered and healthy, and it is far easier and cheaper to get right during design than to fix afterwards. Two numbers define it: the flow needed to circulate the whole volume through the filter or regeneration zone within a set turnover time, and the head needed to overcome the pipework, filter, heater and any features. Get it wrong and you pay for it, an undersized pump cannot keep the water clear, and an oversized one wastes energy and strains the system.
You will most likely be working with a pool builder or an engineer who designs the hydraulics, and that is the right way to do it. But if you want to get a feel for the pump you will need, you can try the free calculator on our swimming pool pumps page, which sizes a pump from your pool volume and pipework. Our guide on how to size a swimming pool pump explains the method, and for a proper specification our engineering review service can help. It also pays to choose the right brand for the job, our guide to the Plastica range and the best swimming pool pumps is a good place to start.
The pump specialists behind your pool
floodandwaterpumps.co.uk is the UK's leading pump stockist, led by an environmental and engineering team, and we are as much at home specifying a pool or natural pond pump as a flood or borehole one. If you are planning a build, talk to us early about the circulation, it is the decision that keeps the water right for years. Browse the swimming pool pumps range, use the calculator, or call our engineers on 0115 987 0358.
