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That horizon of water is cleverer than it looks
You have probably seen the photos. A still sheet of water seems to run right off the edge of the garden and melt into the hills, the sea or the sky. It looks almost like magic. In fact, an infinity pool is a very clever piece of engineering that uses gravity, a hidden basin and a pump to create that effect.
We get asked about them a lot. Some people have fallen in love with a holiday villa. Others have a garden with a gentle slope and a lovely view, and wonder if they could make the most of it.
In this guide we’ll explain, in plain English, how the vanishing edge works, what goes on out of sight, which gardens suit this style best, and what it means for running and care. We’ll also be honest about the downsides. That way you can decide with a clear head whether it’s right for your home.
A quick word on the name
You’ll hear a few names for the same idea. Vanishing edge, negative edge, zero edge and disappearing edge all describe the same thing. One or more sides of the pool are built slightly lower than the water level, so the water spills over and out of sight.
An infinity pool works by letting water spill over one lowered edge
In a normal pool, the water sits a little below the top of the walls. It stays put, and the only water leaving the pool goes into the skimmers and drains to be filtered.
A vanishing edge pool is different. At least one wall is built so its top sits exactly at the water line. Water flows gently over that wall all the time the system is running. From the right viewpoint, you can’t see the wall at all. You just see water, and then the view.
Where does the water go?
It doesn’t disappear, of course. It falls into a channel or catch basin that runs along the outside of the lowered wall, just below it. From there it flows into a balance tank, which is a hidden reservoir that holds the spare water.
How does it get back?
A pump draws water from the balance tank, sends it through the filter and any heating, and returns it to the main pool. The main pool fills up again, spills over the edge again, and the loop keeps going. It’s a closed circuit, so the same water is being cycled round and round.
Why the level has to be spot on
The whole effect depends on the edge being perfectly level along its full length. If one end sits even slightly higher, the water will pour over one part and leave another part dry. That breaks the illusion straight away. So the edge has to be built with real precision, and the water level has to be managed carefully so the flow stays smooth and even.
Every part has a job to do behind the scenes
When you look at an infinity pool, you only see the pretty part. Behind it sits a whole system that keeps the water moving and the level steady. Here are the main parts and what each one does.
The weir or vanishing wall
This is the lowered wall the water flows over. Its top edge is carefully finished so the water spreads into a thin, even sheet. The finish and material matter, because a rough or uneven lip shows up straight away in the way the water falls.
The catch basin or trough
This sits below and just outside the vanishing wall. It catches the water as it tips over and channels it away. It’s often hidden behind planting or a lower wall, so from the house you don’t see it.
The balance tank
The balance tank is the unsung hero of the system. It holds the water that has overflowed, plus extra to cover the times when lots of people get in and push water over the edge. It also has to hold what drains back when the pump switches off. Because of all this, it needs to be bigger than the tank you’d find on a standard overflow pool.
The pump and filtration
The pump is what keeps the edge flowing. It lifts water from the balance tank back into the main pool. Because it’s moving a steady stream over the edge, it often needs to be larger than on an ordinary pool, and it may run for longer. The water still passes through the filter, and it can be heated too if you have a heater fitted.
The pipework and automatic top up
There’s more pipework than usual, linking the pool, the basin, the tank and the plant room. Most systems also have an automatic top up, which adds fresh water when the level drops. This matters because water is lost more quickly with this style of pool, as we’ll explain below.
Infinity pools look their best on sloping sites with a view
This is where we need to be honest. A vanishing edge is stunning in the right place, but it isn’t right for every garden.
The ideal setting
The effect works best when the ground falls away beyond the pool. That drop means you can’t see the catch basin from the house or the terrace, and the water seems to run straight into whatever lies beyond. Good examples include:
- A garden on a hillside with views across open countryside
- A plot that looks out over the sea, a lake or a river
- A raised terrace that overlooks a lower lawn or a valley
- A garden with a long, uninterrupted view to the horizon
When it may not be the best choice
On a flat garden with a fence or hedge at the end, the effect loses much of its point. Instead of melting into a view, the water appears to spill towards the neighbour’s boundary. You’d also need to dig down or build up to hide the basin, which adds work and cost without the reward.
Other finishes worth considering
If you love the look of water brimming right up to the edge, there are other options. A flush or overflow style finish, where the water sits level with the surrounding paving on all sides, gives a sleek, modern look that suits many flat gardens beautifully. It’s worth talking these through before you settle on a design.
There are real trade-offs to weigh up before you commit
An infinity pool adds drama and a real sense of luxury. It also adds complexity. Here’s a balanced look at both sides.
What people love about them
- The view becomes part of the pool, and the pool becomes part of the view
- The water surface stays glassy and calm, which looks beautiful day and night
- The gentle sound of flowing water can be very relaxing
- They make the most of a tricky sloping plot that might otherwise be hard to use
- They can add a real wow factor to a home and garden
What you need to be ready for
- Extra engineering. The pool, the basin and the ground below all need careful structural design, especially on a slope. Retaining walls and deeper foundations are often needed.
- More water loss. With water constantly moving and falling, more is lost to evaporation and splash. Wind can make this worse. You’ll top up more often than with a standard pool.
- More heat loss. A larger, moving water surface loses warmth faster, so heating works harder. Our guide to swimming pool heating explains how to keep that in check.
- More kit. A bigger balance tank, more pipework and often a larger pump all add to the build.
- Noise. Some people love the sound of running water. Others find it too much close to a bedroom window. The drop and the design of the basin make a difference here.
- Planning. Because of the retaining walls, raised sections and changes to ground levels on sloping sites, you may need planning permission. It’s always worth checking with your local council early on.
A word on cost
With all that extra work, a vanishing edge will cost more than a standard pool of the same size. How much more varies a great deal from site to site. It depends on the slope, the ground conditions, access and the finish you choose. We’ll always give you a tailored quote rather than a guess, and our guide to swimming pool cost explains the main things that shape the price.
Running and caring for an infinity pool takes a little more effort
Much of the care is the same as any pool. You’ll still test and balance the water, keep the filter clean and brush the surfaces. But there are a few extra jobs to build into your routine.
Keeping the edge clean
The vanishing wall is on show all the time, so it needs to look its best. Over time, limescale, algae and grime can build up along the lip and on the face of the wall. This spoils the smooth sheet of water. A gentle, regular clean keeps it looking crisp.
Looking after the catch basin
Leaves, insects and debris that flow over the edge end up in the basin. Clear it out regularly, especially in autumn. A blocked basin can overflow or starve the pump of water.
Watching the water level
The automatic top up does most of the work, but it’s worth keeping an eye on it. If you notice you’re adding far more water than usual, it could be a sign of a problem that needs checking. Higher use is normal on a hot, windy day, though. For more ideas, take a look at our article on rooftop swimming pools.
Running costs
Because the pump often works harder and for longer, and you may be heating more water, running costs tend to be higher. A pool cover helps a lot when the pool isn’t in use. You can switch the edge off at quiet times too, which saves energy and cuts water loss. Take a look at our guide to pool running costs for practical ways to keep bills down. If you’re weighing up your options, our guide to the latest swimming pool trends is worth a look.
Winter care
In winter you’ll usually reduce how often the edge runs, or switch it off. Your installer can advise on the best way to protect the balance tank, pipework and pump during the colder months. Our guide to swimming pool design covers this in more detail.
Infinity pool questions we get asked a lot
Is a vanishing edge pool safe for children?
It can be, with the right design and supervision. The water depth and the drop beyond the edge both need thought, especially on steep sites, so talk safety through with your designer early.
Can I switch off the overflow?
Yes. Most systems let you turn the edge off, so the pool behaves like a normal one. Many owners run it for a few hours when they’re using or enjoying the pool, then switch it off.
Does the water actually drop off a cliff?
No. It falls a short way into a hidden basin just below the edge. From your viewpoint it looks as though it vanishes, but it’s all caught and recycled.
Will I lose a lot of water?
You’ll lose more than with a standard pool, mainly through evaporation and splash. An automatic top up takes care of most of this, and a cover helps a great deal.
Do I need planning permission?
It depends on your site and design. Raised sections, retaining walls and big changes to ground levels can all bring planning into play, so check with your local council before work starts.
Can I have one on a flat garden?
You can, but the effect is less striking without a view or a drop beyond. On a flat plot, a flush or overflow style finish may give you the look you want more simply.
Let’s talk about whether an infinity pool suits your garden
A vanishing edge can turn a lovely view into something truly special. It does take more planning, more engineering and a little more care, so it’s worth thinking it through with someone who knows pools inside out.
If you’re dreaming of water that seems to meet the sky, we’d love to hear about your garden. Talk to us about whether an infinity edge, or an alternative such as a flush or overflow style finish, suits your space. In the meantime, you can explore our full range of pools to see what’s possible.
Call us on 01483 323 676 or email hello@hilifepools.co.uk for a friendly, no-pressure chat, or get in touch online and we’ll come back to you.
