Infinity Edge Pool Plumbing

[bbradsby]

Hi TV Pool Wizards,

So... am looking at self-building an infinity edge pool, and wonder how to size the basin or tank that captures the infinity edge overflow so that the pump doesn't ever catch air (cavitate) and burn out, and also big enough so that it doesnt overflow and flood the garden due to pump under-sizing? Is there a system diagram anyone can point me toward that shows how this type of system works? So far, Google's not been my friend...

thx in advance!

[PoolDoctor]

This is somewhat of a complicated equation. Why? Because there are a number of variables for the inputs. E.g., what is the maximum expected pool load (each person displaces 35 liters about), surface area exposure to rain (1 cm rain fall over a 8mx12m pool displaces about 960 liters), etc. Then, there is the distance from the pump to the pool - e.g., how quickly is the water drawn from the tank, and sent back to the pool so that it starts overflowing again. The shorter that distance, the less "buffer" water needed in the tank or catch basin.

We design the infinity catch tank to accomodate enough water, but as you said, not too much to lead to overflowing into the garden, causing erosion, loss of chemicals, etc. Finally, there is a "fudge factor" that we build in based on our own experience. Then, there is the length and height of the spill weir, which takes up water as it cascades. All of this, we have captured in our own spreadsheet.

PM me if you need.

Gil

The Pool Doctors

[bbradsby]

Many thanks for the detailed response!

I kinda figured some of it out, but not everything you mentioned, and it gets interesting since the 'infinity edge' (dontcha love marketingBS-speak?) becomes an air gap - below the water level in the pool!!! - in what would be an otherwise closed-loop system. For resort pools, I'm used to seeing [my pool consultants design] large surge tanks to temporarily accommodate the water displaced by fifty people or so, but we're not seeing 'Infinity Edge' pools Stateside much, likely because all resort clients either are lawyers or have their legal counsel on speed dial, and the slip & fall risks from drunks and/or unsupervised children seem countless for this edge design.

For this pool villa, the Aussie owner (my client) wants to take on the pool system design as a kind of puzzle, and he is a mathematician! I've advised him I'm very far from being a pool designer, and that getting it wrong may result in garden floods and/or pumps being burnt out. I love his spirit, as back in the Colonies, clients just press #1 to ring up their legal counsel and make these horrible whinging sounds if the universe is not perfect.

In the end, the client will have a go at it, but possibly may need your expertise in the future.

[AllanB]

This is somewhat of a complicated equation. Why? Because there are a number of variables for the inputs. E.g., what is the maximum expected pool load (each person displaces 35 liters about), surface area exposure to rain (1 cm rain fall over a 8mx12m pool displaces about 960 liters), etc. Then, there is the distance from the pump to the pool - e.g., how quickly is the water drawn from the tank, and sent back to the pool so that it starts overflowing again. The shorter that distance, the less "buffer" water needed in the tank or catch basin.

We design the infinity catch tank to accomodate enough water, but as you said, not too much to lead to overflowing into the garden, causing erosion, loss of chemicals, etc. Finally, there is a "fudge factor" that we build in based on our own experience. Then, there is the length and height of the spill weir, which takes up water as it cascades. All of this, we have captured in our own spreadsheet.

PM me if you need.

Gil

The Pool Doctors

If you are going to award yourself the elevated title of "doctor", it would be a good idea to know what you are talking about.

1. Then, there is the distance from the pump to the pool - e.g., how quickly is the water drawn from the tank, and sent back to the pool so that it starts overflowing again. The shorter that distance, the less "buffer" water needed in the tank or catch basin.The distance between pump and trough is totally irrelevant as all those pipes are always full of water and fluids are incompressible. Der!!

2. Then, there is the length and height of the spill weir, which takes up water as it cascades. What difference does that make, water falls quickly at the speed of gravity, the fraction of a second it takes to fall is irrelevant? We are not talking about the Angel Falls.

3. We design the infinity catch tank to accomodate enough water, but as you said, not too much to lead to overflowing into the garden, causing erosion, loss of chemicals, You have no idea what you are talking about. If the trough is too small it will require constant filling during the summer, so the bigger the better and fit an auto-fill if you don't want to ruin the pump. I assume you will be fitting a simple overflow to take care of any excess rain water, so the garden will be safe, with a small tank there will be more overflowing. Big swimming pool into small tank???

The doctor would have you believe it is complicated so he can impress you. although he seems to find it complicated himself. It is a very simple equation, the ratio between the volume of pool and the trough. keep it below 20 to 1. for a domestic pool. Eg.,.if your pool is 40m3 build your trough 2m3 or larger

The number of people in the pool is not that easy to estimate and not really that relevant in terms of displacement (on domestic pools) as active people create a surge over the weir, so their actual "displacement" is only a factor if they are dead bodies. Worst case example. if 10 people are racing towards the weir they will create maximum flow over the weir, due to the surge wave.

A slightly bigger pump is a good idea for an infinity pool and the pump should be running when the pool is in use, unless you have a huge capacity trough. Certainly during periods of high occupancy.

Finally, a useful acronym for your Ausi mathematician, KISS, (keep it simple stupid), complicated means trouble, unless you like trouble from your client. To my mind there are too many complicated pools out there and they seldom work without problems, People grow huge plants over the pool, which pollutes the water, phosphates being your number one enemy by far, even our bag filters won't remove them.

Edited March 27, 2013 by AllanB

[SantiSuk]

This is somewhat of a complicated equation. Why? Because there are a number of variables for the inputs. E.g., what is the maximum expected pool load (each person displaces 35 liters about), surface area exposure to rain (1 cm rain fall over a 8mx12m pool displaces about 960 liters), etc. Then, there is the distance from the pump to the pool - e.g., how quickly is the water drawn from the tank, and sent back to the pool so that it starts overflowing again. The shorter that distance, the less "buffer" water needed in the tank or catch basin.

We design the infinity catch tank to accomodate enough water, but as you said, not too much to lead to overflowing into the garden, causing erosion, loss of chemicals, etc. Finally, there is a "fudge factor" that we build in based on our own experience. Then, there is the length and height of the spill weir, which takes up water as it cascades. All of this, we have captured in our own spreadsheet.

PM me if you need.

Gil

The Pool Doctors

If you are going to award yourself the elevated title of "doctor", it would be a good idea to know what you are talking about.

1. Then, there is the distance from the pump to the pool - e.g., how quickly is the water drawn from the tank, and sent back to the pool so that it starts overflowing again. The shorter that distance, the less "buffer" water needed in the tank or catch basin.The distance between pump and trough is totally irrelevant as all those pipes are always full of water and fluids are incompressible. Der!!

2. Then, there is the length and height of the spill weir, which takes up water as it cascades. What difference does that make, water falls quickly at the speed of gravity, the fraction of a second it takes to fall is irrelevant? We are not talking about the Angel Falls.

3. We design the infinity catch tank to accomodate enough water, but as you said, not too much to lead to overflowing into the garden, causing erosion, loss of chemicals, You have no idea what you are talking about. If the trough is too small it will require constant filling during the summer, so the bigger the better and fit an auto-fill if you don't want to ruin the pump. I assume you will be fitting a simple overflow to take care of any excess rain water, so the garden will be safe, with a small tank there will be more overflowing. Big swimming pool into small tank???

The doctor would have you believe it is complicated so he can impress you. although he seems to find it complicated himself. It is a very simple equation, the ratio between the volume of pool and the trough. keep it below 20 to 1. for a domestic pool. Eg.,.if your pool is 40m3 build your trough 2m3 or larger

The number of people in the pool is not that easy to estimate and not really that relevant in terms of displacement (on domestic pools) as active people create a surge over the weir, so their actual "displacement" is only a factor if they are dead bodies. Worst case example. if 10 people are racing towards the weir they will create maximum flow over the weir, due to the surge wave.

A slightly bigger pump is a good idea for an infinity pool and the pump should be running when the pool is in use, unless you have a huge capacity trough. Certainly during periods of high occupancy.

Finally, a useful acronym for your Ausi mathematician, KISS, (keep it simple stupid), complicated means trouble, unless you like trouble from your client. To my mind there are too many complicated pools out there and they seldom work without problems, People grow huge plants over the pool, which pollutes the water, phosphates being your number one enemy by far, even our bag filters won't remove them.

Not sure I follow the logic of running the pump when swimming Allan. I do the converse if all the splashy kids are coming - i.e. empty about one inch off the pool and into the reserve tank via the side troughs and switch off the pumps. That way I conserve treated pool water and the electricity to pump well water to replace the stuff the kids would otherwise wash away into the garden. [They manage to do some anyway!]

Bit boring to do (with a large bucket - I guess I should treat myself to a submersible pump) and I can only be @rsed to do it 50% of the time. I have a reserve tank that will take up to 5% of the pool volume though and I do hang around to make sure that the pool refills afterwards without sucking the reserve tank dry.

[AllanB]

This is somewhat of a complicated equation. Why? Because there are a number of variables for the inputs. E.g., what is the maximum expected pool load (each person displaces 35 liters about), surface area exposure to rain (1 cm rain fall over a 8mx12m pool displaces about 960 liters), etc. Then, there is the distance from the pump to the pool - e.g., how quickly is the water drawn from the tank, and sent back to the pool so that it starts overflowing again. The shorter that distance, the less "buffer" water needed in the tank or catch basin.

We design the infinity catch tank to accomodate enough water, but as you said, not too much to lead to overflowing into the garden, causing erosion, loss of chemicals, etc. Finally, there is a "fudge factor" that we build in based on our own experience. Then, there is the length and height of the spill weir, which takes up water as it cascades. All of this, we have captured in our own spreadsheet.

PM me if you need.

Gil

The Pool Doctors

If you are going to award yourself the elevated title of "doctor", it would be a good idea to know what you are talking about.

1. Then, there is the distance from the pump to the pool - e.g., how quickly is the water drawn from the tank, and sent back to the pool so that it starts overflowing again. The shorter that distance, the less "buffer" water needed in the tank or catch basin.The distance between pump and trough is totally irrelevant as all those pipes are always full of water and fluids are incompressible. Der!!

2. Then, there is the length and height of the spill weir, which takes up water as it cascades. What difference does that make, water falls quickly at the speed of gravity, the fraction of a second it takes to fall is irrelevant? We are not talking about the Angel Falls.

3. We design the infinity catch tank to accomodate enough water, but as you said, not too much to lead to overflowing into the garden, causing erosion, loss of chemicals, You have no idea what you are talking about. If the trough is too small it will require constant filling during the summer, so the bigger the better and fit an auto-fill if you don't want to ruin the pump. I assume you will be fitting a simple overflow to take care of any excess rain water, so the garden will be safe, with a small tank there will be more overflowing. Big swimming pool into small tank???

The doctor would have you believe it is complicated so he can impress you. although he seems to find it complicated himself. It is a very simple equation, the ratio between the volume of pool and the trough. keep it below 20 to 1. for a domestic pool. Eg.,.if your pool is 40m3 build your trough 2m3 or larger

The number of people in the pool is not that easy to estimate and not really that relevant in terms of displacement (on domestic pools) as active people create a surge over the weir, so their actual "displacement" is only a factor if they are dead bodies. Worst case example. if 10 people are racing towards the weir they will create maximum flow over the weir, due to the surge wave.

A slightly bigger pump is a good idea for an infinity pool and the pump should be running when the pool is in use, unless you have a huge capacity trough. Certainly during periods of high occupancy.

Finally, a useful acronym for your Ausi mathematician, KISS, (keep it simple stupid), complicated means trouble, unless you like trouble from your client. To my mind there are too many complicated pools out there and they seldom work without problems, People grow huge plants over the pool, which pollutes the water, phosphates being your number one enemy by far, even our bag filters won't remove them.

Not sure I follow the logic of running the pump when swimming Allan. I do the converse if all the splashy kids are coming - i.e. empty about one inch off the pool and into the reserve tank via the side troughs and switch off the pumps. That way I conserve treated pool water and the electricity to pump well water to replace the stuff the kids would otherwise wash away into the garden. [They manage to do some anyway!]

Bit boring to do (with a large bucket - I guess I should treat myself to a submersible pump) and I can only be @rsed to do it 50% of the time. I have a reserve tank that will take up to 5% of the pool volume though and I do hang around to make sure that the pool refills afterwards without sucking the reserve tank dry.

You must have quite a large trough/tank and that is good, then what you say makes sense, if not, with a lot of activity the trough/tank could overflow due to the accumulative effect of the surges.

It you have high water level in your pool and/or no swan neck edge you, will lose some into the garden and if the little beggers are doing bombs, it don't much matter anyway, the garden gets watered.

Infinity pools are my favourite, the most efficient for keeping clean and given the right environment, the most attractive. Some of the ones I have seen are absolutely stunning and all crystal clear.

[Chaichara]

I'm not much of a mathematician, but if I remember my primary school maths from nearly 60 years ago, if a person weighs, say 120 Kg (like me - old and overweight), if s/he is totally submerged, s/he will displace around 120 litres of water, being the volume of that persons body, which of course is a tad lighter than water, otherwise people wouldn't float. So the doctor's 35 litres would be about right for a teenage kid standing waist deep in the water.

I heard somewhere that ideally, the surge tank should have a capacity of 10% based on the pool volume, but probably somewhat smaller would be OK. The actual size of the tank would need to be able to accomodate the surge without wasting water through its overflow - that's were a lot of people's water seems to go when the surge (sometimes called balance tank) tank is too small.

Overflow and infinity edge pools tend to loose more water than skimmer pools due to increased evaporation from the hot surfaces the water runs over and through the gutter, and loss from genral mist spray.

Cavitation is not an issue. You will get some bubbles in the water cause by cavitation from the pump impeller, the same phenomenon is caused ships propellors. In some rare cases, cavitation can cause pitting of the impeller metal, but as far as I know, this is rare in pool pumps.