Operation of Infinity Edge and Zero Edge Pools

[setsailsoon]

Folks,

May of this year we filled up our brand new OB pool with a combination infinity edge and zero edge. I'm finding there are a few things that are a little different about its operation so I thought it might be helpful to others that I start this thread as a place where we can assemble learnings and tips specific to these types of pool. Here's my first entry:

My pool has a zero edge around all the edges and infinity over the back edge closest to the lake behind our lot. (recent photo below) 3' below this edge is a catch basin that has two large suction fittings in the bottom which is another 3' below. It's also 2' wide. I was very concerned during the design phase about how to control level since this little basin holds only ~1500 gal compared to the pool volume of 28,000 gal. Turns out it's very easy to control since there's way less time delay when people enter the pool and displace water over the infinity edge. I had planned to use a high level normal level and min level with some unnecessarily complex control. Turns out it's very easily controlled with a single simple float switch type level control set normally about 8" from the bottom. I use this to add water from my irrigation well pump via a pipe that fills the basin directly and it has a simple, inexpensive sprinkler valve. So long as the basin has plenty of volume to handle a lot of people this works great. Each time somebody gets in they displace 23 gal of water over the back edge. So even 5 or 6 is way less than my 1000+ gal capacity. For people that use the smaller horizontal buried surge tanks this could be a bigger issue. So while I was all consumed (over-consumed) with the level control response time I didn't think much about what happens if the level switch failed closed. Right after I added 3500 ppm salt and before I turned it on I had to take a business trip for a week. So I left and my wife just added liquid chlorine. I looked at the pool each day through the security camera that I accessed with my phone. After a few days the pool changed from it's normal gorgeous crystal clear to slightly greenish then deep green. We had massive amounts of rain that often happen this time of year in S Florida. So I had her add 4 ppm chlorine. This helped but didn't solve it so we doubled the addition. This cycle repeated till I was adding 10 ppm per day. This was LOT of chlorine since the pool is 28000 gal. But it was barely enough and 10 ppm is SLAM level for my CYA level (still low for this newish pool). When I finally got home after the flights from H**L we get these days it was 2 am so I went straight to bed. Woke up next day and thought I heard a pump running but that's normal for the irrigation pump. So I got up slowly, had a few cups of coffee and eventually wandered out to look at our gorgeous pool from the patio... only it was now really deep green and the back of my yard below the pool was flooded! Not from rain but from my pool. The level control had failed and ran the irrigation fill all week long 24 hours per day! The green color came from the tannins in the well water that are yellow until oxidized with chlorine. Yellow plus blue background from the plaster = green. Thanks @JoyfulNoise noise for that tip from construction when we first started it up. I quickly went to a manual mode on the level control and am now incorporating a high level shut down plus a low level shutdown to prevent pump damage. Very easy to do and yes, necessary for this type of pool.

I hope this is helpful to someone with a similar pool.

Chris

 

[Turbo1Ton]

Oh man... Tough lesson there. Shoulda hazop'd the pool systems.

Hopefully no damage to the irrigation pump/well.

I've said it in your build thread but I'll say it again here... the pool looks freaking amazing! Love the picture window enclosure and what it does for the view!

--Jeff

 

[kimkats]

Lessons learned and shared=well done!

Robin and I did good on that picture window

 

[JoyfulNoise]

This thread gave me heart palpitations

When we Arizonans hear “flooded backyard” and “irrigation ran for a week”, we quickly look up our checking account balances because the next water bill is going to be more expensive than a week-long, all-inclusive trip to a Disney theme park

Agree with your assessment - definitely need a low level trigger AND a high-level alarm and shutoff.

I’ve never liked using irrigation components for pool controls. I realize they are designed for outdoor use but they can fail easily and they really need constant maintenance (at least mine always did when I had an irrigation system … I don’t irrigate anymore). You can’t see the overflow basin easily everyday and so that makes it an “out of sight/out of mind” problem. You might consider either installing a cheap mirror to reflect the basin towards you so you can throw some eyes on it OR install another cheap security camera to be able to do a level check occasionally. I have a similar problem as my equipment pad is out of sight. So unless I force myself to do a daily stroll over there, things can (and have) gone be unnoticed.

Hope the tannins clear out soon. With so much water overflowing the basin, you may need to do a detailed water analysis to see how much dilution has affected your stabilizer and salt levels.

 

[Turbo1Ton]

installing a cheap mirror to reflect the basin towards you so you can throw some eyes on it

@Dirk - You hack Matt's account?

--Jeff

 

[Dirk]

@Dirk - You hack Matt's account?

--Jeff

His brain, not his account!

 

[JoyfulNoise]

His brain, not his account!

I suddenly had the desire to run 50 extra miles of Romex and Ethernet cabling all through my house … just in case I needed it!!!!

 

[Dirk]

I didn't quite understand the valve setup. If the sprinkler valve is followed by a float valve, you can't use a sprinkler valve in that application. And that might explain why it failed. Sprinkler valves are not rated to be under constant pressure on the output side. They're expecting a set of sprinklers, which only offer reduced pressure while on (because they're sprinkling) and no pressure when they are off (because the sprinklers drain off any residual pressure).

Unless the float valve is flowing, it's holding pressure in the line and against the sprinkler valve upstream of it, which puts constant pressure on the sprinkler valve's backflow control components (springs and whatnot), which it can't handle indefinitely. And if the float valve is in the water, you need a pressure vacuum breaker in the line, to prevent back-flow. Something like this is rated for constant pressure down-stream of itself:

Amazon.com

Then if you need automated shut off, a motorized valve is more appropriate than the solenoid of a sprinkler valve. They can be ordered "normally open," or "normally closed." So if they fail, or if there is a power failure, the valve will move (yes, even without power), to its normal position (whichever is best from a safety or non-flooding standpoint). Something like this:

Amazon.com

And unlike a sprinkler valve, which is only open when electricity is applied to its solenoid, a motorized valve only uses electricity to move from one position to the other. It stores a certain amount, so when electricity is not present, it has enough "juice" to move back to its normal position. And it has no springs or pressure plates or any of the other failure/maintenance points of a sprinkler valve, so it can handle constant pressure.

It terms of flood prevention, Matt has you on the right path (or a path). I rely on security cams for that. And I have small mirrors to peer around the corners my security cams can't. I like PTZ cams for this application (Pan, Tilt, Zoom), so I can move the lens around to see different things. I have one on my pool, and one on my pad, and there's only a few things those cams can't see. One of which is the end of my overflow pipe. And my auto-leveling system fails often enough for me to have to worry about it. So a small mirror placed just so allows me a view of that pipe from my pool cam.

I painted my pipe camo, so it's a little hard to see this time of day, but I know where it is, and I can very easily see when water is flowing out of it. I have one of the motorized valves I described above, and it closes at night, so I don't have to worry about an auto-filling failure at night. Mine is "normally open," so during a power failure it will reset to open, because I'd rather waste water than have my pool evaporate low enough to starve my $2000 pump!

This is from this morning, which reminds me, I have to clean off that mirror from when I hosed down the surrounding plants this hot, hot summer:


Here it is showing my pool overflowing last winter during a rain. I've since repainted the pipe, and moved the mirror, but you get the gist:



I've since put a little roof over the mirror (see first pic) to help keep heavy rains from obscuring the view. I ended up moving it due to the view being obscured by new plants, and because the mirror kept moving due to that wooden post expanding and contracting because of rain. I've since attached the mirror to the metal fence, and that solved for that.

The mirrors can be a bit fussy, and I'm still perfecting mine. The better solution is a cam located in line-of-sight of what you are monitoring. They make 'em for POE (Power Over Ethernet), so you only need one wire running to them, and they make 'em to withstand the elements, even heavy rain, so they can be just about anywhere you need them to be. Or you can go with a WiFi cam and power it from an outlet in the yard. But I don't like WiFi, so all my cams are hard-wired with POE.

Full disclosure: when you combine outdoor rated, plus waterproofing, and POE and PTZ and the kind of decent resolution you're seeing in my pics, cams can get up there in price (hundreds). But then, what's your peace of mind worth? Or you can go cheap with just about any outdoor, fixed, WiFi security cam.

You could also rig up a water sensor to detect flooding, but that gets tricky outdoors, when you have to find a solution that can detect a flooding pool but not a decent rain. And they are not infallible, when it comes to electronic failure. With a cam, if it's not working, it's very obvious. And when it is working, you get a literal visual confirmation of what you're monitoring, which is hard to beat when it comes to reliability.

 

[Dirk]

And if I haven't given our crew enough to rib me about this morning, here's another of my "inventions" for your consideration. Dubbed "The Pooler," (Pool Level Ruler). Yes, I mounted a ruler to the side of my pool! I have zero set at the bottom of my skimmer opening, so the ticks are telling me how much water I have in the pool above where my pump would get starved. It's easy enough to see my water level from my yard, but it isn't always obvious through my pool cam, depending on time of day and weather. So that's what inspired this admittedly kookie idea. This morning, my water level is 3.25" above the bottom of my skimmer opening, which is pretty much halfway up the skimmer. Right where it's supposed to be.

OK, as long as I'm suspending humility, the res on my pool cam is so high that I can see the level is actually 3-5/16" above my skimmer opening! It's only money!!

I looked at the overflow mirror a few minutes ago by pressing the "9" key on my laptop. Then I checked my water level by typing "0" just now (keyboard shortcuts assigned to moving my PTZ pool cam). So I can take the ribbing, especially considering I haven't even gotten out of bed yet this morning!

Perhaps a similar setup could be useful to monitor your catch basin, so you could peek at it from your phone the next time you find yourself in a hotel room somewhere.

 

[JoyfulNoise]

And hidden away amongst all that landscaping is 647 miles of extra romex, low voltage stranded landscape wiring, and the as-yet-to-be-adopted-by-industry CAT12 Ethernet cable with POE availability … just in case, mind you ….

 

[Dirk]

And hidden away amongst all that landscaping is 647 miles of extra romex, low voltage stranded landscape wiring, and the as-yet-to-be-adopted-by-industry CAT12 Ethernet cable with POE availability … just in case, mind you ….

That may be, but when the zombies come, I'll be ready. Can you say the same?

 

[JoyfulNoise]

I’ll be one of the Zombies …

 

[setsailsoon]

This thread gave me heart palpitations

When we Arizonans hear “flooded backyard” and “irrigation ran for a week”, we quickly look up our checking account balances because the next water bill is going to be more expensive than a week-long, all-inclusive trip to a Disney theme park

Agree with your assessment - definitely need a low level trigger AND a high-level alarm and shutoff.

I’ve never liked using irrigation components for pool controls. I realize they are designed for outdoor use but they can fail easily and they really need constant maintenance (at least mine always did when I had an irrigation system … I don’t irrigate anymore). You can’t see the overflow basin easily everyday and so that makes it an “out of sight/out of mind” problem. You might consider either installing a cheap mirror to reflect the basin towards you so you can throw some eyes on it OR install another cheap security camera to be able to do a level check occasionally. I have a similar problem as my equipment pad is out of sight. So unless I force myself to do a daily stroll over there, things can (and have) gone be unnoticed.

Hope the tannins clear out soon. With so much water overflowing the basin, you may need to do a detailed water analysis to see how much dilution has affected your stabilizer and salt levels.

Yep this would have been expensive if I had to pay more than pumping costs. The part that actually caused the problem was me, myself and I. Can't even blame this on the switch. I had it mounted on the end of a piece of PVC pipe that was just hanging over the edge at one end. With all the rain and wind we had that week it shifted and the level float on the switch jammed. I agree on irrigation parts for pools, it just seems OK for fill water since that comes from the irrigation well pump anyway. Don't know why but those irrigation valves seem to work like champs even with my aweful well water... wish I could say the same for my softener control heads. I think I'm going to have to put both of them on an annual replace schedule. Will disassemble the old one each year, soak in CLR and replace all the close tolerance parts so it's ready to be reinstalled next year.

The mirror is a great idea! I have a security camera that just can't quite see the basin and a mirror or remote camera would be easy to set up!

The tannins actually clear up pretty quickly as you predicted a long time ago. Took me a little while to realize this was tannins and not algae even though I had experience this during the first fill... you'd think I'd remember things like that!

My power bill will go up for this and your are absolutely right, that wasn't my only loss. I also I lost 2/3 of my salt and CYA. What a mess! Luckily we had so much rain it all just ran off into the storm drains that go to lakes and eventually overflow to the ocean when we have enough. Hope I can get all this fixed right before I need to do any more week long times away. Once I get into stable operation well water is turning out to work well. I'm adding about 40-80 gal per day due to evaporation across the 750+ sq ft surface area. Wind drives a lot of the variability. Adding well water as make up at 300 ppm seems to be reaching equilibrium above 50 ppm TA which works well. I was just getting to equilibrium for the first time when the week of overflow happened.

Learning as I go with this pool and I'm enjoying every minute of it!

Chris

 

[setsailsoon]

Oh man... Tough lesson there. Shoulda hazop'd the pool systems.

Hopefully no damage to the irrigation pump/well.

I've said it in your build thread but I'll say it again here... the pool looks freaking amazing! Love the picture window enclosure and what it does for the view!

--Jeff

Yep and LOPA follow up. The pump is an example of the value in buying good quality for a little more $. I bought it used from a well digging company since it supplied all my water during construction and had just been rebuilt. Construction is very rough service. Turns out it's a decades old Gould pump and even though it got heavily abused during construction I just left it on the irrigation well. I have a different well for the house water supply. Before rainy season is over I'll get it rebuilt by my pump local pump just to avoid problems. I have a temp tie-in to run the irrigation off my house pump for emergencies. Nothing like redundency for water supply!

Chris

 

[setsailsoon]

Lessons learned and shared=well done!

Robin and I did good on that picture window

You did indeed! It's a gorgeous feature that everybody notices.

 

[setsailsoon]

Very important Design Parameter

Here's another thing I learned about. There's an important ratio to keep in mind for infinity pools, zero edge or conventional skimmer designs. @JamesW actually went through this in one of his very helpful design calculations posts that helped me change quite a few design aspects and yielded a much more operable pool. That's the ratio of the pool surface area to basin (some call it trough) area. In my case it's ~12. So one inch of water in the pool equals 12" in the basin. It also works the other way. .25" in the pool (say for evaporation) will drop the basin level 3" (in one day!). You want to keep the level low in the basin so you have a lot of room for instantaneous 4 people jumping in the pool but if I go too conservative on this to say 6" I only have 2 days of evaporation when the basin is in manual level control. Even more likely during rainy season around here is let's say we get an inch of rain (this happens several days per week around here). That's 12 inch in the basin. I've got a pretty large basin (3'X2' and 36" deep). There's an overflow 6" from the top so that's 30" working range. If min level is 6" then I have only 24" to work with. I was real concerned during design that I needed to contain the water when 5 people jumped in to the pool at once. Two people jumping in the pool is only a little over 1" in the basin. But one normal rainy season day in S Florida is 12" in the basin... good thing I was conservative in the design of my first infinity pool!

If you end up with a zero edge in addition to the infinity edge this means the pool is full all the way to the pool gutters most of the time. On my pool that adds a foot to the width and a foot to the length. Since I have a 10X10 spa on one end and a 10X10 sun deck on the other my surface increases by 200 sq ft. Not insignificant for basin calculations!

Lots to learn with the first design and build of anything. There's a lot more of this but this aspect alone easily illustrates the importance of experience if you're selecting a builder for this kind of pool.

Chris

 

[Dirk]

What a great post. (And where does @JamesW come up with all his calc's!?!)

I'm sure people looking to build this type of pool have no idea what they're getting into. And the most important take away, IMO, is for them to make darn sure their builder understands, ahead of time, the physics of such a pool. I wonder what percentage do...

My "non-infinity" pool has about a 6-day evaporation buffer, mid-summer (if my auto-leveler failed). Though until I read your post I never thought of that in those terms. A two-day buffer barely covers a weekend away. This alone is something that should be well understood ahead of building an infinity pool.

 

[Dirk]

I gotta ask...

I'm just now finishing up recovering my yard and pool from my Fourth of July party (but still have one last chair to repair!!). The water clarity of the pool during the party was really something, something dismal, that is. Between my OCD and TFP, I can't go swimming at my own pool party! I digress. There was easily 20 people at a time in my pool a few times that day. Are infinity pool owners unable to accommodate that many in their pools?

If so, that's certainly something else that should be known ahead of building such a pool.

TFP should consider a Wiki article about the trials and tribulations of an infinity pool (if there isn't one already). Hey, lookie there, I just nominated you to write it!!

 

[JamesW]

Are infinity pool owners unable to accommodate that many in their pools?

It depends on the trough size, weir length and the flow rate.

The higher the flow rate, the more extra water is held in the pool.

If the trough is undersized for the number of people, you can increase the flow, which raises the water level in the pool, but that can risk the trough running dry, so get the trough sized correctly.

 

[setsailsoon]

I gotta ask...

I'm just now finishing up recovering my yard and pool from my Fourth of July party (but still have one last chair to repair!!). The water clarity of the pool during the party was really something, something dismal, that is. Between my OCD and TFP, I can't go swimming at my own pool party! I digress. There was easily 20 people at a time in my pool a few times that day. Are infinity pool owners unable to accommodate that many in their pools?

If so, that's certainly something else that should be known ahead of building such a pool.

TFP should consider a Wiki article about the trials and tribulations of an infinity pool (if there isn't one already). Hey, lookie there, I just nominated you to write it!!

20 people is roughly 450 gal. In my case the answer is yes because there's another important number - gal/in of basin. In my case it's 42. So that's 450/42=10.7". I have 24" to play with 36 total with 6" below top and 6" above bottom for usable range. In most cases this isn't hard to do and there are ways around it for installations with limited basin space. Of course each pool is unique. An excursion once a year for that big party that causes some overflow isn't usually that bad. But designs so bad that they flood a patio or fire pit anytime somebody enters the pool do happen because it wasn't designed properly... and sadly not all infinity pool designers have the good fortune to consult with TFP experts like we do!

Chris

PS It was kind of a tough slog at times to push through the build but boy was it worth it. On my way out now for a Sunday evening dip!!