Rainwater management solution for gutter & balance tank

[Bluejean]

I am making it up as I go with 2 DIY poured -concrete spill over pools...

I have already cast the concrete for a small indoor knife-edge pool, with gravity fed balance tank below. It went well, so I starting the concrete work for a similar exterior main pool.

It occured to me that I have not provided a robust solution for managing rainwater (as it is not a relevant concern with the indoor pool). I did include an emergency spillover drain in the balance tank, but I'm not sure what to do to prevent a big storm from flooding my outdoor pool balance tank (located in a basement pool/mechanical room).

Is there a technique for preventing rainwater from overwhelming a gravity fed gutter system? I can imagine an actuated valve at he gutter drain, but thought this issue must have been addressed with a technique I'm not envisioning? Perhaps a default-closed valve that is opened only when the pumps are running? At present, I don't have protection from anything more than a 1-2" rain event other than my balance tank overflow drain.

thank you for any guidance you might have!

 

[PoolStored]

Pics of what you are constructing will help...

 

[setsailsoon]

I am making it up as I go with 2 DIY poured -concrete spill over pools...

I have already cast the concrete for a small indoor knife-edge pool, with gravity fed balance tank below. It went well, so I starting the concrete work for a similar exterior main pool.

It occured to me that I have not provided a robust solution for managing rainwater (as it is not a relevant concern with the indoor pool). I did include an emergency spillover drain in the balance tank, but I'm not sure what to do to prevent a big storm from flooding my outdoor pool balance tank (located in a basement pool/mechanical room).

Is there a technique for preventing rainwater from overwhelming a gravity fed gutter system? I can imagine an actuated valve at he gutter drain, but thought this issue must have been addressed with a technique I'm not envisioning? Perhaps a default-closed valve that is opened only when the pumps are running? At present, I don't have protection from anything more than a 1-2" rain event other than my balance tank overflow drain.

thank you for any guidance you might have!

Photo's and dimensions for the pool gutters and balance tank are needed to give specific advice. I have a 28000 gal pool with infinity edge in the back and zero (knife edge) on all the rest of the sides. Creates a stunning look for our sunsets here in Florida! I find restricting flow from the gutters to the overflow basin using manual valves is perfect for most flow regimes. Outside the gutter I have tiles that angle upward slightly so I can run with the gutters and pool completely full. The gutters and infinity edge become skimmers so you don't need a skimmer box. If you have gutters all round you can do the same thing. But you need to angle the tiles outside the gutters so you can overflow the pool and not have it dump all over your deck. Setting flows should be pretty easy so for each pump speed. The calcs. aren't hard to do and level tolerance is critical. +/- 1/8" inch is a minimum! Doing your design remember every person adds about 23 gal instantaneously! My pool is 28000 gal and the overflow basin is 2500 gal. Works fine. Even for our 5" gully washer rains in S Florida. No matter what the size you'll always want to run normal level in the overflow tank at it's minimum practical level.

I hope this helps.

Chris

 

[Bluejean]

Photo's and dimensions for the pool gutters and balance tank are needed to give specific advice. I have a 28000 gal pool with infinity edge in the back and zero (knife edge) on all the rest of the sides. Creates a stunning look for our sunsets here in Florida! I find restricting flow from the gutters to the overflow basin using manual valves is perfect for most flow regimes. Outside the gutter I have tiles that angle upward slightly so I can run with the gutters and pool completely full. The gutters and infinity edge become skimmers so you don't need a skimmer box. If you have gutters all round you can do the same thing. But you need to angle the tiles outside the gutters so you can overflow the pool and not have it dump all over your deck. Setting flows should be pretty easy so for each pump speed. The calcs. aren't hard to do and level tolerance is critical. +/- 1/8" inch is a minimum! Doing your design remember every person adds about 23 gal instantaneously! My pool is 28000 gal and the overflow basin is 2500 gal. Works fine. Even for our 5" gully washer rains in S Florida. No matter what the size you'll always want to run normal level in the overflow tank at it's minimum practical level.

I hope this helps.

Chris

Thank you! The pool looks great!

I don't have pics as it isn't built yet, and the final design is TBD. I'm building a ~2400g tank in an adjacent basement now (forming the walls this week). I expect the pool will be ~ 20-25k gallons, but a high surface area to volume ratio (thus my realization that rain might be a big issue). I was thinking of something on the scale of 50ft x 15 ft = 750sqft surface

It sounds like you are manually closing the drain from the gutter when a storm is expected? I can do this, but we are often away from the property for extended periods (it is an off-grid ranch). I suppose I could close a valve on the gutter drain, and install an overflow drain in the same gutter at a slightly higher level (so rising gutter volumes can be evacuated away in a rain storm.

We are in S. Texas so it doesn't rain often (but we had a 7.5" storm this spring for example). This would be an extra ~3000g filling the gutter and draining into the balance tank!

I could build the gutter to hold a pretty large volume (1500g easily for a 50ft linear edge). and this could act as an additional buffer?

 

[setsailsoon]

Thank you! The pool looks great!

I don't have pics as it isn't built yet, and the final design is TBD. I'm building a ~2400g tank in an adjacent basement now (forming the walls this week). I expect the pool will be ~ 20-25k gallons, but a high surface area to volume ratio (thus my realization that rain might be a big issue). I was thinking of something on the scale of 50ft x 15 ft = 750sqft surface

It sounds like you are manually closing the drain from the gutter when a storm is expected? I can do this, but we are often away from the property for extended periods (it is an off-grid ranch). I suppose I could close a valve on the gutter drain, and install an overflow drain in the same gutter at a slightly higher level (so rising gutter volumes can be evacuated away in a rain storm.

We are in S. Texas so it doesn't rain often (but we had a 7.5" storm this spring for example). This would be an extra ~3000g filling the gutter and draining into the balance tank!

I could build the gutter to hold a pretty large volume (1500g easily for a 50ft linear edge). and this could act as an additional buffer?

High surface area just impacts the size of the overflow tank because inches per sq ft impacts the surge volume that will needed to avoid overflow. It still eventually needs to be disposed of just like a traditional pool. There's only so much that you can deal with. My evaporation rate is about 80 gal per day. So when we get a gully washer my overflow basin level increases. So the sizing of the tank just is determined by one or more of 3 criteria:

• How much surge to you want to be able to hold for when people enter the pool? I can easily hold 5+ people (assume ~23 gal/person)
• How much rain surge you want to hold before overflowing
• Minimum surge level to be sure you don't suck the basin dry when pump starts and gutters fill up (water in transit)

In my case I sized the basin for max people entering at the same time. Didn't want to be spilling water out the basin each time we had a lot of people over. But don't really care if that happens several times per year when we get our gully washers. And no attempt at all was made for storms... just not practical at all. I can hold up about a 6" rain with this sizing because I have an enclosure that causes some rain to run off the outside. If we don't get a lot more rain it will run off at 80 gal per day. So bottom line is during storm season I overflow the basin through an overflow line near the top fairly frequently. But when you think about it all pools have this issue if they use any kind of "close to constant" level control. The difference with a surge tank is you can have additional surge.

I don't really have any surge volume in the gutters since I run them full all the time for that glass smooth full appearance. It seems like your design concept is different and I'm not sure I understand it. Not saying it won't work, just I don't think I understand what the concept is. My gutters are only 2"X3" which gives me only .31 gal/ft. I have about 128' of perimeter gutter which equals roughly 40 gal total. I also sized the outer tile slope to have plenty elevation such that I could accommodate ~5/16" rise over the infinity wall which takes a flow rate over 250 gpm and required the 5 hp commercial Pentair pump.

I hope this is helpful.

Chris

 

[Bluejean]

High surface area just impacts the size of the overflow tank because inches per sq ft impacts the surge volume that will needed to avoid overflow. It still eventually needs to be disposed of just like a traditional pool. There's only so much that you can deal with. My evaporation rate is about 80 gal per day. So when we get a gully washer my overflow basin level increases. So the sizing of the tank just is determined by one or more of 3 criteria:

• How much surge to you want to be able to hold for when people enter the pool? I can easily hold 5+ people (assume ~23 gal/person)
• How much rain surge you want to hold before overflowing
• Minimum surge level to be sure you don't suck the basin dry when pump starts and gutters fill up (water in transit)

In my case I sized the basin for max people entering at the same time. Didn't want to be spilling water out the basin each time we had a lot of people over. But don't really care if that happens several times per year when we get our gully washers. And no attempt at all was made for storms... just not practical at all. I can hold up about a 6" rain with this sizing because I have an enclosure that causes some rain to run off the outside. If we don't get a lot more rain it will run off at 80 gal per day. So bottom line is during storm season I overflow the basin through an overflow line near the top fairly frequently. But when you think about it all pools have this issue if they use any kind of "close to constant" level control. The difference with a surge tank is you can have additional surge.

I don't really have any surge volume in the gutters since I run them full all the time for that glass smooth full appearance. It seems like your design concept is different and I'm not sure I understand it. Not saying it won't work, just I don't think I understand what the concept is. My gutters are only 2"X3" which gives me only .31 gal/ft. I have about 128' of perimeter gutter which equals roughly 40 gal total. I also sized the outer tile slope to have plenty elevation such that I could accommodate ~5/16" rise over the infinity wall which takes a flow rate over 250 gpm and required the 5 hp commercial Pentair pump.

I hope this is helpful.

Chris

I am circling back after considering more details…

I am preparing to pour the concrete for this exterior pool in the coming days (cast-place, not shot). One element I didn’t adequately consider was pressure-side piping. I had assumed 2”, but realize now larger PVC may be optimal.

Here is a sketch of our pool layout:
Spillover on one side, with gutter flowing to 2500g balance tank (mechanical room).

 

[Bluejean]

I was planning to use 4" PVC to plumb the supply/pressure jets (as I have a lot on hand). I would prefer not to use floor drains and will provision means for draining the pool with a simple garbage pump. The gutter will not have drains as it will simply flow into the balance tank via gravity.

Can you advise what size pipes/fittings to cast into the concrete walls? I assume it is normal practice to reduce from larger pipe for the wall jets?

Is there a benefit to plumbing two pump 'systems'? I was thinking of one for pulling from the tank & pushing water over the spillover and another for convention circulation/filtration when the spillover is not being used. Each would be filtered.

This project is completely off-grid (solar)

thank you !!

 

[setsailsoon]

You really can't do a "rule of thumb design" for pipe sizing. Need to do a proper layout and get elevations from the pad to the water level in the basin and pool so you can get system pressure drop. If you're in that much of a hurry and you can make the assumption my pool is a little bigger than you can do what I did. For the basin I had 3" drains that tied to a 4" suction line back to the pump. I also had 11' of head difference to the suction of my pump so it's unlikely you'd need more. My average piping runs were about 75'. It really doesn't take that much effort to get a sketch with dimensions for all the suction and discharge pipe with elevations. Then you can do this right and avoid digging stuff up. If you had a building department they'd require it. If you can provide this level of detail we have several fluid mechanics experts that will do this for you pretty quick. @JamesW , do you have time to help him? @JamesW is a true expert in this stuff - it's pretty unusual to find a technical expert that's also got practical things right like check valve placement. Be careful how you engage him and Matt (@JoyfulNoise) or they'll get into one of their dialogs that only they can follow. A lot of people on here say you don't need a drain and I agree but I put one in anyway. More of a personal preference for me than a clearly supportable requirement.

I hope this helps.

Chris

 

[Bluejean]

You really can't do a "rule of thumb design" for pipe sizing. Need to do a proper layout and get elevations from the pad to the water level in the basin and pool so you can get system pressure drop. If you're in that much of a hurry and you can make the assumption my pool is a little bigger than you can do what I did. For the basin I had 3" drains that tied to a 4" suction line back to the pump. I also had 11' of head difference to the suction of my pump so it's unlikely you'd need more. My average piping runs were about 75'. It really doesn't take that much effort to get a sketch with dimensions for all the suction and discharge pipe with elevations. Then you can do this right and avoid digging stuff up. If you had a building department they'd require it. If you can provide this level of detail we have several fluid mechanics experts that will do this for you pretty quick. @JamesW , do you have time to help him? @JamesW is a true expert in this stuff - it's pretty unusual to find a technical expert that's also got practical things right like check valve placement. Be careful how you engage him and Matt (@JoyfulNoise) or they'll get into one of their dialogs that only they can follow. A lot of people on here say you don't need a drain and I agree but I put one in anyway. More of a personal preference for me than a clearly supportable requirement.

I hope this helps.

Chris

Thank you!

I actually had all the rebar tied today and plan to pour the pool floor (slab) on Wednesday. I will put a single gravity drain in one corner to assist with manual draining. Pool is built on a cliff so I have lots of footer drain piping I will tie into, leading to a ale below.

The floor of the balance tank is -12ft below the water surface, but is only 3 feet away horizontally. I will not have suction lines in the gutter system - water will return to the surge tank by gravity. My primary pump would sit directly above the tank, sucking ~6ft vertical and then pushing into a series of pool wall mounted jets (another ~3ft of rise).

My assumption was that I could build a simple horizontal manifold with 4” pvc, reducing to 2” when penetrating the pool walls. The majority of the jets would be along a 50ft straight pool wall, with the pump located near the center line. Max run of 25-30ft from the pump location.

Separate from this gravity return system, I could install a duplicate, conventional circulating system, with suction & pressure in the walls… I would connect this system to the heat pump and run regularly, leaving the larger overflow pump to induce the weir wall spillover.

Is this in-line with conventional wisdom?

Thank you!

 

[PoolStored]

Pool is built on a cliff

 

[Bluejean]

After the pool is poured, we can remove the cliff overbuild and work our way out (which is why I needed to pour the pool now)

 

[PoolStored]

Where is the pool in this picture?...you gotta show us more angles and explain what we are looking at, this is wild!

 

[Newdude]

Where is the pool in this picture

Per the sketch in post 6, it's the trapezoid.

+1 this is wild all over.

 

[Bluejean]

Where is the pool in this picture?...you gotta show us more angles and explain what we are looking at, this is wild!

Haha - too many things going on! Yes, the trapezoid is the pool. Finished the rebar last evening - it’s a bit bigger based on where I set the corners. About 1200sqft it appears.

The open basement next to the rebar will house the tank. Exterior patio will cover this element. A pool house is dig into the cliff on the opposite end. Largely due to my lack of drawings, it’s taken a while to get to this point, but moving faster now as dried concrete keeps me from changing my mind too much!

 

[Bluejean]

 

[setsailsoon]

Thank you!

I actually had all the rebar tied today and plan to pour the pool floor (slab) on Wednesday. I will put a single gravity drain in one corner to assist with manual draining. Pool is built on a cliff so I have lots of footer drain piping I will tie into, leading to a ale below.

The floor of the balance tank is -12ft below the water surface, but is only 3 feet away horizontally. I will not have suction lines in the gutter system - water will return to the surge tank by gravity. My primary pump would sit directly above the tank, sucking ~6ft vertical and then pushing into a series of pool wall mounted jets (another ~3ft of rise).

My assumption was that I could build a simple horizontal manifold with 4” pvc, reducing to 2” when penetrating the pool walls. The majority of the jets would be along a 50ft straight pool wall, with the pump located near the center line. Max run of 25-30ft from the pump location.

Separate from this gravity return system, I could install a duplicate, conventional circulating system, with suction & pressure in the walls… I would connect this system to the heat pump and run regularly, leaving the larger overflow pump to induce the weir wall spillover.

Is this in-line with conventional wisdom?

Thank you!

I actually had all the rebar tied today and plan to pour the pool floor (slab) on Wednesday. I will put a single gravity drain in one corner to assist with manual draining. Pool is built on a cliff so I have lots of footer drain piping I will tie into, leading to a ale below. I'm not sure what this looks like. Just make sure you put the drain at the lowest point in the pool. Manual draining for the gutters is normal. You may want to add a piece of pipe at the end where the gutters flow into the basin. This gives you the ability to put a valve for flow restriction. Make sure you have the tile outside of the gutter sloped up so pool water doesn't spill out onto the deck. In my case I angled it up ~3/4" so I can raise the water level of the pool enough when going from no flow to an aesthetically pleasing 3/8" to 1/2" and still allow for the practical limits of elevation control in the real world. Also, make sure all gutter and infinity walls top edge are very tightly controlled elevation all around the pool. My spec was +/- 1/8". It's hard to do this. You'll need at least a water tube level or better yet a zip level.

The floor of the balance tank is -12ft below the water surface, but is only 3 feet away horizontally. I will not have suction lines in the gutter system - water will return to the surge tank by gravity. My primary pump would sit directly above the tank, sucking ~6ft vertical and then pushing into a series of pool wall mounted jets (another ~3ft of rise). So is the tank where you handle the surge from people getting into the pool? If so you want to have the suction as low to the bottom as possible to give you the max surge capacity. But you don't want to run it dry and cause the pump to lose suction.

My assumption was that I could build a simple horizontal manifold with 4” pvc, reducing to 2” when penetrating the pool walls. The majority of the jets would be along a 50ft straight pool wall, with the pump located near the center line. Max run of 25-30ft from the pump location. I hate to sound like a broken record but I wouldn't assume anything about pipe sizes. They should be calculated. The number and placement of returns are important and easy to calculate the number. Placement is a little less a calculation and more just based on how you want water to mix and circulate. In general you want to avoid "dead spots" so chlorine gets to every part. Also some use floor returns along the bottom of the infinity wall. Return penetrations can be 1.5" or 2". There seemed to be a lot more choices for fitting style in 1.5" size that were readily available to me so I went with 1.5". Make sure there is at least 6" extra sticking inside the pool. You'll come back later and cut the pipe after plaster is applied. Make sure you have plenty of extra fittings when you do the plaster. It's easy for them to get broken. Hayward and CMP make a LOT of different styles.

I have both a deep end drain and drains in my overflow basin with valves to chose which is used. Most of the time I pull from the basin with the big pump and I use the filter pump to draw from bottom of the pool. Please do get some calculations done for the hydraulics. How much water height do you want over the infinity wall and how are you planning to control what goes in the gutters vs the infinity wall? This is very important for a pool that has both. It takes a surprising amount of water flow to give even .25" of water height. Your infinity wall didn't seem to be too long. Mine was 32' and drove me to a 5 hp commercial pump. I would have hated to guess the pump size and then have to buy another one and redo piping diameters.

I hope this is helpful.

Chris

 

[setsailsoon]

OK the photos and sketches are helping me understand the project. Couple of thoughts:

• This pool is going to be stunning! What are the other structures in the photo?
• You have a very long spillover. 60% longer than mine. You're gonna need a huge pump or two times mine to be safe. These things have a way of cascading through the design. For example, how many amps are available from the pool sub panel? You may need the next size up and this will require larger wires from the main breaker. In my case I was almost at the limit for residential power in standard FLP power drops with 400 amp service. They will go higher if needed but it can cause a lot of extra cost and time for approval.
• Your desired flow rates could be pushing 4" pipe on the suction side. The only way to tell is to get those hydraulic calcs done.

Looking back at your first post I'm not sure we answered some of your earlier questions:

"It occurred to me that I have not provided a robust solution for managing rainwater (as it is not a relevant concern with the indoor pool). I did include an emergency spillover drain in the balance tank, but I'm not sure what to do to prevent a big storm from flooding my outdoor pool balance tank (located in a basement pool/mechanical room).

Is there a technique for preventing rainwater from overwhelming a gravity fed gutter system? I can imagine an actuated valve at he gutter drain, but thought this issue must have been addressed with a technique I'm not envisioning? Perhaps a default-closed valve that is opened only when the pumps are running? At present, I don't have protection from anything more than a 1-2" rain event other than my balance tank overflow drain."

I spent a lot of time investigating how to deal with too much water from gully washer rains we get and the opposite when windy dry weather can consume a LOT of water due to evaporation. I designed and experimented with some very fancy electronic level sensors and custom designed controls using a Raspberry Pi and/or esp 32. At the end of the day I realized it just wasn't practical to design for storm season other than to be sure my open top basin could overflow down the back of the property and I included an over-flow pipe near the top of the basin. The ratio of the pool surface area to the basin area became a very important number in my case it's about 10 (thank you @JamesW for pointing this out early to me). So 1" of rain became 10" in the overflow basin. My basin is 36" total depth so a 2" rain uses 20" of the basin range. When you subtract some for min level and the overflow pipe I have about 28" to work with. We get 6" of rain within 6 hours several times per year from locally heavy thunderstorms so there's no way for me to manage this much water without going to extraordinary and unaffordable means. Also with my zero edge design (and yours) the pool is virtually full all the time. So why worry about the basin overflowing? The only impact is a loss of salt and other chemicals that can be corrected after the storm. So the pool will function with no issues over 95% of the time and risks overflow a few days per year. No big deal.

Another thing to think about is the opposite condition where water loss needs to be added. We experience 40 to 80 gallons of water evaporation in normal fluctuations of wind speed every week. Temperature and humidity affect water loss but wind speed has much more effect. With my big 5 HP pump for infinity wall flow I don't want to suck the basin dry. Bad for the pump and tough to have to re-prime it all the time. By far the easiest way to control minimum level was to install a watering trough float style level fill nozzle near the bottom of the basin. Works like a charm! Can't remember who suggested this but it's always important to remember simple solutions are almost always the best. I have it tied in to the discharge of my irrigation well pump before the sprinkler valves. It usually only runs for a few minutes.

I hope this helps.

Chris