Putting in an overflow at the pad... how to?

[rtilghman]

So, when I put in my pool the PB never brought up the idea of an overflow system, and after some crazy rains here in Austin (and some overflow situations) I'm thinking of putting in an overflow valve. Looking to get some sage advice from folks on my plan.

The plan is to put the overflow at the pad. Since my pool sits above above the pad (about 3'?), I'm thinking I just need to cut into the return line before the pump and install a "U" that goes up, turns at the appropriate level (just below the coping), and then take it back down and tie it into the massive drain system I installed with the pool (6" pipe down to the street). I'll probably use a laser level to make sure I get the level right, and use a 3/4" pipe (I don't think I'll ever have enough flow to need anything bigger, but maybe I'll just use 1").

The questions and concerns:

1) Do I need to worry about pressure or closing off the overflow in some way? Not sure how I would do this given the fact that it has to be gravity driven... I'm assuming gravity and suction will prevent water from pushing through the overflow when the pump is on or off?

2) Is there a best place to put the overflow other than just before pump?

3) Optimal pipe size? Something else I'm missing?

Thanks!

Rick

 

[tim5055]

What you are calling the "return" side (before the pump) is actually the suction side, meaning the pump is sucking the water out of the pool. After the pump is the return side as in water returning to the pool.

I don't know of any way to plumb an overflow into the piping. Any opening on the suction side is going to cause the pump to loose prime and any opening on the return side will become a fountain.

An overflow is a passive path for water to flow out of the pool when it reaches a specific level.

 

[Jimrahbe]

I can see this working when the pump is off, but as soon as you turn the pump on I think it will just start sucking air through your "U" pipe. I guess you could put a one way valve in the "U" pipe that would allow the excess water to enter your drain system, but prevent air from coming the other way. Of course this would be the first place to look next time your pump won't prime.

Sounds like an interesting project. Let us know how it turns out.

*** keep in mind that I have little water flow expertise, so you might want to wait for others to comment.

Jim R.

 

[pooldv]

Seems like the best thing to do is to get a big concrete drill and drill a 2" hole through the pool wall at the waterline, retrofit a 2" pipe through the wall, install an overflow grate and plumb it to your drainage system.

Like this, http://www.pentairpool.com/products/white-goods-gutter-drains-65.htm

Also, you might be able to retrofit an overflow line into a skimmer or an autofill basin.

 

[banditig]

Your equipment is 3 feet below water line? That is almost an above ground pool like setup. I would worry about the siphoning situation, especially without an air gap at the same level. Why not just put manual shut off valve at a tee the correct level. Turn valve on when pump is off, but keep eye out and don't forget about it before you turn the pump back on.

 

[Divin Dave]

Interesting situation.

If you have a filter with a multiport valve, you can put it on waste and pump water out using the pump without having do anything else.

Putting a drain pipe on the suction line with a valve in front of the pump "might" work. The valve would need to be a really good one though so the pump wouldnt suck air when it's closed.

One on the return side would require a valve too.

Another alternative is install a 3 way valve between pump and filter and route that pipe to the drain. If you have a cartridge filter, this could do double duty in that you will be able to vacuum to waste if you need to.
This method may likely require turning the pump on and off when needed.

It seems in any case though, you're going to have to be active in controlling the water level by means of turning the valve on and off.

 

[atttech-2]

building on pooldv's idea depending on your decking situation you could drill a whole into your skimmer or auto fill if you have one at the max level you want the water. I would think 3/4 line would be plenty if it was in the auto fill since there would not be any leaves to block it, if it was in the skimmer you would need to go bigger or put a screen over it. my deck is only 18 inch at the auto fill so this is what I have been thinking about just waiting to see if it is even needed since I live in the desert some call California

 

[AUSpool]

I don't think cutting in to a suction or return line is a good idea for an overflow unless it's for a valve to pump water to waste but that requires manual operation. But that's exactly what I did, I had the same problem with lots of rain and no overflow. It always needed draining during a storm and our only method was draining to waste and playing with power during a rain event is never a good idea.

Adding an overflow to an existing skimmer box is probably the best solution but I couldn't tap into mine and I thought it was to hard to core drill my concrete pool. My pool has three returns and I have access to my return line from under the pool deck. I was able to tap into the return line just before the last return and using a series of valves can now use the last return to the pool as an overflow or just a return. In the rainy season the last return is an overflow and the rest of the year it's just a return. Be careful to install a syphon break if needed or the overflow could turn into a syphon and drain the pool.

 

[rtilghman]

I can see this working when the pump is off, but as soon as you turn the pump on I think it will just start sucking air through your "U" pipe. I guess you could put a one way valve in the "U" pipe that would allow the excess water to enter your drain system, but prevent air from coming the other way. Of course this would be the first place to look next time your pump won't prime.

Sounds like an interesting project. Let us know how it turns out.

*** keep in mind that I have little water flow expertise, so you might want to wait for others to comment.

Jim R.

Great point about the pressure issues... I hadn't really thought about the suction component of the overflow. Yeah, I can probably solve that pretty easily with a one way valve. I've already got two on the pad based filler system I set-up... irrigation main is hooked into pad intake side, with two ball valves to control filling... planning to replace the manual stuff with a wireless system at some point in the future, which is one reason this overflow is critical.

The only question is whether the one way valve will be "easy" enough on the push side for the overfill to work? What I mean is when the pool overflows the water will clearly rise to crest in the pipe, but will there be enough pressure from gravity alone to push through it? As I remember the spring in those valves is intentionally light (since suction and/or pressure from the other side handles the "sealing" needs), but until the overflow fills ("true" overflow) there won't be a lot of pressure on the valve door.

Thoughts? I guess it's just a question of mounting the overflow "u" at a level that's on the low side of my target... meaning positioning the top end of the valve and pipe so that the top half is in my target zone.

I'll probably also put a ball valve on the back side so I can truly close off the line in the event the one way valve fails.

Interested in any additional insights or guidance you or others have! Maybe someone who's done something like this before?

Thanks,
Rick

 

[rtilghman]

Sorry, just saw all these replies that didn't show up before... wierd.

Drilling is a non-starter... I'm not looking to mess with the pool shell, and getting through my deck would involve too much horizontal drilling through concrete and/or destroying my lueder deck. If I'm going to get this to work it has to be at the pad.

Yes, my pad is about 2-3' below the pools top level. We live on a fairly flat part of a hill/incline, with the level rising from street to back yard. The pool is against the back (L running from back fence to house lengthwise), and the pad is beside the house. The back end of the pool is basically level with ground, front side is retaining wall/planter/steps). It makes sense and looks great, definitely not to be mistaken for an above ground pool.

To all the comments about manual control, not what I'm going for. I can't be going out there every time I want to drain it, and that wouldn't solve the issue of emergency overflow management (like when we have a crazy 4-5" rain overnight). I have an alternate idea for manual drain control that may or may not tie into this... my plan was to lead a line out of the filter's tap into my large 6" drainage system, though I can just as easily tie a bypass into the overflow system.

To my previous comment, is there a reason an overflow with a check valve wouldn't work? Something like this:


Thanks,
Rick

 

[azjoshers79]

Or you can buy a submersible pump and a hose for 50 bucks and your good to go.


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[rtilghman]

Or you can buy a submersible pump and a hose for 50 bucks and your good to go.


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Having all that gear sitting in my pool would entirely defeat the purpose, and would also look like garbage.

rt

 

[azjoshers79]

The pump is not in your pool all the time, if there is a large rain storm you just put the pump in and bring the water level down. I did this for 7 years on my previous pool and will do the same with my new pool. And Arizona can get monster rainstorms during monsoon season.


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[azjoshers79]

Just drop this in after a storm, only takes a few minutes to bring the water level back down. It's just an affordable solution if you pool wasn't built with an overflow.


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[AUSpool]

Sorry, just saw all these replies that didn't show up before... wierd.

Drilling is a non-starter... I'm not looking to mess with the pool shell, and getting through my deck would involve too much horizontal drilling through concrete and/or destroying my lueder deck. If I'm going to get this to work it has to be at the pad.

Yes, my pad is about 2-3' below the pools top level. We live on a fairly flat part of a hill/incline, with the level rising from street to back yard. The pool is against the back (L running from back fence to house lengthwise), and the pad is beside the house. The back end of the pool is basically level with ground, front side is retaining wall/planter/steps). It makes sense and looks great, definitely not to be mistaken for an above ground pool.

To all the comments about manual control, not what I'm going for. I can't be going out there every time I want to drain it, and that wouldn't solve the issue of emergency overflow management (like when we have a crazy 4-5" rain overnight). I have an alternate idea for manual drain control that may or may not tie into this... my plan was to lead a line out of the filter's tap into my large 6" drainage system, though I can just as easily tie a bypass into the overflow system.

To my previous comment, is there a reason an overflow with a check valve wouldn't work? Something like this:
View attachment 44084

Thanks,
Rick

Geday Rick,

I think your plan may work but I would install any new plumbing inside a pair of barrel unions just in case it all turns pair shaped it would be easy to reverse it.

Since your pump is below water level I don't think you will have any prime issues.

Most of those non returns have springs which can be kind of tight, maybe to tight for your application. There are 'flapper' or springless ones that look similar but after just installing four Jandy non-returns I think one of those in the horizontal with the spring removed would be you best bet.

3/4 and 1" will be too small, use 11/2" minimum. I made mine out of 11/2" and it works but I haven't been able to test it in a big down pour yet, may need to upsize to 2" or even 21/2" to be safe. Your essentionally creating a weir within a horizontal pipe, I used 1" pipe in the vertical to create overflows or weirs in a multi tank aquaculture system which was not enough for much smaller flow rates.

It is absolutely essential that you provide a syphon break to prevent the overflow becoming a full syphon and draining your entire pool! Another reason to use larger pipe, to provide separation between the water level in the pipe and the syphon break otherwise the syphon break will just become a Venturi suck air and water until a good portion of your pool has drained!

The syphon break must go from the top of the U to well above the water line otherwise your back to a full syphon and disaster.

Another potential problem of sharing the suction line where the pump has priority over the overflow is that overflow won't work until the pump shuts off and if it starts when the pool is already overflowing it may start as a full syphon and drain a good portion of the pool. The overflow really needs to start as the water level first starts to rise. A rain sensor and contactor to shut the pump off when it rains might work.

Good luck with it, Steve.

 

[rtilghman]

Geday Rick,

I think your plan may work but I would install any new plumbing inside a pair of barrel unions just in case it all turns pair shaped it would be easy to reverse it.

Since your pump is below water level I don't think you will have any prime issues.

Most of those non returns have springs which can be kind of tight, maybe to tight for your application. There are 'flapper' or springless ones that look similar but after just installing four Jandy non-returns I think one of those in the horizontal with the spring removed would be you best bet.

3/4 and 1" will be too small, use 11/2" minimum. I made mine out of 11/2" and it works but I haven't been able to test it in a big down pour yet, may need to upsize to 2" or even 21/2" to be safe. Your essentionally creating a weir within a horizontal pipe, I used 1" pipe in the vertical to create overflows or weirs in a multi tank aquaculture system which was not enough for much smaller flow rates.

It is absolutely essential that you provide a syphon break to prevent the overflow becoming a full syphon and draining your entire pool! Another reason to use larger pipe, to provide separation between the water level in the pipe and the syphon break otherwise the syphon break will just become a Venturi suck air and water until a good portion of your pool has drained!

The syphon break must go from the top of the U to well above the water line otherwise your back to a full syphon and disaster.

Another potential problem of sharing the suction line where the pump has priority over the overflow is that overflow won't work until the pump shuts off and if it starts when the pool is already overflowing it may start as a full syphon and drain a good portion of the pool. The overflow really needs to start as the water level first starts to rise. A rain sensor and contactor to shut the pump off when it rains might work.

Good luck with it, Steve.

AWESOME post, thanks Steve! Funny, I'd never heard of a "weir" before... not that I know that much about spillways or flow mechanics, but I'd just never come across the term. Yes, that's definitely what I'm looking to create.

So I don't know that much about Siphons (aside from the basics), but doing some research I'm a little confused why this would be an issue. Maybe you can elaborate?

To provide some additional insight, my intake runs from three spots; skimmer, pool drain, and spa drain. If we call the pool water level "0", the three pipes basically run at about -3, then go vertical at the pad, merging into a single intake at the pump that sits around -1/-2 (there's an automated switchover between the spa and the 2 pool lines, with intake depending on active mode... spa or pool). The overflow will either be installed on one of the vertical pool return lines or in the lateral pipe that runs from the three to the pump, with the top edge/turn of the overflow "U" even with the target level. The overflow will include both a manual ball valve (maybe two, for emergencies) and the check/one way valve.

As I understand it a siphon is a combination of gravity and air pressure, with the water looking for equilibrium. Contrary to popular perception, a siphon isn't a perpetual motion machine (i.e., it won't keep running once it starts until the source is empty), but will stop when equilibrium is achieved. Given that air pressure is basically equal when the pump is off, equilibrium would seem to be when the level of the source (pool) equals or drop s below the top edge of the overflow pipe.

Is this correct? What am I missing? And why do I need the siphon break in the top of the overflow U? Wouldn't the level + ambient air pressure in the pipe + spring pressure of the one way valve be enough to counter the drain? Or is the gravity/force of all that pool water enough to push water uphill? Sorry if these are basic questions, just want to make sure I understand.

The insights about the issues when the pump is operational are great... hadn't thought about that at all. My pump runs from 8-10am (100%) and from 12-5pm (50%), so it doesn't leave a lot of time during daylight hours. However, assuming the pool is able to level itself with any 2 hour window (via the overflow system) I don't think we'd ever see 5+ inches in 5 hours which is what it would take for the pool to crest during the longest stretch (coping = 2" thick, optimal level = 3" below coping). So, it would seem like I can survive without a rain sensor, though long term some kind of udometer would definitely be cool.

Interested in any additional thoughts you have on the questions. Thanks SO MUCH for the reply, really great stuff man.

Best,
Rick

 

[AUSpool]

I had never looked up the definition of a syphon before, I've just played with them for years with fish tanks. The wiki has a nice definition with the little picture below and it's easy to think that if you lower the U tube to the starting level of the source reservoir then the syphon will only drain down to that level but no... it will drain down to the bottom of the syphon tube in the source reservoir providing that the other end of the syphon is lower.


For your application that would be the bottom of the skimmer opening in the pool or the main bottom drain if it's connected to that. So we don't confuse each other there are two sides to pool plumbing, the suction lines which is every thing between the pool or spa and the pump, and the return, which is everything after the pump.


Your overflow will not work on the return side, you'll be pumping water to waste. The overflow and non return valve will only work on the suction side of the pump, connected to the skimmer which isn't as low as the main drain.


I don't think a spring type non return will work, it will provide to much resistance to opening in the overflow direction.


The weir will be the horizontal section of the top of the U and the bottom of that part of the plumbing will dictate the level that the pool will drain to. The reservation I have with this is that either weir / overflow or syphon will not work when the pump is running and if you have a rain event and the pool level rises up above the top of the U a syphon will start when the pump stops and the pool can drain down to the skimmer or bottom drain if it is connected to that.


A syphon break or breather hole in the top of the U will to some degree prevent a syphon from starting. If the pool water level is above the U when pump shuts off a syphon will start and the syphon break will be a venturi sucking air into syphon. The syphon will continue until the flow slows and the syphon break can its job. A syphon will start more easier in a spiller diameter pipe than larger.





Instead of a U how about connecting your line from the skimmer via a non return to a secondary container or tank with a stand pipe type overflow and avoid any chance of a syphon. The secondary tank would have the same water level as the pool. The stand pipe needs to be at least a 2" pipe but you can go through the side or bottom of the tank and connect to your drain with 1" pipe. A very dodgy sketch but hopefully enough to get the idea.

 

[rtilghman]

I had never looked up the definition of a syphon before, I've just played with them for years with fish tanks. The wiki has a nice definition with the little picture below and it's easy to think that if you lower the U tube to the starting level of the source reservoir then the syphon will only drain down to that level but no... it will drain down to the bottom of the syphon tube in the source reservoir providing that the other end of the syphon is lower.


For your application that would be the bottom of the skimmer opening in the pool or the main bottom drain if it's connected to that. So we don't confuse each other there are two sides to pool plumbing, the suction lines which is every thing between the pool or spa and the pump, and the return, which is everything after the pump.


Your overflow will not work on the return side, you'll be pumping water to waste. The overflow and non return valve will only work on the suction side of the pump, connected to the skimmer which isn't as low as the main drain.


I don't think a spring type non return will work, it will provide to much resistance to opening in the overflow direction.


The weir will be the horizontal section of the top of the U and the bottom of that part of the plumbing will dictate the level that the pool will drain to. The reservation I have with this is that either weir / overflow or syphon will not work when the pump is running and if you have a rain event and the pool level rises up above the top of the U a syphon will start when the pump stops and the pool can drain down to the skimmer or bottom drain if it is connected to that.


A syphon break or breather hole in the top of the U will to some degree prevent a syphon from starting. If the pool water level is above the U when pump shuts off a syphon will start and the syphon break will be a venturi sucking air into syphon. The syphon will continue until the flow slows and the syphon break can its job. A syphon will start more easier in a spiller diameter pipe than larger.





Instead of a U how about connecting your line from the skimmer via a non return to a secondary container or tank with a stand pipe type overflow and avoid any chance of a syphon. The secondary tank would have the same water level as the pool. The stand pipe needs to be at least a 2" pipe but you can go through the side or bottom of the tank and connect to your drain with 1" pipe. A very dodgy sketch but hopefully enough to get the idea.

Okay, I get you, since I don't have a back-end on the overflow there's no "level" to provide the counter pressure necessary to push back on the siphon and equalize the force. Makes sense.

I still can't help thinking the siphon will "break" on it's own since the water in the overflow pipe will never fill the pipe (the way a hose or straw gets filled with a more typical siphon). Basically, assuming I use 2" PVC there will always be air in the upper and back side portions of the overflow pipe, so a suction/vacuum type situation is extremely unlikely. However, not necessarily worth the risk if the alternative is easy enough.

On that note, I like you're idea about incorporating some kind of interstitial holding tank. I think I can probably just change the elbow on the top of the skimmer return to a T and then put the whole rig on the outside, using a 4" pipe as the holding tank and another T as the kick-out for the overflow level. See the diagram below for a rough idea of what I mean.



The only question is where I put the one way valve to close the circuit when the pump is active. However, as I write this I think I just realized it has to be between the holding tank and the pool skimmer... it could be in the middle of the holding tank, but why buy a 4" check valve when a 2" one is cheaper. Thoughts?

To the concerns around not overflowing with the pump on, as I mentioned in my earlier response I'm not really concerned. The point here is to provide a passive overflow system that will handle most/all of my overflow needs without requiring me to do anything. Assuming it works the pool will typically be about 5" below the top of the coping, and my longest filter cycle is 5 hours. If we have a storm with enough rain that we're getting over an inch an hour for 5 hours AND it happens between 12pm and 5pm it'll be a big enough storm that I'll be on call for it.

I also already have a hose c0ck behind the pump that I use to drain water... with the pump on it's pressurized, so I can exhaust a lot of water quickly in a pinch. Right now I manually put the hose into one of the ground drains on my 6" pipe, but I'll probably install a c0ck on the backside of the overflow exhaust pipe and then run some short hosing between the two to make it more permanent.

Now I just need to figure out the lowest impact way to cut into my existing returns so I can install the modified parts. It's basically flush mounted Ts, elbows, and valves, so putting this in will probably require some wholesale replacements... ugh.

Very cool man, thanks again for the help. Let me know if you have any thoughts on the check valve or the rest of the set-up.

Best,
Rick

P.S. c0ck is not a curse word, thanks annoying nazi content filter.

 

[AUSpool]

I'm really worried we're not on the same page here Rick,

... to cut into my existing returns so I can install the modified parts.

The returns of a pools plumbing are behind the pump, from pump back to pool. A passive overflow device and a non return will not work in the return lines as passive overflow and return flow are heading in the same direction.

... change the elbow on the top of the skimmer return...

Again, are we talking about the return or suction side of the pump but more importantly any skimmer I've ever seen has the plumbing connection communing out of the bottom of the skimmer.

Okay, I get you, since I don't have a back-end on the overflow there's no "level" to provide the counter pressure necessary to push back on the siphon and equalize the force. Makes sense.


I still can't help thinking the siphon will "break" on it's own since the water in the overflow pipe will never fill the pipe (the way a hose or straw gets filled with a more typical siphon). Basically, assuming I use 2" PVC there will always be air in the upper and back side portions of the overflow pipe, so a suction/vacuum type situation is extremely unlikely. However, not necessarily worth the risk if the alternative is easy enough.

I think it's the other way around, I was assuming you would have a connection on the back end of the overflow or U and its this piece that provides the flow and suction to drive the syphon. A lot of your existing plumbing would make up the front und of a syphon including all the way to the bottom drain. Expect the unexpected, it's not just a rain event that can cause the possibility of a syphon, someone jumping in the pool would be enough to flood that section and suddenly your draining your pool to waste!


It sounds easy to swap out an elbow for a tee but in practice it can be quite tricky and once you start cutting into your existing plumbing it will never be the same again. You can't just swap one for another, you'll be swapping one for several and every extra fitting adds head pressure to the pump. If you cut into your existing plumbing it is flooded and all the water in the pool will drain out to that point.


My preference would be to provide a dedicated connection to the pool for a passive overflow but I don't see the point of going to all the trouble if you don't get enough rain to overflow your pool in an hour or two. Maybe it would be better to make a permanent connection from the valve you currently use to drain your pool to your 6" drain pipe. If I were you I would get the original pool builder back to 'quote' on your idea and get his ideas or advise.


Non returns do fail and it can damage the pump and your system when it does costing lots to fix.


Cheers,
Steve.

 

[atttech-2]

2 thoughts, without getting into suction side vs return side, instead of a check valve how about a normally open power actuated jandy, solenoid or ball valve on the drain line. The valve can be connected to your control panel on the same relay as the pump. When the pump is running the valve closes the wast line so it does not become a fountain. When the pump turns off the valve de energizes and opens up back to passive drain mode.

Second though going in a totally different direction if you have an auto fill how about converting it to a passive drain for the winter. If the auto fill is above grade like your skimmer take the float valve out of it and insert a snorkel (what I am calling it for some unknown reason) up to the level you want to maintain. At the house you insert a T in the line with a ball valve on the waist line. In the rainy season you turn the water off inset the snorkel and open the ball valve no laser level needed in fact the lower the line below the pool the better, as soon as the water level hits the top snorkel the draining stops. Only thing I don't know is will the line be large enough to drain fast enough for what you need and of course you have to have an auto fill to begin with. Bad diagram attached