Input on winterizing a newly constructed perimeter overflow pool

[DougS78]

After a very long wait, our pool finally was finished in August and we've had a few weeks to enjoy it. Unfortunately, now our attention turns to winterizing it. Unfortunately we have a complex pool in a northern climate and so would appreciate input on what approaches we might take to winterizing the pool.

Pool is inground plaster finish. It has an overflow edge around the full perimeter (zero edge). Water overflows into a slot and then into a trough around the edge. Other than the 1" slot, the trough is covered by mortared deck pavers so they can't move or give access to the trough. The trough flows down into a perimeter line that drains into a reservoir buried a few feet away. All flow from trough to reservoir is gravity.

At issue is that the slot drain cannot be easily sealed due to its length and size. The trough drains cannot be plugged due to lack of access. Water cannot be allowed to pool in the trough or lines leading from trough to reservoir as they would freeze and crack. We also need to keep enough weight in the reservoir to keep it from rising up during the winter, but not so much water than it would itself freeze and potentially crack.

Pool builder gave some broad input on winterizing, but does not provide this service. Their solution was to keep space in reservoir for all water/rain/snow melt to flow directly from trough into the reservoir. Then add a significant amount of antifreeze to the reservoir and then monitor it to keep it from overfilling. Local pool service company is currently considering how best to winterize (and will provide the service) but doesn't feel that plan is ideal as will be hard to ensure no water/snow remains in trough and drains and goes through freeze/thaw cycles.

Any input on potential solutions would be greatly appreciated!

 

[Texas Splash]

Some thoughts to get us started:
- Will you be covering your pool with a solid cover? If so, would the cover expand far enough to cover the overflow edges and troughs?
- How far below ground level is the reservoir?
- Can you post some pics of everything?

 

[DougS78]

Thank you!

No cover on the pool as it wouldn't work with the slot drain and wet coping. Nothing planned to block the overflow slot at this stage, but Open to suggestions.

Reservoir is buried with hatch on top, about 2 feet of risers down to tank. Bottom of tank would be about 5-6 feet below grade.

Happy to post some photos. What would be most helpful? Pool as finished or some at plumbing stage?

 

[Texas Splash]

What would be most helpful? Pool as finished or some at plumbing stage?

Any/all you can provide. In your situation the more the merrier. It will help as we get more eyes on this discussion since your scenario seems to be a bit unique.

 

[DougS78]

Sure thing. I'll share several and try to explain what you're seeing.

At plumbing phase, showing the perimeter trough plumbing. Showing again after gunnite with pipes sticking up in each place that will become drains in the trough. All run together on the shallow end of the pool on the east side (toward pond). All of these were eventually cut down to bottom of the trough. The trough is roughly 4 inches deep and wide. coping is the fixed overhanging the trough so that only the first inch is open to allow water to flow in over the weir.

Once water is in trough, a main pipe then feeds out from that line on a downward slope to the reservoir. You can see the full site in the zoomed out picture in which they are digging/filling the reservoir. Its about 20-25 feet from the pool.

The reservoir/tank itself is fed on the high side as water drains from the trough. This is the top side of then tank. The water then leaves the low side of the tank via a 4 inch pipe and is pulled up back to the pump (4hp) on equipment pad. It then is cycled back (bypassing filter) to the pool in a 4" pipe. It then empties into the pool in the deep end in the front 2 of what look like main drains. The back 2 (and the one on the side of the pool) are main drains. The front 2 are where water is pushed out to overflow the pool water into the trough.

 

[Texas Splash]

Thanks for the additional info and pics. If you don't get some replies soon, post back or let me know and I'll try to tag a person or two who may have some experience with your situation.

 

[HermanTX]

The trough is roughly 4 inches deep and wide. coping is the fixed overhanging the trough so that only the first inch is open to allow water to flow in over the weir.

After this was finished, did the PB verify that everything gravity drains to the reservoir? That there is no low spot or dip that holds water? If so, then the main concern would be the reservoir filling up and holding back drainage from the trough. The assumption is that the trough and connected drainpipes are "empty" unless water is flowing through them. There is minimal risk of them freezing unless the reservoir is holding back the water.

Reservoir is buried with hatch on top, about 2 feet of risers down to tank. Bottom of tank would be about 5-6 feet below grade.

So with the hatch, the depth of the water in the reservoir can be measured with a rod marked off. How accessible is this with snow on top of it? Can you put a barrel or something similar over it to make it easy to access? Is it something you can monitor every couple of weeks? Mixing the reservoir with antifreeze is a good idea but only viable if it can be monitored. When the reservoir was installed, does it contain any type of float in it that controls the level of water in it? Such as to tell the pump to turn on or off dependent on level.

I have a friend that has reservoirs positioned on corners of his home to capture rainwater from his roof. They are buried underground, and he has sump pumps in the reservoir to pump the rainwater out. However, this is not in a cold climate so freezing is not an issue.

Maybe this will generate some thoughts for others to provide new ideas.

 

[DougS78]

Thanks for your input and excellent questions.

I have nothing from the PB on this. How would the PB verify if there were no low spots? I mean I can visually see into the trough and don't see any standing water once it runs, but I don't know how it could be determined if the pipe itself had a low spot or dip. I will say the PB has been a challenge to pin down on MANY things. Strong guess is that they did nothing to verify this other than that they saw water flow out into the tank.

The hatch should be accessible all winter. Even if a huge snow we could get at it in one way or another. Either a barrel over it or simply digging out. We rarely get more than a foot of snow that sticks around too long. The idea of a sump that pushes out water once it hits a certain point is a good idea. No float is installed now. This would be a great addition, though. Some ideas are to have some sort of a gizmo to vibrate and keep water from freezing and pair this with a pump set to keep it at a desired level. The only other wrinkle would possibly be evaporation as we also don't want the tank to go dry or it will heave up and break the plumbing. Keeping it at about half capacity seems like it should do this easily and provide plenty of room for water to flow.

I really like the idea of an autofiller/pump in there. It would be ideal to keep it at a good level all year round and to signal the pump to shut off if its about to run dry. To be honest, the size of the reservoir is a huge concern for me as it seems way to small for the purpose. Thats a different story, but would again be useful as the capacity is limited so narrow room for error.

 

[ajw22]

In Indiana the frost line is about 20" deep.

Is the pipe to the reservoir 20" or more deep?

As long as the water level in the tank is more then 20" below the surface I don't think you need to worry about water freezing in it.

I think your problem will be ice forming in the inlet to the pipe from the trough to the tank. If the pipe gets ice blocking the inlet then water and ice can accumulate in the trough.

How are the sides and bottom of the trough finished?

I think the trough and the trough drains will be your problem area. Without access to it all you can do is hope for the best. Global warming may bail you out until you have a winter with a real hard freeze.

 

[DougS78]

I appreciate that input. It really is hard to say what the depth is with much precision. I'd guess it's in the 20" vicinity. I could get a decent measurement of the outlet of pipe into the tank, but would be a challenge.

Your point about the place where the trough drains collect and go into the outlet to tank is well taken. At that point the 2 inch will feed into a 4 inch. Hopefully even if it freezes it will be minimal.

 

[DougS78]

In Indiana the frost line is about 20" deep.

Is the pipe to the reservoir 20" or more deep?

As long as the water level in the tank is more then 20" below the surface I don't think you need to worry about water freezing in it.

I think your problem will be ice forming in the inlet to the pipe from the trough to the tank. If the pipe gets ice blocking the inlet then water and ice can accumulate in the trough.

How are the sides and bottom of the trough finished?

I think the trough and the trough drains will be your problem area. Without access to it all you can do is hope for the best. Global warming may bail you out until you have a winter with a real hard freeze.

The trough itself is gunite, but coated with some additional cement to shape it. Drains are the 2 inch pipe.

 

[ajw22]

The trough itself is gunite, but coated with some additional cement to shape it. Drains are the 2 inch pipe.

Gunite is not waterproof. Something should coat the trough to make it waterproof.

 

[DougS78]

Hmm. Well, they did use some sort of paint on it. I don't know that I'd call it a waterproofing (it's not a thick substance) but perhaps that's it. What is typical for a waterproofing application?

This has a consequence for winterizing I presume?

 

[ajw22]

This has a consequence for winterizing I presume?

Depends how much the material needs to be protected from freeze damage.

Can the material withstand ice forming on it without damage?

Or does the material need to be kept ice free?

 

[HermanTX]

Well, they did use some sort of paint on it. I don't know that I'd call it a waterproofing (it's not a thick substance) but perhaps that's it. What is typical for a waterproofing application?

While the pool was full, the trough was constantly being flooded, so if the trough was "leaking", it would have showed some sign of wetness around the perimeter of the pool. Not sure this could be monitored based on your design.

One idea, and it may sound crazy, is to take pool noodle material and stick it in the slot around the pool. It could be cut that it would be 6-12 inches above the pool. Not sure this would prevent snow or ice forming in the trough. Others use this concept to prevent skimmers from cracking so, just trying to apply similar logic to your situation.

 

[Tcadwall0]

Might be a silly suggestion, but any thoughts on an aquarium heater in the tank? a submersible 300w might be enough to keep things from freezing in the tank. Especially if it is below frost line.

 

[DougS78]

While the pool was full, the trough was constantly being flooded, so if the trough was "leaking", it would have showed some sign of wetness around the perimeter of the pool. Not sure this could be monitored based on your design.

One idea, and it may sound crazy, is to take pool noodle material and stick it in the slot around the pool. It could be cut that it would be 6-12 inches above the pool. Not sure this would prevent snow or ice forming in the trough. Others use this concept to prevent skimmers from cracking so, just trying to apply similar logic to your situation.

So this would be an effort to keep water from getting into the trough in the first place....or at least greatly minimizing?

This was something we thought about, but I wasn't sure how well it would prevent water. But if the idea was to minimize volume that would presumably work. The slot is just an inch wide and inner coping slopes away from it. So no water would run into the slot, just what fell directly in. Some would still get in, but I can't think it would be much.

This would then minimize the chance of enough being in to freeze hard and case damage?

I am struggling to understand the part about sticking 6-12 inches above the pool. Can you clarify?

 

[DougS78]

Might be a silly suggestion, but any thoughts on an aquarium heater in the tank? a submersible 300w might be enough to keep things from freezing in the tank. Especially if it is below frost line.

Not silly at all. Thought of both a heater or a "gizmo" that creates enough disturbance on the top of the water to keep from freezing.

Thought is to pair this with a sump to keep water in tank at about half capacity (~300 gallons) which would serve to keep it from floating and allow capacity for a hard rain or snow melt.

There will soon be an outlet right next to the tank hatch so this should be doable (although still need to figure getting the wires routed into the tank.

The part I'm stuck on is how to attach the sump and heater? Sump would need to be raised to the right depth. Heater would need to be below that. Any ideas?

 

[HermanTX]

So this would be an effort to keep water from getting into the trough in the first place....or at least greatly minimizing?

This was something we thought about, but I wasn't sure how well it would prevent water. But if the idea was to minimize volume that would presumably work. The slot is just an inch wide and inner coping slopes away from it. So no water would run into the slot, just what fell directly in. Some would still get in, but I can't think it would be much.

This would then minimize the chance of enough being in to freeze hard and case damage?

I am struggling to understand the part about sticking 6-12 inches above the pool. Can you clarify?

My thought was that snow would pack in that 1 inch opening and possibly freeze in that trough. My thought was to fill it with something that would not allow the ice to form and expand. The purpose of the 6 inch height was to be above the depth of snow - so you knew where the edge was.