Considering revamp of overflow... What do I need to know?

[anonapersona]

My pool, about 10 years old, has a "fake" overflow. There is a grate in the pool itself, and a short PVC pipe, then it attaches to a flexible pipe that goes UP into the landscaping behind the pool.

Needless to say, it is pretty useless, since UP does me no good at all. As it is now, the excess water just makes its way around the back side of the pool shell I suppose. I do wonder if the flow of water may have undermined the pool itself. When the pool gets a lot of rain, it slowly gets out this fake overflow, not fast enough to prevent the pool from running over the edge in a heavy rain but it will drain an inch a day or something like that, until the water level is below the fake overflow.

In addition to this bogus overflow, this pool had a leak for the first 8 years, from the time it was built to the time we bought the property, so I think the concerns about damage from water flow are possibly serious.

So, we are thinking about how to run that line to a place that will do some good when we get 4" and 8" rains like we do here in Houston from time to time.

Now, as opposed to when the pool was built, you are allowed to drain into the sewer. But I fear that getting from the back yard to the front where the sewer clean out is will be tricky. Lots of tree roots and an old established sprinkler system to cross, as well as the pool lines themselves.

The other option is just to run the line partway, so that it drains onto the grass at some lower level in the side yard, not all the way to the front where the sewer is.

Does anyone have any advice or comments to offer? Should I pursue this, or reconsider?

 

[polyvue]

My pool, about 10 years old, has a "fake" overflow. There is a grate in the pool itself, and a short PVC pipe, then it attaches to a flexible pipe that goes UP into the landscaping behind the pool [...] When the pool gets a lot of rain, it slowly gets out this fake overflow.

Maybe a picture will help to visualize your predicament. What you describe hardly seems possible: no overflow pipe with an outlet that is above the water level of your pool is going to remove any amount of water without suction (aided usually by a pump.)

When I had my pool constructed we put in landscape drainage to the street; the overflow pipe (several inches above mid-tile water level) is connected via PVC to this drainage --- it's on a horizontal plane before dropping a couple of inches into the drainage pipe.

 

[geekgranny]

It is hard without pictures but how about running "that line" to a rock pit somewhere off from the pool. You would need a certain amount of drop in the line for gravity to get the water there. You can look up, on line, how much drop, say, how many inches per length, like for a gutter or run off drain; shouldn't be much drop. The pit could be covered with sod.

My parents had a drain the their basement that ran way out the back yard to some kind of pit covered with grass. I never knew where it was exactly as the grass over the pit didn't grow any differently than every where else. Their pit could handle the water from my mother's one station beauty shop, in the basement, the clothes washer and dog washing (200 lb dogs). So, in their case, it was probably a 3" pipe, or more, probably clay, (built in 1949) taking gallons at a time. Yours could be scaled way down, of course.

gg=alice

 

[geekgranny]

I just occurred to me. A friend of mine, disabled, has a pool that I check out a bit, when I'm over there. She's always having me hose out the juniper needles, from a couple of 3/4 inch or so PVC lined holes in the decking a few inches back from edge of pool. She says it is an over flow line. My pool doesn't have that, I'm not a pro, so I've questioned her every time, at first, now just grumble quietly and do it.

What happens is the water/debris goes out the hole into pool by same size hole above the normal water line. Her lot is small so the whole back yard is pool, concrete decking, and wood decking around three sides of pool from pool decking to fence. On the back side of yard, where the "holes" in decking are, the ground drops off about 4-5 ft to where the property line ends. Heavy, very "wild" woods start at that point behind her property. (She has BobCats come over her fence to drink from pool.)

I'll betcha those overflow drain lines run out the back side of concrete decking and are under the wood decking. Can't see it outside fence as fencing goes all the way to ground sort of like the skirting on a raised pier and beam house. I'll betcha what she has me hose out is a crude air valve of sorts to allow air into the lines going from pool to lower level drain hole. Evidently the overflow is working as she never reports her pool overflowing, and she gets almost as much rain, when it does rain, as we do.

I haven't ever put it all together in my mind until until thinking about this thread. Next time I'm over there I'm going to have to do some apologizing. She'll love that and I'll hear about it until one of us passes on.

gg=alice

 

[anonapersona]

Maybe a picture will help to visualize your predicament. What you describe hardly seems possible: no overflow pipe with an outlet that is above the water level of your pool is going to remove any amount of water without suction (aided usually by a pump.)

When I had my pool constructed we put in landscape drainage to the street; the overflow pipe (several inches above mid-tile water level) is connected via PVC to this drainage --- it's on a horizontal plane before dropping a couple of inches into the drainage pipe.

I cannot understand WHAT they were thinking... pool builder did put in the grate and the PVC but it just runs out 18". Perhaps the landscaper damaged that line when they built up the landscaping along the backside and added the corrugated tubing that runs nowhere. Maybe it went somewhere once but someone tore it up.

Such a line to the street, or to the sewer would have been so much easier to do when the pool was installed. Placing it in the same trenches, with the ability to control the slope. To do this after everything has been done and it all has grown in after 10 years seems impossible.

Is there some easy way to manage the need for slope? Especially as we cross pool and sprinker lines!

 

[polyvue]

I cannot understand WHAT they were thinking... pool builder did put in the grate and the PVC but it just runs out 18". Perhaps the landscaper damaged that line when they built up the landscaping along the backside and added the corrugated tubing that runs nowhere. Maybe it went somewhere once but someone tore it up.

Yes, I was reading over Alice's last comment and started thinking about the possibility that the builder had intended to put in an overflow line but didn't -- and that the line going up was as Alice described, some sort of air relief to an incomplete drain. My builder's subs also failed to complete the line initially -- it was dead-ended into dirt, and was completed properly only after I noticed it and had them revisit.

Without knowing exactly the grading on your property I would hesitate to recommend any particular solution, but you earlier suggested that you might be able to extend the overflow line from the pool out into a grassy area. As long as that area is below elevation of both the pool deck and the water line, that should work... even if it's just a pipe jutting out of the ground, angled down and away from the pool.

 

[anonapersona]

I think we can do that. We will have to dig under a huge Giant Bird of Paradise and sago palm, then remove a lot of large river cobble (bowling ball size, again, what were they thinking?) then trench alongside the pool cutting into a palm tree root zone. That will get us to the grass, but hard to say if that is above or below pool level at that point.

Then, we'd be looking at a lot of water on the grass, when it was wet already from a lot of rain. And that is right where I have to walk to get to the equipment pad. [sigh] Not sure if the chlorine would kill the grass, and I don't know what the salt content of our water is, after all this bleach.

I guess the first thing is to determine relative heights, just to see how far we'd have to go to actually get drainage. I'm thinking that once I'd read about using a hose to find what the height change is between one point and another, without having to worry about what was in between. I think I need to get a hose full of water, no air bubbles, then lower one end to a measured height above the drain level. Then lower the other end until it is just full of water. Since water finds its own level, then the height difference between one end and the other is calculated.

Then, at least I'd know if I can stop at the edge of the grass or if I have to go further to get effective drainage. Going past the equipment pad takes us over half way to the sewer.

Maybe all this needs to wait until I have to pool replastered or whatever.

 

[polyvue]

That will get us to the grass, but hard to say if that is above or below pool level at that point.

Then, we'd be looking at a lot of water on the grass, when it was wet already from a lot of rain. And that is right where I have to walk to get to the equipment pad. [sigh] Not sure if the chlorine would kill the grass, and I don't know what the salt content of our water is, after all this bleach.

The pros use a laser to determine relative elevation, but a sunken length of re-bar with a string attached works almost as well. How often does the pool overflow? If it's only a couple of times a year, perhaps you leave well enough alone and let it drain onto the deck (if it has proper drainage, that is.) If you have a non-SWG pool, the salt added by liquid chlorine is not going to be higher than 300-500 ppm, so the grass will live. Rain water (in Sacramento, at least) has only a neglible amount of sodium chloride.

 

[anonapersona]

I guess what I really need advice on is whether having several inches of water occasionally seeping out along the backside of the pool is a hazard.

The overflowing at the rim only happens maybe 2 or 3 times a year and will flow in a controlled direction around the house to a swale to the street. The overflowing though the grate to the pipe that seeps behind the pool happens a lot, anytime we get more than 1/2 inch of rain I'd guess. Maybe 3 times a month, more in winter, less in summer. When we get a good rain, all that water in excess of the first 1/2 inch will seep out around the back side of the pool into the ground, eventually under or around the house to the street. That water never returns the the swale for above ground drainage, it seeps through the dirt.

When the pool was leaking (I estimated 900 gallons a week, between rock coping and plaster several 1/8" to 1/4" gaps totalling maybe 1.5 square inches open to flow) we had seepage all the way around the property to the front curb where a brown slime and fuzzy algae would grow. Part of that was leaks in the irrigation system but as we located those and repaired, the leak in the pool still fuelled that slime, and the watertable was high enough to flood the water meter box near the curb.

I worry about what sort of damage that seepage for 10 years did to the foundation of the house and the pool, and now that the pool main leak is fixed, I am wondering if I need to address the seepage of this overflow grate. I'm really not sure it is important, since when the pool gets over the rim, it will flow down a reasonable path not towards the back door. I know that we get about 55 inches of rain a year here, I'll guess that maybe 12 inches or more would get out via this grate from Big Rains. Maybe since the ground is already saturated from rain, the seepage is not an issue at all??? (That is, am I worried about something that is not really important?)

 

[polyvue]

I worry about what sort of damage that seepage for 10 years did to the foundation of the house and the pool, and now that the pool main leak is fixed, I am wondering if I need to address the seepage

This is beyond my level of expertise. Hopefully, members in construction or excavation are able to answer this.