French Drain for New Build

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Duke77

Duke77

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Aug 22, 2018
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Hi All,

I have been told by neighbors and other folks in my area that I should seriously consider installing a french drain and sump around my pool. Since I am early in the process, I only have a 22x48 hole at ~36" deep, I would appreciate any advice you may have on how to go about it. I get the general concept of the french drain but I am unsure how to apply it in the context of an inground pool. The soil around here seems to have a good bit of clay in it and doesn't seem to absorb water really well. (See the not to scale diagram below)

Where should the french drain be located? Sump pit?

The pool will eventually have an 8' deep hopper, do I need to install a french drain there as well?

Thank you.
Drain (3).png
beforeExcavationLookingNorthWest_lowres.jpgafterExcavationLookingSouthEast_lowres.jpg
 
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The slope of the terrain dictates where to place the french drain to keep water run off from entering the pool (it's also used to keep ground water at bay). Does your house have gutters and downspouts? Where is the lowest point of the land compared to the pool?
 
I notice that you have standing water in your yard. That is likely why these suggestions from neighbors have arisen. I would agree that a french drain around the outer 3 sides of the pool, leading to a sump with a pump in it which pump the ground water away from the pool via a pipe out of the area, possibly to the street or the wood if that won't drain back towards the pool. You may not also be able to drain to the road due to local oridinances. This is all especially important with a vinyl pool as they can be susceptible to the liner floating with substantial water pressure from the outside even if the pool is full. I'm assuming you will have concrete on the house side of the pool.
 
RMcGirr83 said:
The slope of the terrain dictates where to place the french drain to keep water run off from entering the pool (it's also used to keep ground water at bay). Does your house have gutters and downspouts? Where is the lowest point of the land compared to the pool?
Click to expand...
The house does have gutters and the downspouts are located right above the catch basins. (See diagram above) As for the lowest point, it would be located near the tree line. The way the slope is right now is not too bad but the ground doesn't absorb water really well, it tends to sit on the surface for days after a rain shower.

Would it make sense to set up a french drain in the over dig of the pool and locate a sump pit and pump near the equipment pad?

Thank you!
 
bmoreswim said:
I notice that you have standing water in your yard. That is likely why these suggestions from neighbors have arisen. I would agree that a french drain around the outer 3 sides of the pool, leading to a sump with a pump in it which pump the ground water away from the pool via a pipe out of the area, possibly to the street or the wood if that won't drain back towards the pool. You may not also be able to drain to the road due to local oridinances. This is all especially important with a vinyl pool as they can be susceptible to the liner floating with substantial water pressure from the outside even if the pool is full. I'm assuming you will have concrete on the house side of the pool.
Click to expand...

Thank you for the advice. You are right, I plan on having concrete between the house and the pool and proper surface drainage.

I have a few more questions:

How deep should the french drain be located?

What about the deep end? If I capture the water and the depth of the concrete collar, do I need to worry about water below that depth?

Is the EZflow product worth it?
 
I think having it in the overdig area would be ideal, but let's bring @jimmythegreek in for his thoughts on specifics as he works a lot with vinyl, though in a different locale.
 
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The overdig works well. I usually hard pipe sdr35 green pipe thats perforated. When you do the collar you slope back concrete away from walls. Use high quality filter fabric 6 ft wide amd drape the sides of over dig onto the collar like a Z but backwards. Lay pipe around pool with tiny bit of pitch back to a sump pit. It can be anywhere. 10 or 12 inch pvc is good amd get an end cap. I dig the pit to level with pool bottom. Clean stone amd fabric al around it. Drop the drain pipe in at whatever height it comes in on. Backfill with 3/4 clean stone amd wrap over it to the pool wall at the height you need to begin your coping base or concrete deck. Liner will never float. If you can pitch the pipe to daylight with gravity that's the best way even if it has to go a ways out instead of a pit
 
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jimmythegreek said:
The overdig works well. I usually hard pipe sdr35 green pipe thats perforated. When you do the collar you slope back concrete away from walls. Use high quality filter fabric 6 ft wide amd drape the sides of over dig onto the collar like a Z but backwards. Lay pipe around pool with tiny bit of pitch back to a sump pit. It can be anywhere. 10 or 12 inch pvc is good amd get an end cap. I dig the pit to level with pool bottom. Clean stone amd fabric al around it. Drop the drain pipe in at whatever height it comes in on. Backfill with 3/4 clean stone amd wrap over it to the pool wall at the height you need to begin your coping base or concrete deck. Liner will never float. If you can pitch the pipe to daylight with gravity that's the best way even if it has to go a ways out instead of a pit
Click to expand...

Thank you so much, this is great.
 

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Duke77 said:
Thank you so much, this is great.
Click to expand...

As with most things, pre-planning is very important. I would suggest getting a laser level or just a simple builder's level and figuring out your elevations and drainage first.
Where does that existing go to?
As Jimmy mentioned, if you can daylight the drain line it is by far the best even at additional cost. If daylight is possible then you should start there and get the drain up to the pool excavation area. When digging drainage always dig from low to high. This will allow you to have a nice dry hole for the dig without having to worry about pumping.

In addition if you want to re-use that clay it is usually best to dig it and place and roll it in the same day or at least before a rain. If you figure your elevations you should be able to strip off the organics on the lower side of the pool fist and place the dirt there as you dig.

You should also never leave that clay like it is seen in the picture. All that loose clay in the bottom of the hole will just turn to muck. The bottom of the hole should always be cleanly scraped off with the bottom of the bucket and pitched to drain or pump location.
 
The drain line comes out below the lowest (corrected from high test) feeder. The access to daylight is based on site. Many will have only minimal drop available and thus need a pump to move it elsewhere via a higher pipe.
 
You understood it right. The pit is deep for as needed pumping for liner changes etc. The drain exits even or below the lowest inlet line to daylight. With gravity flow and a collar top drain the liner will never float. Rich D makes excellent points on digging.
If you cant get elevations for gravity then a pump is the only way. Dont feel bad i have 3 pits on the side of my pool was a royal pain
 
I heard clay and french drain! If your soil is like mine, DO NOT USE a french drain or a drain well until you do below. This is a cheap test you can do and it will save you a TON of frustration!!!

Before you install a french drain, please do a soil drainage test. Not sure if someone mentioned this but your soil needs to drain water effectively or a french drain is going to compound a problem.
Use a water test like this https://www.treepeople.org/sites/default/files/pdf/resources/How-to Test Soil Drainage.pdf to determine the soil drain rate. Dig the hole, fill it with some water, measure the drainage.
If you aren't draining 1"/hour then the french drain isn't going to be of much use.
If it's less that .5"/hour don't do the french drain. If the soil is clay it's not a great fit for french drain.

I live in georgia, clay soil. Did the test and I know if I had done a french drain it would have been a disaster.

PS - you can dig further than 1 ft. Dig as deep and you think the french drain should go. I dug mine about 2.5 ft deep. Also if you can dig through the clay level to a drainable layer underneath awesome. I could not :(
 
Agreed. I don’t see a french drain (input) with a pit/trench downstream to allow the water to leech down working in soil that retains water. I’m not sure the OP is discussing using a French drain that empties to a pit that leeches out, but rather a gravity based (or pumped) drainage system to a remote area. A french drain by definition is the pipes used to collect (or distribute like septic lines) the water. He’s looking at french drain on the input and another method for the output.
 
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Thank you all for the valuable feedback. I will be surveying to see if there is any way I can get a line to daylight. This clay is giving me nightmares. I have the shelf dug out and we got a thunderstorm this morning. Now I pumped all the water out but I am left with 4-6 inches of muck. It is going to take days if not weeks to dry. I am seriously starting to begin to think that this soil cannot support the 1500lbs per sq. ft. required by the manufacturer of the pool kit. I have yet to see the bottom fully dry, the best I have seen so far is a heavy dough-like consistency with a lot of "bounce" to it.
 
Duke I build on that all the time. I've had to make 40x60 tarp tents to be able to do floor and liner. Powder lime draws moisture out. If you cant keep it dry put a sump pit in the actual pool hopper. Skim the slime out and replace with 3/4 clean stone it will tighten right up. I have a 36" bucket for the excavator with no teeth just flat angle iron edge its my clay scraper
 
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