# Thread: Drainage Plan Between Existing Concrete and New Pool

1. ## Drainage Plan Between Existing Concrete and New Pool

I'm looking for input on my planned drainage (green piping) that will run between my existing concrete slab (Spray-Deck applied later) and the coping. Basically, I want to make sure I have enough distance between the two to allow for adequate sloping of the new decking towards the existing slab. The existing slab has a slope to the left and toward the new pool, so water should naturally run toward the pool (drains 1-3), then left, then away from the house again (drains 5-7).

My plan right now includes seven 4" deck drains (Pour-A-Lid type), but given the slopes of the existing slab and the new decking, I'm thinking I may not even need the first 4 of them on the right hand side. Perhaps just the 3 closest to the 9" deep bench would be enough since all the water should end up there anyway. Does anyone see any issues doing that and basically eliminating the drain pipe between the drains 1 and 5?

Any issues with having only 12" - 23" of decking between the existing slab and the coping? I REALLY don't want to have to move the whole pool to the right and back if I don't have to.

2. ## Re: Drainage Plan Between Existing Concrete and New Pool

How much fall is there on the existing patio from deck drain 1 to deck drain 5?

3. ## Re: Drainage Plan Between Existing Concrete and New Pool

2-5/8" drop between drain 1 and 5. The straight line (as the crow flies) distance between those two points is 20.5'

4. ## Re: Drainage Plan Between Existing Concrete and New Pool

Drainage can be a very tricky issue. There may be engineers who could do calculations to figure this out or people with experience and a good eye. What is your plan in the area of drain 5? You will have over 3" of slope in about 3' from the pool to the existing deck.

5. ## Re: Drainage Plan Between Existing Concrete and New Pool

Yeah, I see your point. 3" drop over 12" length is steep. Maybe doable, but not sure. Definitely don't want a "step" right there, and I can't really move the whole pool to the right (due to property boundary. I also don't want to bring that side of the pool inward. The only other option may be to bust up some existing concrete to make the slope more gradual. But then the question becomes, how far back do I bust up and how does that new higher elevation affect the remaining concrete drainage (fighting a new up hill flow)? This is not good!

6. ## Re: Drainage Plan Between Existing Concrete and New Pool

Honestly for a project as nice as this replacing the existing slab would be a drop in the bucket compared to the overall project. It would also look much nicer. I wouldn't want a drainage swale that close to the pool. My advice would be to look at it with the builders you get bids from and keep your options open. Perhaps budget for demo and replacement just in case. Sometimes with drainage you have to look at the jobsite to really get a handle on it.

Good luck!!!

7. ## Re: Drainage Plan Between Existing Concrete and New Pool

I'm not sure about a drop, maybe a cup . Anyway, I definitely agree with getting with the builder, which I will do once I pick one. I shot some more elevations this evening with a better laser. It turns out there's more of a slope than I thought...almost 4.5" from drain 1 to drain 5. The picture below shows the elevations at various points with respect to the highest point (nearest the house). I've also shown the expected slopes (with angles) at these locations assuming 1/4" rise per foot from the existing deck to the back edge of the coping. The steepest slope is near drain 4 with a 18 degree slope (4" rise over 12" length). Not ideal, but not sure if it's worth busting up over 600 sq. ft. of perfectly good concrete. We'll see. Thanks for the feedback!

I do think I will eliminate drains 1-4 and move drain 5 further back and to the left. Mainly because drains 5-7 are the only ones I would be able to install on "flat" grade.

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