Help with downspout drainage issues

[bud16415]

Dig that trench a whole bunch deeper and wider and go in both direction, perferated pipe and fill the trench with crushed gravel.

Just some rough calculations here if the area under roof and the slab was 20x30 or 600 sq. ft. and you got a rain fall of 1” per hour that would be approximately 400 gallons of water per hour. With a 50 gallon drum that would need dosed 8 times per hour or approximately every 8 minutes. or a 6 gallon per minute flow rate pump running continually during that rain. The idea behind a larger dosing tank and higher flow pumps is based around duty cycle. Some pumps are not rated to run nonstop for long periods of time. The estimate of one inch of rain per hour is also not any kind of record rain fall for Florida there are reports of 3 to 6 inches per hour during storms with flooding conditions.

These type calculations are why you see a 5 acre retention 10 foot deep pond next to a Walmart now. Where land is a premium the ponds are going in under the parking lot. We have a new dairy queen here and the whole parking lot is gravel except a tiny road for the drive thru. I asked them when they would pave the lot and they said never. The cost was unbelievable as they would have to buy several homes and tear them down to build a retention area for rain water.

If the OP was to try and leach the water away by digging wider and deeper trenches on that narrow strip of lawn he may well not have enough area. You also have to take into account that it is raining on that area at the same time. Just like a septic system I would have the soil tested for peculation times and then decide if that plan was feasible.

 

[Blivit]

Just some rough calculations here if the area under roof and the slab was 20x30 or 600 sq. ft. and you got a rain fall of 1” per hour that would be approximately 400 gallons of water per hour. With a 50 gallon drum that would need dosed 8 times per hour or approximately every 8 minutes. or a 6 gallon per minute flow rate pump running continually during that rain. The idea behind a larger dosing tank and higher flow pumps is based around duty cycle. Some pumps are not rated to run nonstop for long periods of time. The estimate of one inch of rain per hour is also not any kind of record rain fall for Florida there are reports of 3 to 6 inches per hour during storms with flooding conditions.

These type calculations are why you see a 5 acre retention 10 foot deep pond next to a Walmart now. Where land is a premium the ponds are going in under the parking lot. We have a new dairy queen here and the whole parking lot is gravel except a tiny road for the drive thru. I asked them when they would pave the lot and they said never. The cost was unbelievable as they would have to buy several homes and tear them down to build a retention area for rain water.

If the OP was to try and leach the water away by digging wider and deeper trenches on that narrow strip of lawn he may well not have enough area. You also have to take into account that it is raining on that area at the same time. Just like a septic system I would have the soil tested for peculation times and then decide if that plan was feasible.

I did some of these same calculations using NDS website. I calculated square footage of around 790 sq-ft. NDS lists the 25 year average rainfall for my area at 3" per hour. Using these numbers and their drainage calculator it says 24.6 GPM of liquid flow. What I am not sure of though is if I would split the sq-ft in half since there are 2 downspouts. That would obviously split everything in half but either way, it is a lot of water. Granted, unless it is a hurricane or tropical storm, the heavy rains here do not last for very long.

I too am not sure I will have enough area/proper soil to leach the water. It is mostly sand where I had stopped digging but I think it is more clay deeper. Putting in some sort of dry well with a pump may be my only choice here.

 

[bud16415]

Of course I didn’t have your dimensions I was just taking a guess based around the photos. If the other downspout is taking the water a different direction then you wouldn’t add it in to this problem location.

The way they do peculation test here is they dig a hole so large and so deep and then pour in X amount of water and time how long it takes to be absorbed. Then they wait so long and do it again. Based on the times they can recommend the type of system needed. For septic systems you can fail two ways one being too fast the other being too slow. In your case too fast isn’t a problem. But you are dealing with much greater amounts of water than a septic sees over a shorter time span. Many of the new mound systems they are building here for septic are 30x30 or 900 sq ft of leaching surface and only dosing the ground once every few days.

25 GPM is a good size pump if you decide to go that way. Not sure what size pipe that requires right off hand. You are right though it needs to be sized for the peak usage or you need lots of capacity for storage.
I put a French drain about 200ft long in my old house. My friend had a backhoe with an 18 inch shovel so that’s the width I made it and went about 4 foot deep and filled it to the top with baseball size pieces of a product they sell here made from recycled concrete. The drain allowed for holding and absorbing lots of water and the end was open to a ravine to take away flash flooding. It worked great.

 

[Blivit]

Of course I didn’t have your dimensions I was just taking a guess based around the photos. If the other downspout is taking the water a different direction then you wouldn’t add it in to this problem location.

The way they do peculation test here is they dig a hole so large and so deep and then pour in X amount of water and time how long it takes to be absorbed. Then they wait so long and do it again. Based on the times they can recommend the type of system needed. For septic systems you can fail two ways one being too fast the other being too slow. In your case too fast isn’t a problem. But you are dealing with much greater amounts of water than a septic sees over a shorter time span. Many of the new mound systems they are building here for septic are 30x30 or 900 sq ft of leaching surface and only dosing the ground once every few days.

25 GPM is a good size pump if you decide to go that way. Not sure what size pipe that requires right off hand. You are right though it needs to be sized for the peak usage or you need lots of capacity for storage.
I put a French drain about 200ft long in my old house. My friend had a backhoe with an 18 inch shovel so that’s the width I made it and went about 4 foot deep and filled it to the top with baseball size pieces of a product they sell here made from recycled concrete. The drain allowed for holding and absorbing lots of water and the end was open to a ravine to take away flash flooding. It worked great.

The other downspout is on the other side of the patio so I guess I can split the calculations.

Regardless of the results of the soil percolation, it would occur next to the house or next to the pool depending on which direction it went. Being close to either structure...is that even advised?

 

[nealtw]

So if you get the water to the road, where does it go?

 

[Blivit]

So if you get the water to the road, where does it go?

There are storm drains that it flows to. I've watched the flow at the curb and it is actually quite strong in one direction. I haven't looked yet to see where the closest drain is to my house but I have yet to see my street flood.

 

[bud16415]

So if you get the water to the road, where does it go?

Away.

When you have a state that the tallest mountain er hill is 350 ft above sea level and most of the state is maybe 20 ft above there is nowhere for water to go. I guess it’s better than being below sea level though.

 

[nealtw]

So you have to find out what that drain is sized for. I would be talking to the city for suggestions.

 

[nealtw]

Away.

When you have a state that the tallest mountain er hill is 350 ft above sea level and most of the state is maybe 20 ft above there is nowhere for water to go. I guess it’s better than being below sea level though.

So if the street drain gets to much water, there is some where it will go, just maybe not next door.

 

[bud16415]

In Erie after a big rain it’s not at all uncommon to be driving along the Bayfront and the man hole covers blow off and you get a 3’ column of water blowing up like old faithful in the middle of a busy road.

 

[Blivit]

IF I went the route of putting in a barrel/dry well/whatever you want to call it with a pump, would this effectively be what I would be doing?:

[ame]https://www.youtube.com/watch?v=6-KAOdOHwKA[/ame]

What is the container they are using here?

 

[slownsteady]

A couple of thoughts: First, how is the downspout situation on the other side? Where does that water go, and how well does it get there? You could create the mirror image on this side if it's good.
Second, the drywell has to either hold the water long enough for it to dissipate into the ground or long enough for the pump to send it someplace. You notice in the video above that the guys still had to lay a discharge line out to the street from the sump pump. That is something you were resisting. But if you have to lay the line anyway, maybe you don't need the pump, if gravity is on your side.
Third, about the obstacles on the way to the street: dig a couple of exploration holes to find the location and the depth of the water main and the sprinkler line. The sprinkler may be so close to the surface that you can go right under it, and the water main may be so deep that it is not a problem. Sandy soil is a pretty easy dig, or you can hire a machine (or a guy with a machine) to make that part easier.

BTW: use primer before you cement plastic pipe together.

 

[Blivit]

A couple of thoughts: First, how is the downspout situation on the other side? Where does that water go, and how well does it get there? You could create the mirror image on this side if it's good.
Second, the drywell has to either hold the water long enough for it to dissipate into the ground or long enough for the pump to send it someplace. You notice in the video above that the guys still had to lay a discharge line out to the street from the sump pump. That is something you were resisting. But if you have to lay the line anyway, maybe you don't need the pump, if gravity is on your side.
Third, about the obstacles on the way to the street: dig a couple of exploration holes to find the location and the depth of the water main and the sprinkler line. The sprinkler may be so close to the surface that you can go right under it, and the water main may be so deep that it is not a problem. Sandy soil is a pretty easy dig, or you can hire a machine (or a guy with a machine) to make that part easier.

BTW: use primer before you cement plastic pipe together.

The other side floods as well, just not as bad. It is also easier to deal with so I am starting with this, the difficult side, first.

You're right, I was hesitant to run a line out to the street bit that was when I thought it would be a 4"pipe in a deep trench. For some reason the idea of just the discharge line from a pump didn't cross my mind. A 2" pipe relatively close to the surface would be much easier to deal with. It is possible too that gravity could be on my side in this case. But, I am not sure if a 2" gravity discharge would be enough.

I am not sure how far down the irrigation lines or water main is, I will need to check those.

 

[oldognewtrick]

I don't know about your area, but around here we can call the utility company and they will come and mark where all underground services are located.

 

[Blivit]

I don't know about your area, but around here we can call the utility company and they will come and mark where all underground services are located.

Same here. I had that done last month so that is how I know where the water main is. I don't know how deep it is though. Nothing else was marked on that side but I know my irrigation lines start there.

 

[nealtw]

In the great scheme of things an irrigation line would not be a big fix.

 

[slownsteady]

4" pipe does not have to be very deep under a lawn. Just make sure your outlet end is lower than your inlet end. You don't have frost conditions to tend with.

 

[beachguy005]

Frankly, I think you're making the proverbial mountain out of a mole hill. It's Florida....we get a ton of rain and most often it happens very quickly over a short period of time. You have a gable roof which doesn't help. Hip roofs are better in Florida not only for wind resistance but for shedding rain water also.
You can lay a bunch of pipe and put in a couple of pumps, but your patio is graded away from the pool and toward the house and that's part of the issue. Rainy season will be over soon but in the meantime you should do as most Floridians do and that's to except that anytime you're getting rain amounts of 2 or 3 inches per hour, you're going to get some flooding.

 

[frodo]

Dig that trench a whole bunch deeper and wider and go in both direction, perferated pipe and fill the trench with crushed gravel.

with the limited yard area.

what happens to the water during a sur-nuff frog strangler rain?

the yard will flood,

In my opinion, the yard area is not big enough to use perf pipe and gravel

my opinion, and a dollar, might get you a cup of coffee :beer:

 

[Blivit]

Frankly, I think you're making the proverbial mountain out of a mole hill. It's Florida....we get a ton of rain and most often it happens very quickly over a short period of time. You have a gable roof which doesn't help. Hip roofs are better in Florida not only for wind resistance but for shedding rain water also.
You can lay a bunch of pipe and put in a couple of pumps, but your patio is graded away from the pool and toward the house and that's part of the issue. Rainy season will be over soon but in the meantime you should do as most Floridians do and that's to except that anytime you're getting rain amounts of 2 or 3 inches per hour, you're going to get some flooding.

I have been here long enough to know we get heavy, short rain for the most part and I have been dealing with this. In the grand scheme of things, no it's not that bad but it is more of an annoyance and something I would like to address before it gets worse and possibly reaches the house.


The patio is sloped in both directions toward the channel drain so it is more of a "V" with the drain in the center. Good in theory but once that water is coupled with the downspout on either end it is just too much to handle.