Flooded

This is a story of me afro-engineering a solution to some flooding that happened to my rear lanai. Now that there is a pool behind the house, what was our back porch has been closed off by an electric hurricane screen. There is some outdoor furniture and a TV in there, and it now serves as a sort of “Florida Room” and a place to store outdoor items when a hurricane comes. More on that in a different post.

We had a thunderstorm come through on Saturday, and it was a fairly strong one. We got just over 3 inches of rain in less than 45 minutes. That caused a bit of an issue. When we put the pool in, the contractor put a drain in place that lies at the end of the pool deck closest to the house. It looks like this.

That is just a slot in the concrete about 2 inches wide and 4 inches deep. It discharges on both sides of the slab. Right above where that discharges, the downspouts from the gutter discharge. I dug a trench at that point, and ran a 4 inch corrugated pipe that runs about 20 feet back from the house. At the end closest to the house, it looks like this (pictured is not mine, it’s from the Internet):

The discharge was one of these valves.

When the pipe fills with water, the weight of the water causes the valve to open. Well, as near as I can tell, the rain was coming down so hard that the drains were quickly overwhelmed, the area near the inlet to the drain pipes was soon underwater, and this caused a backup that flooded my rear lanai with about an inch of water. The rug out there was saturated, but luckily it’s an outdoor rug, so a couple of hours and a fan soon dried it out, no harm.

While it was raining, I went outside to see what the problem was. It had been so long since we had gotten any real rain, everything was clogged with dead oak leaves: the downspouts, the intake drains, all of it. So I cleared the leaves out, but that didn’t help a lot, and got me bitten on the hand by a rather large, angry spider that had been nesting in the leaves.

I spent Sunday digging up the ends of the drain pipe, and I replaced the intakes with this:

Since it is taller and not flat like the old ones, the hope is that this grate can handle more water AND is not likely to be clogged with leaves. Then I also replaced the discharge valves with these.

I am hoping that this will be large enough to allow more flow through the pipe. According to my math, a 4 inch corrugated pipe that is 20 feet long with a 1 inch drop every ten feet should be able to move about 75 gallons per minute. I have two of them (one on each side of the house) so I should be able to drain about 150 gpm.

Also according to my calculations, a rate of 3 inches of rain in 45 minutes is about 30 gallons per minute. This system should be able to keep up now, if I can keep it free of leaves. I guess we will find out next time we get a good rain, which in Florida is about once a week or so.

Keeping water out of the house is important, and no all prepping is sexy. Hope this helps someone else.