How to address extended patio rain water drainage issue?

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  #1  
Old 11-01-11, 11:12 PM
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How to address extended patio rain water drainage issue?

I'm in Phoenix, AZ and have drainage issues in my backyard during monsoon season.

I purchased this house a couple years ago. The previous homeowner put in the extended patio. It slopes away from the house but all the water flows to the back to the fence. It seems to me the patio should have been designed so water flows to the left so it can go around the house.

The previous homeowner attempted to resolve this issue by putting in a french drain (the red line in the pics). As you can see from the pics it did nothing.

I'm in the process of redoing a lot of the backyard and I would like to resolve this problem. I plan on putting grass in the backyard. In the 1st pic, to the left, you can see I've started to clear rock and this is where grass will go.

Does the extended patio need to be redone? Or are there other options?

Thanks!







 
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Old 11-02-11, 12:27 AM
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Stupendous,

Welcome to the forums.

If the previous owner installed a french drain where your red line shows it to be, he obviously didn't think it all the way through. What is the grade around your property? It would appear that this puddle (or small lake) is happening at the lowest point. Water does that! If it's uphill from this area to the street, you'll need to install a sump pump in order to move the water uphill.

Replace the paver patio? Probably not, but once you get the drainage issue resolved you'll be able to tell more about that.
 
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Old 11-02-11, 08:24 AM
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My property is graded and sits higher than the street. You can see the rest of the backyard sits higher. The low point in my backyard was created when the extended patio was put in. I could lower the area to the left, where I've cleared the rock and plan to put in grass, but that would create another issue because then that part of my yard would not sit high enough to direct water down my property to the street.

So if the rest of the property is fine I don't need a sump pump any more? Still seems the patio has the wrong slope. If the end of the patio sits lower how can a french drain be used to gravity feed towards the front of the property. If the patio had sloped down to the left a drain could have been put in place there to catch the water and carry it to the front of the property.

Thanks.
 
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Old 11-02-11, 09:18 AM
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OK, there's a french drain across the outer edge of the patio, but where does it go? The way you sketched it in, it appears to simply parallel the outer edge of the patio, with high spots in the yard at both ends of it. If that's the case, you need to continue it to the street, down one side of the house or the other, so the water has a place to go.

The problem isn't how the patio was sloped but rather that a low spot was created at the outer edge of the patio with the water given no way to get out of that area.

How far is it from that low spot to the street? What is the grade difference between those to points? (Is the street a foot lower; a foot higher; same elevation?)
 
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Old 11-02-11, 10:50 AM
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Typical 'french drains' are gravity flow, meaning they have a high end and a low end or ends. Whatever water gets captuered flows to the low end and then usually to daylight. Which is where the pipe sticks out of the ground, not up but horizontal. If your yard etc has no area where the pipe can stick out you need to dig a hole at the end of the pipe, put in a catch basin (I've used 5 gallon buckets up to 55 gal drums), and set a sump pump into it whenever the rains come. Hook the pump to a garden hose and run it to where the water can safely drain away from your house (frequently the street). When the pump isn't needed, take it out and cover the catch basin with a lid or something more decorative. Good luck.
 
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Old 11-02-11, 07:30 PM
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Originally Posted by lefty View Post
OK, there's a french drain across the outer edge of the patio, but where does it go? The way you sketched it in, it appears to simply parallel the outer edge of the patio, with high spots in the yard at both ends of it. If that's the case, you need to continue it to the street, down one side of the house or the other, so the water has a place to go.

The problem isn't how the patio was sloped but rather that a low spot was created at the outer edge of the patio with the water given no way to get out of that area.

How far is it from that low spot to the street? What is the grade difference between those to points? (Is the street a foot lower; a foot higher; same elevation?)
Yep, it only ran parallel. And with the way the caps were at the ends water would enter there and flow to the flooded area. I pulled the tubing out of the ground and there was also a lot of dirt in it, too. A very bad attempt at a french drain.

This weekend I'll see if I can figure out the grade difference between my street and the low point created at the end of the patio.
 
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Old 11-06-11, 10:38 AM
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The base of the patio is ~2.75" higher than the sidewalk at the front of my property. The distance is ~110' 3" assuming a straight line, which it's not because my house sits between the patio and front sidewalk.

Starting at ~86' 10" my property is ~5.5" higher than the sidewalk at the street. This height increases as you move further back in my backyard.

With such a low slope, I don't see how a french drain to the front of my property will work. It seems I will need a catch basin with sump pump in my backyard.
 
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Old 11-06-11, 02:14 PM
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Stupendous -

You obviously have a back yard that will not drain to the street without assistance. The pump is an obvious solution. This that the rare, but seasonal monsoons you get the rest of your yard will also be saturated.

One solution is to properly install a french drain (perforated pvc with holes at 4:00 and 8:00) that is level and leads to a sump pit or crock pot containing a sump pump. From the pipe, use a solid wall pvc buries toward the street or lower area in the front. A garden hose would be inadequate, a nuisance and ugly. For best appearance and practicality, you can install a "pop-up" bubbler that lets the water out (when the is some) and distributes it to the yard and for runoff and follow the natural drainage pattern the was there before the house was built.

Make sure the backfill under and around the drain is the best size locally available to increase the available collection area with a fabric separating the existing soil (a lot of fines) from the fill used.

Dick
 
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Old 11-06-11, 06:22 PM
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Dick beat me to the punch, but exactly what he said.

Reinstall what you HAD for the french drain, but do it properly. Solid perforated pipe has a line of 2 holes. Orient them down (4 o'clock and 8 o'clock) and put the pipe in a sock to keep the dirt out. Slope it down to a sump, probably at the left end, based on your photos. If you use corrogated ADS, it's have slots at 90 degree increments. Orient them upper-left and upper-right -- lower left and lower right (NOT top and bottom and each side).

Pay a lot of attention to his last paragraph about the backfill. Whatever is available locally, but at least 1" minus. (One inch is the size of the rocks. Minus means that it'll have 'fines' as well, down to about the size of sand included in it.)

A pump in the sump, with solid pipe for the discharge line going to the street, or stopping just short of that with a pop-up outlet. That line should be 1-1/2" or possibly 2" ABS. I would use a plastic or concrete for the sump -- something that won't collapse and won't rust.
 
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