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NCalMatt 02-01-2010 03:55 PM

bringing down the water table?
My home was built about 35 years ago on a slab. Some of the HVAC ductwork is in the slab. One of the returns (pulls in air) is taking in ground water. There is drainage from the roof (~2,500 sq. ft.) into plastic piping that doesn't seem to have an outlet to the lowest part of my property. This weekend I'll be digging up the old and looking for blockages and sections that slope the wrong direction (I think there is some of that).
Does it ever make sense to put a sump pump system on the outside of a house to bring the water table down?

Scuba_Dave 02-01-2010 04:01 PM

If the water level has risen you could be pumping thousands of gallons of water
Your best bet 1st is to make sure all water from your roof is draining away from your property

1" of rainfall on your roof (2500 sq ft) will be ~1560 gallons of water
Multiply that out by surrounding ground to figure out how much water falls from rain near your house

NCalMatt 02-01-2010 05:03 PM

Thanks Scuba_Dave,

Getting the water from the roof away is my #1 priority. I guess I'm trying to figure out if it is overkill to put in a pump. Once I realized what was going on I dug a hole for a 5 gallon bucket with holes drilled into it and started a syphon. The bucket would drain and stay dry for a day or so, fill back up and then it has been dry ever since.

I'm 99% sure there are issues with the drainage coming off the roof. Once those are addressed, is it worth digging pits and putting in a pump?

Scuba_Dave 02-01-2010 05:26 PM

I have sump pump connected to a drain system - 5 pipes in all
It pumps 40gpm & can run for several minutes

You need a drainage system big enough to pump out enough water to keep the pump running for a while
A 5g bucket will not do much & your pump will burn out from going on/off

I've regraded around my house & added buried drains that take water 20-40' away from my house

ferris13 02-01-2010 06:06 PM

I had this same issue. My family room is on a slab. One day I heard some water tricking in the basement from HVAC leading to the slab. Drilled a hole into it to let it drain. I had to MacGyver a rubber maid tub an hose until I was able to work outside.

My home is 25 years old. The builder had also dumped the downspouts into pipe that went out into the yard (bed of gravel). I tested the drainage by dropping my hose into it and within a few minutes it was overflowing. Over the years the pipe just clogged 95% full of silt. I dug them all up and replaced. I also decide to install a french drain from one side of the yard to the other and diverted the water around the house. I dug 180ft, under my deck, added stone, socked pipe, more stone....oh yeah, it sucked. The HVAC where the issue was reined dry the rest of the year (and e had some big storms) The true test for me will be this spring when all the snow begins to melt. Good Luck.

bmelanco 02-06-2010 04:19 PM

Yes, step one is to make sure you get all your roof drainage clear of your foundation (outlet down slope) and that you hav sloped the land near your foundaton so water runs away from it. If it is just a run off problem this will fix your issue in less than a month or so. If you notice the problem reoccurs shorlty after periods of heavy rain and/or snow melt then you likely have a ground water problem. In either case I think your best bet would be to rerun te HVAC line. If you wanted to finish your basement (which I would only do if it is a runoff problem) then you could consider a sump pump.

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