Do sumps pumps and drain tiles create a self fulfilling prophecy?
This may seem like an odd question so let me explain myself, and to be clear it is mostly philosophical and out of curiosity.
I own/have owned/lived in many different buildings in the Chicago area. My parents house is also nearby.
None have a sump pump/pit (and possibly no drain tiles), all have basements. I recently bought a house that was without electricity for quite a while. It has a sump and drain tiles. After losing electricity it would flood with any rain, this is even after extending all downspouts significantly away from the building. I would borrow electric from my neighbor and pump it out but I could watch the sump pit fill back up. I had the soil tested and it came back as great soil (clay all around) with no groundwater at 15′ So basically the foundation is in a clay bowl and the porous soil created by digging to create the foundation is where water infiltrates into the drain tile and into the sump pit and into the basement. Basically no electricity means eventual water in the basement.
On to my question, as I mentioned none of the other houses I have owned, rented, lived in etc in the area has/had a sump pump and pit (including one in the same neighborhood as the flooding house) and none of these houses have ever had water in the basement.
This begs the question does the sump/drain tile combo create a self fulfilling prophesy of flooding (if their is no electricity or if there is a pump failure) since you have created this path specifically for the water to infiltrate (in which case shouldn’t the sump pit be external to the building somehow? giving you a few more hours of dryness if you have no electric) or is it that the houses with no sump are just lucky?
Finally, I don’t know any builder or architect who build’s a basement without a sump anymore (due to the prevalence of overhead sewers now???) but how was it determined before that all these other buildings did not need a sump pump and pit (and remained dry) and all of the sudden every building needs one?
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Replies
Micheal,
It's one of many decisions you need to make when designing a house which goes to a fundamental difference in approach among builders - especially green ones - as to how active and reliant on technology a house should be. in some ways it can be characterized as a trade off between efficiency and resilience. Incorporating advanced electronic controls in appliances such as mini-splits or PV systems yields real dividends, but at some cost in both the chance of break downs and the owner's ability to effect repairs without help. Designing a drainage system necessitating mechanical pumps speaks to this too. There is no right answer. Only what you are comfortable with.
Michael,
In general, sandy soil is better drained than clay soil. Other factors being equal, a site with clay soil is more likely to be damp than a site with sandy soil.
Every site is different, so your attempt to compare the performance of houses at different sites is merely anecdotal. I'm afraid it doesn't prove anything.
It sounds like you are thinking that it's possible to build a concrete basement that is so watertight -- one built like a submarine, perhaps -- that no provision for drainage is needed. A few people have tried to do that, and they have failed.
If the hydrostatic pressure is high enough, water will enter a concrete basement, no matter how much you try to caulk the cracks. The advantage of having a sump equipped with a sump pump is that you have equipment to handle the water entering your basement.
If your area is plagued by regular power outages, you should invest in a sump pump with battery backup.
If the basement slab is close to the local water table, it'll have moisture issues during periods of high rainfall, independent of soil type- when the tide is high, it's high.
Sump pumps are one solution for managing that, slab on grade foundations (and no basement) are another.
So I spoke with a local gc about this and the answer is yes, in a way drain tiles with a sump (and overhead sewers) will almost always flood with no power. ( FYI to Martin I was not thinking you could build a completely waterproof basement just wanted to get to the bottom of the question.)
The reason the other houses have not flooded with no sumps is because they have below ground sewers and any water going into the house and drain tiles simply goes straight to the sewers, which is great if everything is functioning well. However, cities and towns don't like this anymore since it can tax the sewer system and has the risk of sewage backup into the homes. Many municipalities are separating their storm water and waste water sewers. (Ours requires storm water to go first into a cistern with a flow reducer that allows the water into the municipal sewers)
To avoid the backup problem overhead sewers are now typically being installed. The home I have that flooded has overhead sewers. But with overhead sewers any water that is in the basement needs to be pumped overhead or it will build up and flood (waste or storm) so power is always needed. Hence, the self-fulfilling prophecy and why everyone in my neighborhood is now putting in two pumps and a generator or battery backup. I kind of think the underground sewer with a check valve is a better option but overhead sewers are now required here.
Michael,
There are several issues all jumbled together here. A house won't flood unless the water table rises above the basement slab level. If that happens, you need drainage.
There are many locations in the U.S. where the water table never rises above the basement slab level. So it's not true that "all homes with sumps will flood."
If you want to remove water that is rising -- water that threatens to enter your basement -- of course you have to drain it. The traditional ways to do this are:
1. Drain to daylight.
2. If that's not possible, drain to a distant drywell located downhill from the house.
3. If that's not possible, drain to a sump.
Connecting a sump to a municipal sewer pipe isn't ideal, as you point out. In some areas of the country, it's still allowed, but it's not a great solution. Whether or not the municipal sewer pipe is installed below the elevation of your basement slab or above the elevation of your basement slab depends on local conditions.
If you have a city lot, the solutions that others have offered usually will not work. You cannot implement a pipe to daylight or dry well unless you have a ravine lot, as even a municipal storm water pipe won't be deep enough to drain your footing.
One other item that hasn't been discussed is that if is possible for groundwater and storm water to follow the utility trench back to your house. Because city sanitary sewers are often 12-14 ft deep at the road right of way, and given that these pipes are often back filled with clean stone, they essentially serve as French drains that collect water from the surrounding areas. Since your sanitary pipe is likely back filled with clean stone as well, the water can follow back toward your house. The correct procedure is to use a an earthen clay or bentonite dam over the sewer pipe to prevent this.
Secondly, if you are in clay soils, the ground can shrink away from your house in dry periods and create a gap at your foundation. If you don't have good pitch away from your house this can be a direct conduit to your basement. I disagree with Martin that most basement flooding problems are due to high water tables. It's typically poor grading.
Many times houses in older areas were set too low and there isn't much that can be done to correct drainage.
Basements are a hole in the ground waiting for nature to fill with water.
I disagree, but in my area 99 out of 100 homes have a basement. Done properly, they make a great rec area and/or extra bedrooms. Plus, they provide a level of safety from severe storms.
Rick,
Thanks for your response. I think its probably both of your issues, I did much to correct rain coming in to the foundation by the house with gutter extensions but it still got a fair amount of water when it rained. I know its not ground water as it was tested to 15 feed and bone dry.
It's also nothing that a sump can't handle easily in the normal course of things.
But the whole thing made me curious since it filled to 8" of water with only few days of heavy rain and no electric (the building was scheduled to be demolished) and I have never had water in any basement except for a building where the neighbor did not clean his gutter and the overflow ran right into a covered gangway with a door to the basement. (Obvious cause but surprisingly hard to fix if your neighbor is an %@%$##!!)
Rick,
Whether basements make sense is probably another one of those regionally specific questions. In temperate climates, where deep excavations aren't necessary, it's hard to make the case for adding that much area to the house in a location that yields such a poor quality of finished space, with so many potential downsides. While well-built basements can generally be kept dry, it's rare to find one that hasn't experienced some moisture problems, and the consequences of water infiltration is usually fairly severe.
In the areas in Western Canada that experienced catastrophic flooding during the past several years, the damage was almost entirely limited to the finished basements of the homes. Had they not been built with basements most would have been almost unscathed.