Water, Water Everywhere And Not A Drop To Drink

March 12, 2011 5:24 PM

After having drainage and a sump pump installed in our basement, we’ve noticed an unusually large amount of groundwater being pumped out into the connecting dry well. We’d like to determine the source of this water, but, as usual, there are some unusual details….

A few years ago, after noticing light flooding in the basement after rainstorms, we had a contractor come in and construct a proper drainage setup with a sump pump leading to a dry well. For the past two or three months we’ve noticed, on average, that the sump pump pumps for about six seconds every two or three minutes, whether it’s raining or not. (Note: It has ALWAYS pumped since installation, but it seems to have increased in frequency lately.) That seems like a ridiculously high amount and we’d like to determine the source of this water coming in. Here are what seem to be the relevant details:

· We live midway up a hill, at the top of which is a covered reservoir used for the city’s water supply. Several years ago there was construction done in and around the reservoir (although I have no idea what exactly was done. I just saw the construction vehicles.)

· Thinking the source of this water might be a leak from the reservoir, we took a sample of the groundwater and had it tested for fluoride content, which came back negative. We have heard (although can't confirm) that the reservoir is the point where the fluoride is added. It's possible that the fluoride is added as the water is pumped out of the reservoir and thus we wouldn't have detected it, however there were also tests for other chemicals which might be found in city water, all with negative results.

· Several neighbors on our side of the street also have problems with excess water. Water seeps (very slowly) through cracks in driveways (especially noticeable in winter when it ices over) and a few neighbors have pumps going out into lawns or dry wells. Neighbors across the street don’t have problems with excess water but they DO have issues with their houses settling unevenly.

· The city (Newton, MA) has steadfastly denied that there is anything wrong with the reservoir and has instead blamed it on an underground river. While I have never seen any proof that such rivers exist, I have heard in the course of conversation with other city residents that there are apparently a number of them scattered around and that flooded basements are not uncommon among city residents as a result.

Does anyone have any ideas how we might determine the source of this water coming in? Are there services that can be hired to do this, or would these “rivers” be located on city maps? This has only been a problem within the past ten years, apparently. Prior to this, water would come in under extreme circumstances (very heavy rains for an extended period) but otherwise the basement remained dry. Any thoughts would be appreciated.

posted by Rewind to home & garden (7 answers total)

The first question to ask regarding these underground rivers: is there any surface water nearby? Where are you in relation to the water table? (image)
posted by slidell at 5:42 PM on March 12, 2011

I think there are two likely possibilities. One, there is some sort of leak either at the reservoir or there is an underground river. I am not an expert on the underground river and the first time I heard of one I envisioned sort of a cave with a river. It is not like that. I am told that it is more of an area where water flows through the ground and there are often spaces where rocks have formed underground gaps. Or, look at it this way, the ground water level near your house is real high.

My next door neighbor who lives slightly down hill from me and I am slightly downhill from the other side had significant water issues for a little while in his basement and dugout garage. I only had water in my basement when there was one of those 50 year rains that happen every 5 years or so. Anyway, for a while he was working with me and my gutter drains. I tried redirecting and doing all sorts of things. He kept asking the town about leaks in the water delivery pipes. They denied. Finally, one day about a year ago, there was a sinkhole formed in the street up about 6 or seven houses uphill. Turns out there was a water leak and it was going for a long time.

We wondered why they didn't notice they were sending more water this way than they were billing, but it is obviously much more complicated than that. I can imagine that there is some sort of leak in one of the pipes from the reservoir and the town does not even know it. I have no idea how you can get Newton to actually search for one.

I also think it could be both a high water table and a slow leak from the reservoir.

If the city is so sure there is an underground river, they must have documentation or maps for these rivers. Go to the historical society and see if there are any old maps that identify rivers or streams near or at the location of your house.
posted by JohnnyGunn at 5:42 PM on March 12, 2011

is there any surface water nearby? Where are you in relation to the water table?

There's no other surface water nearby, although there is another unused reservoir (this time open air) up the street and - position wise - a tad further down the hill. I discounted that as a possibility, however, simply due to where it is. If it had a leak, the water would (in theory) continue to flow downhill away from the house. Unfortunately, I have no idea where we are in relation to the water table (I'm kind of a novice at these things, as you might have guessed) and am not sure how I would find out.
posted by Rewind at 7:05 PM on March 12, 2011

A hydrogeologist could tell you more about the local water table. Hills tend to be the sort of place where you see seeps - think of springs coming out of mountainsides. Also, as a local, I know that people all over the region have a fair amount of water in their sumps (or little rivers flowing across their field stone basements), especially this year because of all the precip we've had - the water table is High right now. In general the water table doesn't tend to be very far below ground surface in eastern MA and my coworkers in areas as diverse as Milton and Holliston have complained about sump volume this year.

However, the fact that you believe you've seen an increase over time is a cause for concern. I would contact the contractor that put in the sump first, just to be sure it's running properly (this may be as simple as a phone call). If it seems that your sump is working well, try an environmental consultant (maybe the one that did your water analysis). I can't recommend anyone in the area, but I do bike past Geohydrocycle on my way home from Newton all the time.

Lastly, and this is pure speculation, I would be surprised if it's the reservoir above you that's directly the problem. The MWRA has gotten very good at tracking leaks because they cost them money. But there might be other changes to investigate.
posted by ldthomps at 8:28 PM on March 12, 2011

The sump pump behavior you describe matches mine. I installed mine in anticipation
of water problems in the excavation that held the sump for the sewage ejector.

In my case, the pump is designed to come on every 2 or 3 minutes, and to pump
until the water is pumped out, at which point the motor overspeeds, the current
draw goes up, the circuitry in the pump detects the overcurrent, and shuts it down.
Then in 2 or 3 minutes, the cycle repeats. The pump will do this even when there
isn't anything to pump. It prevents the pump from overheating and wasting power
when it is dry, and guarantees that the pump will empty any water that does
accumulate in the sump when there is actually water to pump.

To see if the pump is actually pumping anything, put the end of the outflow into a
bucket of some sort, and check it once a day to see if it has pumped anything out.
Or hang an open-topped tin can below the outflow of the pump into the dry well,
so that you can see if water is actually being pumped. You should also be able to
peer into the sump where the pump is to see if there is actually any water in there.
You might be able to pull the pump up and down, on the drain hose, to see if you
can hear any splashing.

The idea is to verify that there is actually water being pumped out.

It could very well be that you are being fooled by the automatic behavior of the pump.
It could be that the pump is coming on every 2 or 3 minutes not because there is
water to be pumped out, but because it is designed to do so in case there is water
to be pumped out.

Who is the manufacturer and what is the model number of your pump?
posted by the Real Dan at 11:39 PM on March 12, 2011

Thanks for all the great answers so far, folks. much appreciated.

the Real Dan: Hadn't thought of that and will definitely check it out. I'm not sure of the manufacturer of the pump as it was installed by the contractor who put together the whole setup in the first place. He's coming back to install a backup pump and battery system (we were worried about exhausting the current pump) and I'll be sure to ask him about it. The current pump is most certainly pumping water though, and lots of it. One of the things that caused me to ask this question in the first place is that the pipe underneath the lawn connecting sump to dry well appears to be blocked (another reason the contractor is coming out) and so we've had to redirect the flow of water so that it's now being pumped out through a garden house and onto the lawn. I used the garden hose to see how much water one pump would fill of a 2 or 2.5 gallon bucket (the label was ripped off and I couldn't tell which size it was) and it came only about an inch from the top.
posted by Rewind at 8:47 AM on March 13, 2011

Possibility: the water table is high. It is below the floor of your basement most of the time, unless it rains a lot. You dug a hole in your basement to fit the sump pump, and the bottom of that hole is below the "surface" of the water table. You are pumping mostly harmless water.

If that's the case, you should be able to shut off the sump pump and watch the hole fill with water and then stop at some level. If THAT happens, just set the on-off float above that level.

They did an Ask This Old House segment that sounds exactly like this. It might even have been in Newton.
posted by gjc at 1:11 PM on March 13, 2011