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  • Seepage Despite Working Sump Pump

    Hi - new to the forum so thanks in advance for any help. Four years ago I bought an 80-year old house and we put an addition on. Under the addition we dug a basement - this new basement is 3 feet lower than the basement for the old house. When the foundation was poured, the contractors laid exterior drain tile, which of course runs into a sump pit.

    This sump pit is very active, but the Zoeller pump does a fine job of emptying it. During heavy rains there is a constant flow of water into the pit.

    Originally, the upper part of the basement (the old basement) had no drain tile and no sump pump, so I had an interior system in stalled by basement systems (Chicago branch), and it works great.

    I'm getting seepage in the lower basement at the floor/wall joint - what's confusing is I'm getting it at portions of all 4 walls - even the wall that is interior and meets up with the old part of the house. The drain tile on the upper basement goes around the entire interior - so just above the lower basement, this tile runs the whole width of the house.

    This morning when I left for work, it was raining but there was just a trickle of water into the pit, however I had active seepage along all of the walls, and wetness on the settling cracks on the floor. I know the drain tile isn't clogged because I have a drain in a covered window well that I ran a hose into, and the water went right into the pit on the other side.

    So I'm pretty much resigned to the fact that the drain tile must somehow be laid improperly, and I'll need an interior system in this lower basement (which should be pretty easy because it's an unfinished rectangle). But for my own sanity I want to understand how this water is seeping in when my sump pit is filling very slowly, and I'm even getting seepage on an interior wall when the floor above it is bone dry. How is that water getting in when the wall doesn't touch the outside of the house? How is the other water making it past the drain tile which doesn't seem to be overwhelmed?

    I'm incredibly confused. Thanks.

  • #2
    Re: Seepage Despite Working Sump Pump

    Hydralic pressure? Are there Hairline cracks in the concrete floor?

    Comment


    • #3
      Re: Seepage Despite Working Sump Pump

      Originally posted by BrandonG View Post
      Hydralic pressure? Are there Hairline cracks in the concrete floor?

      There are some cracks on the floor - that's normal, isn't it? Nothing major, just settling cracks. House doesn't show evidence of sinking or shifting (windows and doors open and close easily, no bad nail pops), and it's been about 3 years since the addition was complete. The cracks get "wet" (the concrete darkens along the cracks), but the most evident seepage is along the floor/wall joint, and around the sump pit (which is not coming that close to filling up). There's even one section where enough water gets in to occasionally form a small puddle by the wall.

      I'm having the waterproofing co. that did the draintile on my upper basement take a look at this lower section.

      Comment


      • #4
        Re: Seepage Despite Working Sump Pump

        tj,
        is it possible that the perimeter drain tile for the new house is laid too high? It needs to be at the bottom of the basement foundation to be effective, and defenitely not above the wall/floor connection. If the drain tile is too high the saturated soil that is beneath the drain tile will provide water to the cracks. You may be able to dig down beside and exterior wall to confirm this. Also how deep is the pipe that flows into the sump? Can you tell if it is lower than the new basement slab. This could provide an indication of the elevation of the drain tile.

        Comment


        • #5
          Re: Seepage Despite Working Sump Pump

          Originally posted by nickbee View Post
          tj,
          is it possible that the perimeter drain tile for the new house is laid too high? It needs to be at the bottom of the basement foundation to be effective, and defenitely not above the wall/floor connection. If the drain tile is too high the saturated soil that is beneath the drain tile will provide water to the cracks. You may be able to dig down beside and exterior wall to confirm this. Also how deep is the pipe that flows into the sump? Can you tell if it is lower than the new basement slab. This could provide an indication of the elevation of the drain tile.
          Thank you Nickbee. When I had this addition built, I knew nothing about construction or waterproofing. After having my basement flood, and getting seepage on my upper (finished) basement before I had the interior system put it, I now know tons more. If only I could go back in time....

          I'm convinced the foundation subcontractor did an awful job laying the exterior drain tile. Looking back on it, as best I can recall from my visual inspection, I'm sure they just sprinkled some gravel on the ground, threw the pipe on top, and called it a day. I even remember the subcontractor arguing with my general that laying drain tile wasn't included in his bid - he was a real a$$. Unfortunately I didn't know enough to insist on a proper job, and while my villages' inspectors are sticklers for a lot of useless things (aren't they all?), they obviously blew this one.

          So, long story short - I bet your intuition is right. What else could it be? I know the drain tile isn't clogged. The pipe comes into the sump just below the basement slab, but I'll bet it's sloping steeply at that point, and is too high elsewhere. Really ticks me off. To be honest, I'd rather put an interior system in then excavate down to the footing to see where the exterior tile is. The interior system will provide an extra, and better, layer of protection, and is guaranteed for life. I've pretty much resigned myself to having to do that if I want to keep the addition dry. At least there is no finished work in this area at this point, so nothing to move around or tear out. I'm having an inspection done tonight by my local Basement Systems franchise (that installed my other interior system). I'll bet they reach the same conclusion you did.

          If I ever built another house, I'd use a waterproofing company for the drain tile, not the concrete company. Would have saved me a lot of aggravation.

          Comment


          • #6
            Re: Seepage Despite Working Sump Pump

            Originally posted by nickbee View Post
            tj,
            is it possible that the perimeter drain tile for the new house is laid too high? It needs to be at the bottom of the basement foundation to be effective, and defenitely not above the wall/floor connection. If the drain tile is too high the saturated soil that is beneath the drain tile will provide water to the cracks. You may be able to dig down beside and exterior wall to confirm this. Also how deep is the pipe that flows into the sump? Can you tell if it is lower than the new basement slab. This could provide an indication of the elevation of the drain tile.
            Nickbee -

            I tried several times to respond, but I'm getting messages that moderators need to approve. I guess the messages were too long? In any event, no moderator ever got back to me, but I did want to thank you for your response. Digging down isn't really an option I want to pursue - I have a deck on the back of the house and I'm not removing it even if I could determine the pipe was too high. The pipe that flows into the sump is below the slab where it enters the sump pit (wouldn't it have to be?), but I'm going to assume that before entering the pit, it must be too high, and I'm just going to add interior drain tile to keep the lower area completely dry. Seems like my best option at this point. I wish I would have known better when the original exterior tile was laid - I'm sure they did a lousy job.
            Last edited by tjkahn; 05-21-2009, 03:59 PM.

            Comment


            • #7
              Re: Seepage Despite Working Sump Pump

              One more question - in my upper basement, where I have interior drain tile, we had some pretty heavy rains in Chicago last week. I looked into the pit, and there was not water coming from the drain tile into the pit, but the water level in the pit was rising ever so slowly (pump cycled about every 10 minutes or so).

              Should I be concerned about this? How is water getting into the sump pit if it's not coming through the drain tile - and could that water find it's way past the drain tile somehow and end up on my floor?

              Comment


              • #8
                Re: Seepage Despite Working Sump Pump

                Originally posted by tjkahn View Post
                Nickbee -

                The pipe that flows into the sump is below the slab where it enters the sump pit (wouldn't it have to be?), but I'm going to assume that before entering the pit, it must be too high, and I'm just going to add interior drain tile to keep the lower area completely dry.
                You're welcome Tj. I would expect the pipe into the sump to be about 2 feet lower than the basement floor slab. The bottom of the foundation footing is probably about 18 inches below the basement floor. In a correct installation the drain tile would have been laid adjacent the bottom of the foundation footing over a thin layer of pea gravel. The pipe would be level around the building perimeter. At some point on the perimeter there would be a tee-connection and a drain pipe would slope away from the building to the sump at a slope of at least 1/4-inch per foot. So, unless your sump is clear over the other side of your yard, the incoming pipe should be around 2 feet below basement floor. If your yard is level and the basement is 6 feet below grade then the pipe will be 8 feet down.

                Installing the interior drain could solve the problem if the problem is a high water table; you said earlier that some water comes up through cracks in the floor - is this widespread? Maybe you should drill a couple of holes through the floor and see if any water comes out.

                Also make sure that the surface soil at the building perimeter slopes away from the exterior walls. You do not want any rainwater collecting and soaking into the soil at the basement walls. The drain tile will not collect all this water and some will end up coming through the wall joint.

                Comment


                • #9
                  Re: Seepage Despite Working Sump Pump

                  Originally posted by tjkahn View Post
                  One more question - in my upper basement, where I have interior drain tile, we had some pretty heavy rains in Chicago last week. I looked into the pit, and there was not water coming from the drain tile into the pit, but the water level in the pit was rising ever so slowly (pump cycled about every 10 minutes or so).

                  Should I be concerned about this? How is water getting into the sump pit if it's not coming through the drain tile - and could that water find it's way past the drain tile somehow and end up on my floor?
                  The drain tile and sump pump system is a groundwater removal system. Groundwater flow does not respond immediately to rainfall. It takes time for water to infiltrate into the ground and move towards the drain tile. This, of course, depends a lot on what type of soil you have - if your soil is sandy or gravelly and fairly permeable then water will move through it faster. Also if the soil surface around your house does not slope away from the exterior walls then rainwater will flow to the building and sink through the relatively permeable backfill around the walls. Make sure the dirt at the walls is dry! A slow response at your pump after rainfall is a good sign.

                  As for the water getting into the sump, there are probably some holes or gaps in the sump. If the sump is concrete then probably water is coming thorough gaps in the joints (for example a base and wall joint - sound familiar?). If the sump is plastic it may have holes that were drilled near the base to prevent floatation if the pump fails. I would not worry about this at all unless you see significant soil deposited in the bottom of the sump.

                  Water may be flowing inside the gravel bedding under the drain tile into the gravel backfill and up through the sump. Alternatively if a water table is rising due to rain, the sump is the lowest point in the drainage system and this will collect water first. Either way there is no problem and no cause for alarm.

                  Make sure that you service your pump regularly and consider keeping a generator to hook up to it if the power fails. Also if it is in a dry space - keep the lid on and watertight!

                  Another point, I am surprised you get much water in the upper sump as I would have expected the addition of the adjacent lower basement to have drawn away the water to its system.

                  Comment


                  • #10
                    Re: Seepage Despite Working Sump Pump

                    Originally posted by nickbee View Post
                    You're welcome Tj. I would expect the pipe into the sump to be about 2 feet lower than the basement floor slab. The bottom of the foundation footing is probably about 18 inches below the basement floor. In a correct installation the drain tile would have been laid adjacent the bottom of the foundation footing over a thin layer of pea gravel. The pipe would be level around the building perimeter. At some point on the perimeter there would be a tee-connection and a drain pipe would slope away from the building to the sump at a slope of at least 1/4-inch per foot. So, unless your sump is clear over the other side of your yard, the incoming pipe should be around 2 feet below basement floor. If your yard is level and the basement is 6 feet below grade then the pipe will be 8 feet down.

                    Installing the interior drain could solve the problem if the problem is a high water table; you said earlier that some water comes up through cracks in the floor - is this widespread? Maybe you should drill a couple of holes through the floor and see if any water comes out.

                    Also make sure that the surface soil at the building perimeter slopes away from the exterior walls. You do not want any rainwater collecting and soaking into the soil at the basement walls. The drain tile will not collect all this water and some will end up coming through the wall joint.
                    Thanks Nickbee. The water table is pretty high, and since the new basment is almost 3 feet lower I'm closer to it. I have really one main cracks in the floor, in the shape of a Y with two lines on the bottom instead of one. One line runs to the sump pit, the other to the wall on the other side. So the cracks run across the width of the floor and about 3/4 of the length. Water is not necessarily coming up through the cracks - the cracks get wet during heavy rains - you can see the concrete darken along the cracks.

                    I did have a clogged gutter for a little while over the winter and we got some heavy late winter rain. Water was spilling out of the gutter and puddling at the corner of the house (I know that's a really bad thing). Funny thing is the water that came in to the basement along all four walls, but none came in at the corner where the water was dropping. The biggest concern I have is along the wall where the new basement meets the old basement - it's an interior wall and on the opposite side from where the water was spilling over the gutter. That would tell me that water is getting past the exterior drain tile and making it's way all the way under the basement floor - even perhaps getting to the old (higher) part of the basement under the floor- could be another reason my upper sump pit was filling slowly (it's located at the rear conrner - very close to the new basment).

                    As far as sloping the property, I think my grading is adequate - but I live in an area where 6-8 feet on either side of the house is pretty typical, and my yard is no exception. The rear of the house is covered by a deck, and I've got downspout extensions on all of the gutters.

                    Thanks again!

                    Comment


                    • #11
                      Re: Seepage Despite Working Sump Pump

                      Originally posted by nickbee View Post
                      The drain tile and sump pump system is a groundwater removal system. Groundwater flow does not respond immediately to rainfall. It takes time for water to infiltrate into the ground and move towards the drain tile. This, of course, depends a lot on what type of soil you have - if your soil is sandy or gravelly and fairly permeable then water will move through it faster. Also if the soil surface around your house does not slope away from the exterior walls then rainwater will flow to the building and sink through the relatively permeable backfill around the walls. Make sure the dirt at the walls is dry! A slow response at your pump after rainfall is a good sign.

                      As for the water getting into the sump, there are probably some holes or gaps in the sump. If the sump is concrete then probably water is coming thorough gaps in the joints (for example a base and wall joint - sound familiar?). If the sump is plastic it may have holes that were drilled near the base to prevent floatation if the pump fails. I would not worry about this at all unless you see significant soil deposited in the bottom of the sump.

                      Water may be flowing inside the gravel bedding under the drain tile into the gravel backfill and up through the sump. Alternatively if a water table is rising due to rain, the sump is the lowest point in the drainage system and this will collect water first. Either way there is no problem and no cause for alarm.

                      Make sure that you service your pump regularly and consider keeping a generator to hook up to it if the power fails. Also if it is in a dry space - keep the lid on and watertight!

                      Another point, I am surprised you get much water in the upper sump as I would have expected the addition of the adjacent lower basement to have drawn away the water to its system.
                      This pump is much, much less active than the lower one. It only ever goes off during heavy rains. My lower pump can go off even every so often even when there hasn't been rain for days. The upper pump was added by me a couple of years ago when I was getting significant seepage during heavy rains (which of course the seller omitted from his disclosures). There's no backfill, per se, around this part of the house, which is 80 years old (the only outside digging for this system was for a portion of the drain tile to go outside around a finished bathroom), and my soil is predominantly clay.

                      Once the rain subsides, this pit gets no water - whatever is left below the float just sits there. The lid is screwed down and sits a couple of inches above the floot (it's a basement systems sump pit with two pumps - primary and battery backup).

                      I'm guessing that the water was rising in this pump because of what you mentioned above - water flowing inside the gravel bedding under the drain tile into the gravel backfill and up through the sump. That seems to make the most sense. I have the pump serviced every year by my basement systems dealer - I'll likely use them again to add the interior tile on my lower level, and put in a bigger sump pit.

                      My lower pump actually has a water powered backup on it - in case of a long power outage, I need to be ready since it's moderately active even with no rain.

                      Comment


                      • #12
                        Re: Seepage Despite Working Sump Pump

                        Well it looks like you are going to have to install that interior drain with yet another pump, this one inside the lower basement. The water seeping through the crack in the floor is not good, it will lead to mildew problems which is a major health concern, dank odors, ruined floor coverings etc. Presumably the floor slab is laid on gravel or sand so the water can move horizontally to the new collection trench. Install the new system and see if the situation improves. Then buy some sealant and seal all the cracks.

                        Your system seems to be pretty good – except it does not work well. The week link is probably the height of the lower drain tile as mentioned. Another possibility is poor quality fill against the wall – it should be sand or gravel against the concrete all the way down to the drain tile. Still I would not expect to see chronic seepage result from that.

                        Comment


                        • #13
                          Re: Seepage Despite Working Sump Pump

                          Originally posted by nickbee View Post
                          Well it looks like you are going to have to install that interior drain with yet another pump, this one inside the lower basement. The water seeping through the crack in the floor is not good, it will lead to mildew problems which is a major health concern, dank odors, ruined floor coverings etc. Presumably the floor slab is laid on gravel or sand so the water can move horizontally to the new collection trench. Install the new system and see if the situation improves. Then buy some sealant and seal all the cracks.

                          Your system seems to be pretty good – except it does not work well. The week link is probably the height of the lower drain tile as mentioned. Another possibility is poor quality fill against the wall – it should be sand or gravel against the concrete all the way down to the drain tile. Still I would not expect to see chronic seepage result from that.
                          Yeah, I obviously want to keep water off the floor, even though I don't plan on finishing this part of the basement for at least a few more years (I want at least 3 completely dry years before I do anything). I'm sure the floor sits on sand or gravel, I remember seeing it before it was poured, and even though my villages inspectors obviously did a lousy job inspecting the drain tile, I know codes in my village are pretty strict and they couldn't have screwed that up.

                          As far as installing the new system, won't that keep water from even getting under the floor? Obviously the interior system will be at the right height, so shouldn't the water be intercepted before it even gets to those floor cracks? (which I will just have the drain tile crew cement over when the put cement over the trench they dig into the floor) Nice thing is I'm 100% guaranteed against seepage on the floor for life, so if anything goes wrong they come back and fix it until it works 100%. I wouldn't expect anything to go wrong - they've got a pretty good reputation.

                          My plan is actually to replace the existing sump pit with a larger pit - what they call their "super sump" that can hold three pumps. I already have two - the zoeller I use as my primary is a great workhorse, and the water powered backup can handle over 600 gallons an hour (I've run a garden hose into the pit and it had no problem keeping up). But in reality the only time that pump was ever needed was when the sewer line filled up (my village lets you dump into the sewer, but I'm going to put a diverter on the discharge lines to dump water under the deck into the back yard in the event the rain overburdens the sewer). Before I finish the room I'd add the third pump.

                          I don't see a real reason to add another pump or pit at this point - just make the existing pit a little bigger. The waterproofing company agrees - do you have a different opinion?

                          Again, I really appreciate your help. Wish you were a little closer to Chicago!

                          Comment


                          • #14
                            Re: Seepage Despite Working Sump Pump

                            Yes, the new system should get the water before it gets to the cracks. Sealing them is just an added precaution. Not sure you can effectively cement over them unless you are pouring a slab of some thickness.

                            By all means use the existing sump, if it is deep enough to allow gravity flow from the new drain. The waterproofing company can check that with a survey level. It will mean a pipe penetration through or below the foundation. By bigger do you mean deeper? There should be no need to make it wider unless your pumps are cycling too frequantly and you need more storage.

                            Generally two pumps is enough unless you own stock in Zoeller. Ideally there would be a switching mechanism so the pumps can alternate. Otherwise one will seize up from lack of use.

                            Comment


                            • #15
                              Re: Seepage Despite Working Sump Pump

                              Originally posted by nickbee View Post
                              Yes, the new system should get the water before it gets to the cracks. Sealing them is just an added precaution. Not sure you can effectively cement over them unless you are pouring a slab of some thickness.

                              By all means use the existing sump, if it is deep enough to allow gravity flow from the new drain. The waterproofing company can check that with a survey level. It will mean a pipe penetration through or below the foundation. By bigger do you mean deeper? There should be no need to make it wider unless your pumps are cycling too frequantly and you need more storage.

                              Generally two pumps is enough unless you own stock in Zoeller. Ideally there would be a switching mechanism so the pumps can alternate. Otherwise one will seize up from lack of use.
                              Nickbee -

                              Thank you for continuing to engage me in this discussion - sorry I didn't respond sooner as I've been away from internet access for a few days. With respect to the size of the pit, I think it will be wider only because the "triple safe" sump that basement systems dealers install are a little bigger than the standard size pit I currently have, primarily so it can accomodate three pumps. I don't think it would hurt to have more capacity as my pump does cycle quite frequently. For example, last night we had heavy storms and during the peak of the sump pits activity, the pump was cycling on more than it was off (about a 10-15 second cycle on time, followed by 10 seconds off). I'll tell you, the zoeller pump I have is a great product - it's been in the pit for almost three years, and it can cycle like this during heavy rains. Even without rainfall it rarely has a down day during spring and summer months. I'm also impressed with my water powered backup. I generally test it's functionality during a heavy rain by unplugging the zoeller - last night, when the zoeller was going off 6 times or more per minute, the backup also emptied the pit (it took a little longer, but the water level went all the way down). Definitely provides some peace of mind.

                              With respect to sealing the floor cracks, could I just do that myself by running some silicone over them and smoothing it out?

                              Interesting that with all the rain last night (my 1.75" rain gauge filled up), I got almost no seepage on my lower level - the floor cracks did not sweat, and the only areas that had very minor new seepage were the cold joint right next to the sump pit, and a tie rod that leaks slightly on occaision (not enough for the water to get to the floor). I'm not sure why some rains trigger more seepage than others - the rain last night got pretty heavy for a couple of hours. Usually that tie rod is the last thing to leak. Strange. I'm sure now that my downspout is unclogged it's making a big difference.

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