High water table - will interior perimeter drain tile help?

[John_7951]

This might be a question for a hydrostatic engineer, but I figured I'd start here. Bottom line - I have a high water table under my house. This is consistent with soil boring samples I had done a few years ago. I've opened up the concrete floor in the half basement and crawlspace slab to put in a floor drain. The water level is about 2-3 inches below the thin slab in the crawl space. It's a little higher in the half basement interior side - higher than the crawlspace level. I'm not sure how that is possible but I think the footings are acting as a barrier and collecting more water in the living space side. The half basement is closer to the back yard where the water may be coming from.

I don't have what I would consider a bad dampness problem. The crawlspace gets some dampness at the edges of the slab. The basement is usually dry. There was some intrusion a few years ago when we had a really damp spring.

My question is this - I can pay 10's of thousands of $$$ to have interior perimeter drain tile installed - but will I just end up draining the water table in a futile attempt to empty it? Will I just end up running my sump pump constantly for no real effect - or will the ground eventually dry out under the basement? My house is about 3 feet lower than my neighbors to the east. The ground slopes down to the west over the course of about a mile to the east branch of the DuPage River (Naperville Illinois).

The house was built in 1968 and has 4" clay drain tile on the outside perimeter.

Thanks for any thoughts, advise or directions on where to go next.

John

 

[Crashcup]

John, I'm no expert, but I guess that's not stopping me from commenting....

That sounds strange that the water table would be that high. I thought "water table" meant the level of water that corresponds to the water level in a nearby body of water. In other words... the water table would not go down unless the level the river actually goes down. If that meaning of "water table" is correct, why would they have built a house at that elevation where the water table is just under your slab?

Do you have access to observe the drainage from your outside drain tile? If so, does that always have water draining? I would think if the water table is truly that high, and the exterior drain tile is always draining water, the same would be true for interior drain tile.

Or maybe the exterior drain tile is overwhelmed, or clogged, and the addition of interior would add more drainage capacity?

I'd be curious to see if there are any public surveying records that would show what the elevation difference is between your lot and the river's OHWM. And it might be a good idea to have someone qualified take a look at the exterior drain tile to see if that can be improved somehow. (Unfortunately, it seems like there's a lot of fly-by-night operators who flock to that basement drainage work).

 

[Sponsor]

 

[Reach4]

The house was built in 1968 and has 4" clay drain tile on the outside perimeter.

How much water is that foundation tile system delivering to your sump?

 

[John_7951]

I have a couple of guesses about the situation ...

I think the water table is a localized effect. I have clay in my area. I think the fact that I'm on a gentile slope down towards a river creates a stratified soil structure where I get the water "pooling" below me as it works its way down and out towards the river. Just a wild guess. If I can find my soil test, I can get the specific soil description (they have names which mean nothing to me).

I had the occasion to replace one portion of the exterior drain tile last year. I was building a deck and did not want to rely on the tile that was there going forward (south side). I had planned to replace more of the exterior tile in a few years but I didn't realize I had this much water at the time. The top of the existing clay tile is even with the top of the footings. It was made from 2 foot sections with a gap between each. I think it had broken tile pieces over the top (not sure if it had tar paper too). It was generally clear but had some silting. The perimeter drain tile terminates in the sump pit and does not have any exit away from the house.

The amount of water coming in through to the sump pump seems "normal". In rain, it may run every 5 minutes. After the rain stops, it slows down to every 15-20 minutes after a few hours. In dry summer, it runs infrequently. The situation seems to be that the water table is just a few inches below the drain tile so that there is always water that doesn't get channeled to the sump pit.

I'll upload a pic or two ...

 

[Reach4]

When you dug through the basement floor, you should have hit a layer of gravel. With construction today, it would be crushed stone, but yours might have been pea gravel. Pea gravel passes water better, but is not as strong. I would think you should have cut through steel reinforcement wire embedded in the concrete.

What I would do is to bury a sump pit liner. You might want the stronger type used for sewer pits, but you will not need to seal your system. A deeper pit is better if you can do the digging, because it lets the pump run less often. You would have to deal with the water as you dig. When placing the liner, you would weight the liner, possibly by filling with water. Fill the area around the sides with pea gravel. Drill staggered 1/4 inch holes in the liner at the height of the gravel under the concrete and a little lower.

Cement the liner into place with concrete or mortar mix. Mortar does not have the aggregate, so it fits into smaller clearances. Pump out the water with another sump pump.

This would supplement your perimeter drain system.

Is there a tree that might have clogged your perimeter drain pipe with roots? It would be interesting and maybe useful to run a Clog Hog through your perimeter drain the next time you have access.

 

[John_7951]

No wire reinforcing mesh in basement side slab - no visqueen - about 5-6 inches thick concrete depending on location. There is about 2-3 inches of crushed limestone under it. In the crawlspace, it's just 2-3 inches of concrete over the clay dirt. It's generally an inch (+/-) below the top of the footing, or even with it

.

I have to replace the sump liner. Its on the very south west of the crawlspace. It doesn't seem to be as wet there. Or doesn't seem to help all the water on the north much. It's an old vitreous china liner - cracked and loose fitting tile coming into it. I'm wondering if running a limited run of 4" sdr-35 perforated tile to that location would help - a little? a lot?

The quotes I got to do the perimeter rectangle of the crawl + basement ranged from $8-10K. I hesitate to commit to that if it is never really going to dry out much.

 

[Reach4]

I don't see the liner in your last picture. That pump is very high, and I wonder if that system is not the provider of the water under the floor.

I would aim at a 36 inch deep basin.

A limited run of perforated pipe would definitely improve collection. Instead of perforated SDR-35, I would use schedule 40 with a big bunch of 1/4 inch holes. It is stronger, and your gravel will not fall into the holes. You can drill about 10 holes per minute. It might be overkill, but relative to the efforts of the rest of the project, it is minor. If you do use pipe with big holes, cover it with a drain sleeve AKA filter sock.

You would want the pipe surrounded by gravel.

 

[Standardairconditioner]

I have a high water table under my house.

You're in luck, so does every Canadian that lives along the St-Lawrence river, a freshwater artery that feeds the Atlantic.

You'll never get a "dry floor". That's because it's always being supplied "wetness" from mother nature and geology.

So what do the Canadians do?

There are many words for it, but in general you want a French drain for your home. They have been built since the French have been settling in Canada, long before the Mayflower days.

Without repeating too much of what you can search on your own, in a nutshell it is an EXTERIOR overflow drain system that is installed at your basement floor level or below it, and will take away any rainwater from above its install or ground water from below its install, and drain that either directly to your home main or a dedicated drain to the street main.

You must dig all around your home like a moat, down to the floor level of your basement floor, this is where the drains are dropped.

Since you have all the exterior walls of your basement exposed, at the same time we take the opportunity to waterproof the walls, stopping moisture absorption to a dead stop. Bye bye humid basements, or need for dehumidifiers.

French drain systems are rarely installed on the INTERIOR inside perimeter of the basement, mostly because it doesn't cost any less, and deprives the homeowner a chance to waterproof the walls, which can only be done from the outside.

Cover it all back up, and you will see you will never ever run your sump pump, ever again.

How does it work?

When it rains, rain gravitates down, just like you are watering a flowerpot (without holes in it). Eventually the rain hits a water table (the bottom of the flowerpot without holes), and now the rain starts collecting up. Once the rain collects high enough to run into those new french drains you installed, it all flows away, thus, impossible for rain to collect above your french drain.

Some Canadian contractors have a great amount information and diagrams out there, videos explaining the entire job process and how it works (your high school french lessons will reward you here). Many of them roll the red carpet for you if they think you will be a client. You can call many of them to get a wealth of information, just don't ever tell them you are a non-national just fishing in their waters

 

[John_7951]

Some more information ...

Reach4 - The picture with the sump pump is the hole I dug in the crawlspace for the drain. The depth beneath it is maybe 3 inches below the bottom of the footing. It's not the sump pit. My plan is to dig under the footing and run 3" schedule 40 from the basement out to that hole - then on to the sump pit. The other picture shows the hole inside the basement. The third shows the relative height of the water levels (not very clear). I have not dug out the dirt from the inside to the outside yet, so the water levels are not equal in height.

The idea of drilling holes in sched 40 makes sense. I'm not sure if that will pass inspection for this run to the sump pit (tho it won't be very visible after bedding in pea gravel)? I would also want to put a filter sleeve over it if there is something that fits sched 40 vs sdr-35.

Standardairconditioner - The use of a French drain is something I've been considering. I've done some landscaping in the yard to add swales to the north and some 6" drain tile about 20 feet from the house on the east and south sides of the house running to the drainage ditch in the front of the house. But this is surface drainage and not down at the level of the water table where a French drain should be. I think all that I have done has helped. The basement has not gotten water in the last two years since doing the work and I think we have had heavy rains like when it got water before (2009?). But this is hindsight. I didn't know then about the water just under the slabs.

What is the effectiveness of French drains if situated away from the house? I have two air conditioners and the main sewer line running along side the basement. The estimates go up $5k to do the perimeter drains on the outside foundation - plus the cost to disconnect/reconnect the A/C condenser units, etc. Can French drains be done 10 feet from the foundation (or so) and be effective?

Another question I really need to find the answer to is related to the picture you attached. If my water table is 3 inches below the interior French drain tile, what will I really achieve. The interior tile would drain water at its level, but wouldn't there still be water below the tile? If I don't have a "severe" water/dampness problem now - with the water 2-3 inches below the slab - why spend the money?

Thanks to all for your feedback!!!

 

[Standardairconditioner]

The picture I attached is just a random pic I found, and was not specific to your case.

French drains are only effective when they hug the foundation walls.

The main reason is that the entire ground is effectively a big SPONGE and if you move your french drain system away from the house, all you'll do is have some rabbits and badgers may thank you for keeping their home dry, and water will still "soak" its way towards your basement.

French drain installs are an industry of it's own, and is FAR SEPARATED from plumber folks. Would be comparing an auto mechanic and an aerospace mechanic.

French drain business in Canada is vertical and it's all they will do, and there are just as many of them here like lawyers in your U.S. yellow pages. I don't know how vast or limited this may be in your area.

Like I said, these folks roll out the red carpet for you because of the sheer amount of money involved, so if you want a warm and personalized Q&A session, get one to visit your home and you can get all sorts of pretty phamplets you can study, even if you have no intention of doing business with them. This matter is too complex to be generalized in a forum thread.

 

[hj]

All that would happen if you installed drain tile is that your pump would try, very unsuccessfully at that, to drain the ENTIRE water table until it was below your tile.

 

[Cacher_Chick]

I can understand what you believe you are seeing. It is not really the water table, it is the fact that your basement was dug in soils which are primarily clay. This clay passes water through it very slowly, so the hole excavated for your basement will retain water like a swimming pool.

The first things you need to do to improve the situation is make sure that you have properly graded the soil surrounding the home so that surface water runs away from the foundation. Some people install a graded clay cap or use plastic sheeting under the final layer of topsoil to force all water to run away from the area of the foundation.
Next, make sure you pipe all storm-water from gutters and the sump pump to the downhill side of the foundation, with the discharge at least 30 feet away from the foundation. If you have an uphill side to the property, this is where a french drain can be installed to redirect water flowing horizontally from the uphill side.
Finally, get your sump basin fixed so that it maintains the water level at least a few inches below the floor. Pumping the water lower that this is only wasting power and shortening the life of the pump, with little or nothing to gain. The water will dry up during the dryer months of the year, but the sump pump is the only thing preventing your clay swimming pool from filling entirely during a major rain event.

 

[Jadnashua]

The house I grew up in is about 1/4-mile from the town's spring fed water supply. Needless to say, the water table is fairly high around here. The sump pump needs to run fairly often, and things can get dicey quickly when the power goes off! It was not unusual while I was growing up if the power was off for more than an hour or so for the water in the basement to rise as much as 6". It was relatively flat, so no place to drain things downhill. You must try to keep as much rainwater out of the basement as you can, and then deal with the ground water the best you can.

 

[hj]

when I lived in a Chicago suburb, the water table was only 9" below the basement floor, AND it was in a layer of "running sand" similar to quicksand. The sand and water would fill the sump pit and surround the pump so it could not remove the water.

 

[John_7951]

Well, it's coming on a year and I'm just now getting close to framing my basement - after doing a lot of work throughout the house. I thought I would give an update on the drainage for anybody who's interested.

In the basement, I installed the floor drain and trenched to run it 25-30 feet in the crawl space - into a new sump basin liner and pump. As part of that, I used perforated 3" schedule 40 pvc in two locations. The first place was just inside the basement side of the footing for about 3 feet from the floor drain. I set it deep - below the level of the footing. I used a filter sock over the pvc, embedded it in pea gravel - wrapped with 4 oz filter fabric.

I did a similar run at the head an old trench in the crawlspace where I found 2" pvc had been installed by a previous owner. My new perforated section ran for a couple feet from the corner near the footing where a "gap" was in the footing that allowed "some" water to drain from the basement slab side into the crawl side. The two perforated sections met and ran south to the new sump basin.

In addition, I hired a plumber to rough in new waste lines for the bath on the other (east) side of the basement. He also was going to put in a new septic ejector basin in the crawl to replace the crummy one that was there. After he had busted up the concrete and trenched for the sewer lines, the trenches filled with water like a swimming pool to just about the bottom of the slab. The plumber had to put a temporary pump in the old ejector pit to keep the water draining. The trenches filled and drained constantly. It finally slowed by the following day - but the water flow was pretty constant at that point. I interpreted that to mean the swimming pool that was formed by the footings drained after a day, but that new water was still entering from the yard outside.

This made me re-think the effectiveness of the "fix" I did as part of putting in the floor drain - it wasn't. The other thing it showed me is that the water coming in was much heavier on the east side of the basement where the rough-in was going in. That is the higher side of the yard. The water that was coming in near the floor drain was not as heavy. I took that to mean that the water could not flow very easily between the clay (no gravel) and the slab. In the trenches, it was different. Water was coming in from the outside and was not impeded by the clay/slab boundary so it could just flow in all day long. I was concerned that it would drain for weeks/months/years until it effectively drained the higher yards to the east - if ever.

Bottom line - I decided to ask the plumber to dig/install yet another sump pump and to run perforated drain tile along the footing that was now accessible along the east wall. The trench along that wall ran for about 8 feet inside the basement side. The trench in the crawl side was another 5 feet leading to the new sump pit. It's all I could do given the time/budget constraints, so I went with it.

Well, it seems to have worked. Eventually (couple weeks), the constant flow stopped and now it's just a trickle during dry periods. When it rains, it seems to be very effective at catching the water and getting it out. It runs and pumps all day long - then slows back down to a trickle a few hours after the rain ends.

Two side effects seemed to have resulted: (1) The hairline cracks that were in the slab before now seem more pronounced and have become slightly more jagged (in feel) and chips have broken out. I assume the slab has settled some minute amount now that the hydrostatic pressure has been reduced(?) (2) The ditch at the street, where all the sump pump water goes, is now constantly soggy - even in the height of summer. It used to dry out after spring and a few days after a rain - but not now. It has not dried out since the new sump pump went in 8 months ago. I think I actually am draining all the yards to my east - and probably will do so forever.

Thanks much for everyone's help!!!

 

[darkim]

I

Well, it's coming on a year and I'm just now getting close to framing my basement - after doing a lot of work throughout the house. I thought I would give an update on the drainage for anybody who's interested.

In the basement, I installed the floor drain and trenched to run it 25-30 feet in the crawl space - into a new sump basin liner and pump. As part of that, I used perforated 3" schedule 40 pvc in two locations. The first place was just inside the basement side of the footing for about 3 feet from the floor drain. I set it deep - below the level of the footing. I used a filter sock over the pvc, embedded it in pea gravel - wrapped with 4 oz filter fabric.

I did a similar run at the head an old trench in the crawlspace where I found 2" pvc had been installed by a previous owner. My new perforated section ran for a couple feet from the corner near the footing where a "gap" was in the footing that allowed "some" water to drain from the basement slab side into the crawl side. The two perforated sections met and ran south to the new sump basin.

In addition, I hired a plumber to rough in new waste lines for the bath on the other (east) side of the basement. He also was going to put in a new septic ejector basin in the crawl to replace the crummy one that was there. After he had busted up the concrete and trenched for the sewer lines, the trenches filled with water like a swimming pool to just about the bottom of the slab. The plumber had to put a temporary pump in the old ejector pit to keep the water draining. The trenches filled and drained constantly. It finally slowed by the following day - but the water flow was pretty constant at that point. I interpreted that to mean the swimming pool that was formed by the footings drained after a day, but that new water was still entering from the yard outside.

This made me re-think the effectiveness of the "fix" I did as part of putting in the floor drain - it wasn't. The other thing it showed me is that the water coming in was much heavier on the east side of the basement where the rough-in was going in. That is the higher side of the yard. The water that was coming in near the floor drain was not as heavy. I took that to mean that the water could not flow very easily between the clay (no gravel) and the slab. In the trenches, it was different. Water was coming in from the outside and was not impeded by the clay/slab boundary so it could just flow in all day long. I was concerned that it would drain for weeks/months/years until it effectively drained the higher yards to the east - if ever.

Bottom line - I decided to ask the plumber to dig/install yet another sump pump and to run perforated drain tile along the footing that was now accessible along the east wall. The trench along that wall ran for about 8 feet inside the basement side. The trench in the crawl side was another 5 feet leading to the new sump pit. It's all I could do given the time/budget constraints, so I went with it.

Well, it seems to have worked. Eventually (couple weeks), the constant flow stopped and now it's just a trickle during dry periods. When it rains, it seems to be very effective at catching the water and getting it out. It runs and pumps all day long - then slows back down to a trickle a few hours after the rain ends.

Two side effects seemed to have resulted: (1) The hairline cracks that were in the slab before now seem more pronounced and have become slightly more jagged (in feel) and chips have broken out. I assume the slab has settled some minute amount now that the hydrostatic pressure has been reduced(?) (2) The ditch at the street, where all the sump pump water goes, is now constantly soggy - even in the height of summer. It used to dry out after spring and a few days after a rain - but not now. It has not dried out since the new sump pump went in 8 months ago. I think I actually am draining all the yards to my east - and probably will do so forever.

Thanks much for everyone's help!!!

Well, it's coming on a year and I'm just now getting close to framing my basement - after doing a lot of work throughout the house. I thought I would give an update on the drainage for anybody who's interested.

In the basement, I installed the floor drain and trenched to run it 25-30 feet in the crawl space - into a new sump basin liner and pump. As part of that, I used perforated 3" schedule 40 pvc in two locations. The first place was just inside the basement side of the footing for about 3 feet from the floor drain. I set it deep - below the level of the footing. I used a filter sock over the pvc, embedded it in pea gravel - wrapped with 4 oz filter fabric.

I did a similar run at the head an old trench in the crawlspace where I found 2" pvc had been installed by a previous owner. My new perforated section ran for a couple feet from the corner near the footing where a "gap" was in the footing that allowed "some" water to drain from the basement slab side into the crawl side. The two perforated sections met and ran south to the new sump basin.

In addition, I hired a plumber to rough in new waste lines for the bath on the other (east) side of the basement. He also was going to put in a new septic ejector basin in the crawl to replace the crummy one that was there. After he had busted up the concrete and trenched for the sewer lines, the trenches filled with water like a swimming pool to just about the bottom of the slab. The plumber had to put a temporary pump in the old ejector pit to keep the water draining. The trenches filled and drained constantly. It finally slowed by the following day - but the water flow was pretty constant at that point. I interpreted that to mean the swimming pool that was formed by the footings drained after a day, but that new water was still entering from the yard outside.

This made me re-think the effectiveness of the "fix" I did as part of putting in the floor drain - it wasn't. The other thing it showed me is that the water coming in was much heavier on the east side of the basement where the rough-in was going in. That is the higher side of the yard. The water that was coming in near the floor drain was not as heavy. I took that to mean that the water could not flow very easily between the clay (no gravel) and the slab. In the trenches, it was different. Water was coming in from the outside and was not impeded by the clay/slab boundary so it could just flow in all day long. I was concerned that it would drain for weeks/months/years until it effectively drained the higher yards to the east - if ever.

Bottom line - I decided to ask the plumber to dig/install yet another sump pump and to run perforated drain tile along the footing that was now accessible along the east wall. The trench along that wall ran for about 8 feet inside the basement side. The trench in the crawl side was another 5 feet leading to the new sump pit. It's all I could do given the time/budget constraints, so I went with it.

Well, it seems to have worked. Eventually (couple weeks), the constant flow stopped and now it's just a trickle during dry periods. When it rains, it seems to be very effective at catching the water and getting it out. It runs and pumps all day long - then slows back down to a trickle a few hours after the rain ends.

Two side effects seemed to have resulted: (1) The hairline cracks that were in the slab before now seem more pronounced and have become slightly more jagged (in feel) and chips have broken out. I assume the slab has settled some minute amount now that the hydrostatic pressure has been reduced(?) (2) The ditch at the street, where all the sump pump water goes, is now constantly soggy - even in the height of summer. It used to dry out after spring and a few days after a rain - but not now. It has not dried out since the new sump pump went in 8 months ago. I think I actually am draining all the yards to my east - and probably will do so forever.

Thanks much for everyone's help!!!

i recently purchased a home with the same problem you reported a few years ago. As I researched remedies to this problem, I stumbled across your post and thought I’d ask if your previous water problem is still fixed? Or did it find its way back again?