Weeping tile installation
kesheshian
| Posted in General Questions on
The plans on my new house call for my footings to be 18 inches below the level of my basement floor. High water table and the engineer wanted the footings on undisturbed soil. So I basically need to pour my basement wall 18 inches higher then plan then fill the inside with crushed gravel and have my basement floor elevated. How should I install my perimeter weeping tile? I obviously cannot have it that far below my basement slab or I won’t be able to access the sump pump/pit. Thoughts? Should I suspend the weeping tile outside the wall just below the basement slab? Thanks.
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Replies
kesheshian,
The place for the weeping tile is beside your footings. Don't worry about the depth of your sump pit. It's not unusual to have them three or four feet deep. Pulling a pump from that depth is easy..
I’ve seen 8 foot deep sump pits before. Typical is more in the 3-4 foot range as Malcolm mentioned. You absolutely don’t want to compromise your drainage just because you want to keep the sump pit any particular depth.
Set the drain tile next to the footings so that it is sitting at the level of the bottom of the footing. This way you have no pooling water in the lower part of the basement wall since the drain is always at the lowest point. Set the sump pit as required to get all the drains pitched properly. If you end up with a sump pit too deep for you to reach the pump with your arm, tie a rope to the pump and tie the rope off above the level of the sump pit where you can easily reach it. Install a Union in the drain pipe going down to the pump and put the Union somewhere above the level of the slab where it’s easy to access. This will make any pump maintenance or replacement much easier and will make sure you don’t have to use the pipe to lift the pump which is always a bad idea.
Bill
Bill,
Several decades ago I watched two idiots lower a third into a septic tank to undo a union located a foot above the pump. Once they were done I suggested moving the union up to the top of the tank. They were quite appreciative of the advice - especially the one who had garbage bags duct-taped to his clothing.
Kinda reminds me of a story my mom told me from when she was a kid. Her neighbor was looking into the septic tank while they were getting ready to pump it out. She remembers seeing her neighbor fall in and then standing in the full septic
Tank holding his beer up above the sewage. I doubt I will ever forget that story...
Anytime you build anything that needs service it’s worth thinking “what can I do to make the service work easier?” A few minutes and maybe even a few dollars at construction time can be an a godsend later when something breaks.
Bill
kesheshian,
If you have a known water table situation it will be important to have the footing drain properly set next to the footing not on top in the corner formed by the wall/footing intersection. If you let them put the drain line on top of the footing, you will be ensuring the presence of water for the full depth of the footing. (and perpetually wet footings) If a capillary break for the wall/footing bond has not been specified, then the wall will dutifully pull dampness up from the footing. Their is some controversy over capillary breaks, so search the GBA questions with that term. Discuss with the engineer and cement contractor now.
I may sound like a terminology bug, but crushed gravel may not be what you mean or want. If you mean something like crushed rock with fines included, then you will be building in a potential sponge mat under the slab. The material will need to be compacted in lifts as well to ensure a stable base. If you actually mean crushed stone, specify washed stone for at minimum 2", better 4" of the final depth under the slab. Some differences of opinion on the need to compact stone, so check. On soft sub-soils it will likely need at minimum a first layer done.
Depending on where you are able to direct your drains, hopefully to open air, placing interior footing drains, which connect to the outside is a good path toward maintaining as dry a condition for the foundation as possible. If you are having to rely on the sump pump to lift and eject, stop and consider how to avoid creating an endless loop of water. I have seen tight lots with retention grading for run off that creates pools of ejected water that will simply migrate back into the basement level.
You don't specify a CZ, but foam under the slab is better done now and it is a good value in many CZ not just 5 or 6. Particularly in a basement you wish to use.
The reason I am adamant about washed stone relates to the water table which will still be present in the interior of the foundation perimeter. I am not clear on why 18 additional inches of digging gets you to undisturbed soil for the footings or how that would relate to the water table. Whatever the case, the water table rise equally and the interior of the foundation will see the same conditions as outside the foundation walls. Hence the need to have more control over draining it than one sump location.
In my own somewhat odd circumstances, I have an intermittent water flow each spring which flows along the surface of the rock face my foundation is set on. The rock face is pitched so I was able to forego interior perimeter drain lines and simply connect the lowest point to the outside drain lines with a pass thru pipe in the footing. Obviously the hill continues and all lines drain to daylight. My under slab fill was scheduled for pit run plus 2" of washed stone. The pit run is basically dirt and random stone. Rather than hold the water for any period of time, I asked what the cost difference would be to go with entirely with washed stone. The difference was $4-500 in my case. All washed stone may actually save time and money.
Now all the water that comes up through the rock fissures is free to flow to the low point and out. If you were to consider the same option for a level foundation condition in a high water table, I would think you could establish better control over the water tables effects. A side advantage would be a convenient bed of stone to place radon mitigation pipes under the slab in advance of need, which I also took advantage of.
Last, but not least. The drain pipes must be set in washed stone beds that are protected with rated fabrics. I am a bit of belt and suspenders person, so I had full width pulls of fabric placed in the ground next to the footing/wall ahead of the fabric wrapped drain pipe placed next to the footing and then dropped washed stone over the pipe to cover by 2-3" and then folded the fabric over both directions to create a stone burrito. I don't plan on ever having the stone or the pipes silt out. A slick trick to place the stone was having it delivered in a cement truck with a boom conveyor. It made distribution and aiming very simple and quick.
All this may sound costly now, but the cost to remediate later are much, much worse.
I see Zephyr has added a very good point about sump pumps. Use nylon rope and add an eye bolt to the side of the sump wall. Especially if you are required to use a sealed type. The rope won't be of much use if it falls to the bottom when you pop the lid.
Thanks for the feedback. Sounds like leaving the weeper beside the footing is the way to go. Does anyone have a picture of what the potential sump pit will look like after I have poured the basement floor? Yes roger it was simply the wrong use of words. Will be using crushed stop surrounding the weeping tile outside the foundation as well as filling the inside, there is probably going to be close to 12 inches of it inside the house then the plan was foam insulation then the concrete floor. The discharge from the sump pump is not going to be issue as I have lots of room on the property and it will be drained well away from the house. You mentioned CZ, what does that stand for? And in my scenario I’m actually not digging a hole, just removing the organic and placing my footings there, will need to build up the grade significantly will clean fill after. Thanks again.
kesheshian,
It will be similar to this:
kesheshian,
CZ is just climate zone. Glad to hear you have room to pump away from the house. The area I moved from several years ago had lots of homes with endless loop sump pumps. Silly, but the battery backup sump people loved it.
If you have room to park the excavated organic layer on site, it may be a valuable resource to cover the fill you will be bringing in. As you do back fill, try to have the crew pack down the fill. If that is not practical, plan on waiting at least a full year of seasons - longer if spousal strife is not imminent by then. Soil settles longer than one might think and having a sidewalk or stair case go all tilty from rushing the landscaping can be a real pain.
Not to be a noodge, but plastic over the foam before the concrete. And have the first layer of stone compacted inside the foundation. Even if the soil inside the foundation is compacted first, the stone will set down into rather like nut topping on a frosted brownie. The additional depth of stone after the first is much less sensitive to compaction, though as I noted some would compact stone in lifts as well. I've seen it done on commercial and roadway work, but the engineering may be very different for those projects.