Sump Pump Problem 2

[bigmig]

I have a residential grade sump pump in my crawl space that has recently begun to run almost continuously due to the spring thaw. The house backs up against a hill that has expansive clay shale. We believe that the native water was traveling down the hill in the shale planes, and that the house excavation essentially severed the water path, so now the water ends up in our crawl space instead of traveling to regions unknown.

I pulled the sump pit cover and investigated the water source. It appears that all the water is coming through the bottom of the pit (i.e. high water table). Not a drip from the foundation drain pipes.

I am trying to head off a problem before it starts (i.e pump failure). So far I have looked at installing a larger pump and pit, but I feel like my pump is basically in a lake and all a big pump will do is pump more water. I will be investigating just turning the darn thing off and seeing if the hydrostatic head will balance, but then I get into another dilema with a moat sitting around my house after my house drain backs up.

The house is constructed on a grade beam/helical pier foundation system. I have been monitoring it via water level and the foundation is dead stable, but based on experience, having a lake around your house isn't exactly good.

Does anyone have suggestions about how I can solve the water problem? Has anyone seen this problem before? What solutions did you use? Or do I just live with a pump that runs every 6 minutes from February till June?

Thanks in advance.

 

[civilperson]

Dig around the perimeter of the base and install drain, (perforated pipe), and backfill with gravel wrapped in geofabric. Outlet the drain to daylight at level grade or connect to storm sewer. This should intercept the majority of flowing water and allow the sump to run less often.

 

[NinetyWt]

Two options I can think of are 1) a deep french train or 2) a deep cutoff wall.

Either way, you'd need to dig a trench on the upstream side of the house. I'd dig it at least two feet below the grade beam. Offset it outside of the zone of influence from the house foundation (ten to 20 feet maybe?).

For the drain, put a perforated pipe w/sock in the bottom and fill the rest with gravel. Either daylight the pipe on the other side of the lot, or connect it to some solid-wall pipe and then daylight it.

For the cutoff wall, dig a similar trench but fill it with slurry. The object is to 'turn' the water before it gets there.

You're going to have to make sure it extends far enough around the sides to keep water from 'end-running' the trench.

 

[bigmig]

Civil Person and NinetyWt,

Thanks for your responses. The foundation has a drain system (perforated pipe) with gravel and liner.

The funny thing is that I ran my pump to daylight and it was pumping so much that it covered the street (and my neighbors walkway) with algae. Forseeing the problem with having a permanent icerink in my neighbors driveway in winter, I re-piped the sump directly into my sewer line and now my neighbors like me more.

I thought about the cutoff wall, but would like to make sure I don't install an 8' deep wall when the water is at 9' down if you know what I mean. Also cutoff wall= tear out lawn, sprinkler, fence to get backhoe in, hire concrete sub....essentially big $$$. I'd rather just install another sump pit and pump for $150. Thanks for the suggestion though.

 

[Ron]

Dig your sump a bit deeper and larger, then use a pump with a separate float switch (the one you have likely has a built-on/in float switch, so it pumps when the water gets a few inches deep). Set the float switch to allow the pump to cycle a bit, that way it won't run continuously.

Failing that, do an interceptor drain cutting the subsurface flow plane and route around the house as others have noted.

 

[NinetyWt]

Quite so, either of my suggestion could get pricey.

I like Ron's suggestion of a deeper wet well with a higher 'trip' elevation.

I re-piped the sump directly into my sewer line

I hope you mean storm sewer as opposed to sanitary.

 

[bimr]

"I re-piped the sump directly into my sewer line "

That is a code violation almost everywhere.

Have you tried letting the water head rise and seeing if the flow stops at higher elevation?

The deeper the water level that you try to maintain will cause you to pump more water.

 

[dik]

Can you build a slight swale around the house to divert the water away from the home?

Dik

 

[bigmig]

dik,

The water is under the surface, traveling horizontally along shale layers that have been severed by my house excavation (see 1st post) so a berm on the surface wouldn't really help.

Regarding the code violation of piping storm water into a sewer line (!!), besides the obvious problem of sewer gas backing up and coming out your sump line, can someone elaborate on why the code won't let you do this, or in other words, what is the code trying to prevent. Sorry for the elementary question, storm and sewer is beyond my field of experience.


Bimr, I thought about letting the water rise until it stops, but the problem is that it will stop (best case) at the top of the sump pit, which is equal with my crawl space grade. This is the same as backing up my drainage system, which could lead to a variety of moisture problems including humid (mold) crawlspace, ice pressures next to foundation, expansion of the clay soils I'm built in etc.

Ron, your suggestion is the best one so far, thanks for your suggestion.

 

[semo]

Code does not allow you to do this as the City isn't in the business to treat stormwater or groundwater at their wastewater treatment plant. This is called I/I (inflow/infiltration) and during storms can potentially overload the wastewater treatment plant with water that doesn't need treating.

It is the same principal as piping your roof drains into the sewer system.

I think Bimr is mentioning a modification to Ron's proposal. Turn off the pump and see where it rises to. Then you can set the existing pump at a higher elevation. Why add a second pump? Then you will have two pumps running. Put a block under the existing pump and depending on the inflow rate, it will probably start cycling as you aren't trying to keep the water level as low.

 

[NinetyWt]

Code does not allow you to do this as the City isn't in the business to treat stormwater or groundwater at their wastewater treatment plant. This is called I/I (inflow/infiltration) and during storms can potentially overload the wastewater treatment plant with water that doesn't need treating.

It is the same principal as piping your roof drains into the sewer system.

To expound on this, the municipality typically charges you for sanitary service. A simple way for them to do this is to charge you for the same amount of drinking water you used. You may notice this charge on your water bill.

If you are adding stormwater or groundwater to their system, they have no way of charging you for that sewer use. For that reason, this is often termed an illicit connection.

Some places will allow connections to the stormwater drainage system, but one should always check before making such a connection.

 

[NinetyWt]

I forgot to mention the capacity issue, which is what semo noted above.

The wastewater system's capacity is based on the predicted amount of graywater produced by the development. In other words, there is a certain amount of graywater which your home is expected to produce. If you add extra water to that system, it can overload or overwhelm the system. This is another reason to prohibit illicit connections.

 

[concretemasonry]

Now that the connection to the sanitary sewer line has been explained correctly, the question is back to the amount of pumping being done.

Sump pumps are made for near continuous operation when required.

The first question is - Do you have a check valve immediately above the pump to eliminate the short cycling that occurs when the line tries to drain or siphon backwards?

It is obvious that your drain tile system is working properly. Make sure you have a high quality pump and set the limits to the maximum height of water you want to keep in the sump pit. There is nothing wrong with a pump that runs nearly continuously for a predictable small portion of the year. A cheap back-up pump on the shelf is always good insurance.

Depending on the geography, the discharge should be to daylight well away from the home and drain away. Depending on your climate, there are pop-up valves that permit buried lines across a yard. If you have a gutter or storm water ditch near a road, you can pump underground and discharge there. If you discharge into a gutter, a check valve may be required to prevent a backflow if the gutter flow from a short storm is greater than the capacity. A permit to cut into the curb may be required. Usually, getting permission is easy since you are not adding and sewerage to the discharge.

Dick

 

[bigmig]

concretemasonry,

Yes there is a check valve. The climate is mountain (i.e. Colorado) so freezing is a concern. There isn't any storm water ditch or storm gutter. Each houses' drainage output just flows into the curb on the street surface. The developer graded the surface around each house to drainage swales that lead to the street. The swales are not lined, just bare dirt, or clay shale in my case. The nearest storm water ditch (about 50' across) is about 3/4 of a mile from the site and I believe is what is known as a "100 year ditch".

Your suggestion about having a backup pump with water alarm is the route I'm going to take. I am investigating recycling the ground water for irrigation purposes (summer only).

 

[civilman72]

I see this issue in Colorado all the time, but often the cause and solution are not easy to identify. Especially with expansive clay shale, you never really know how/where the water will "appear."

"The foundation has a drain system (perforated pipe) with gravel and liner."

With the issues you have described, this is the first thing that you should investigate. A clogged french drain could be the main reason you are having these issues. Some questions:

Can you find the daylight/outlet of this drain? If you can, is there any water flow? If you have water in your crawl space, but no flow at the outlet of your french drain - this almost always indicates a clogged french drain. If you are seeing increased pumping over time (i.e. a few years), this could also be an indication that your french drain is slowly clogging over time. Was there any recent construction adjacent to the house that could have resulted in a damaged french drain?

If you can't find your outlet point, than more than likely your french drain is collecting some of the groundwater, but without an outlet, it's not doing you any good in decreasing the amount of water in your crawl space.

If you have answers to these questions, I may be able to help some more...but as stated before, finding the cause of a wet crawl space can often be a struggle.

 

[chicopee]

How effective would an underground overflow pipe near the top of the sump be?

 

[kslee1000]

I would listen to civilman72 on this case. Your description:

"I pulled the sump pit cover and investigated the water source. It appears that all the water is coming through the bottom of the pit (i.e. high water table). Not a drip from the foundation drain pipes."

indicates there is something wrong with your drain system. Dick's suggestion (spare pump) is absolutely necessary.

 

[pfp1334]

I am in the process of installing/replacing crawlspace drains and sump pumps for several units in a townhome complex. Can anyone clarify for me what permitting requirements there are if any in the State of Colorado with respect to daylighting of the water?

What restrictions may there be regarding discharge around streams?

 

[bigmig]

pfp1334,

Call the governing building department, as I'm sure that the requirements depend on which county, type of ground water, and things that could be affected on the surface by you pumping water onto them. They would also be able to direct you to the specific requirements regarding discharge around streams.

 

[csd72]

When i have done drainage I have always specified two pumps for this reason. If one fails you have a backup until it can get replaced.

It is easy to say that you can hire a backup, but what happens if the residents are away for a few weeks when the pump fails?