Your Sump Pump: The Workhorse for Basement Leak & Basment Drainage Systems

Your home, if it was built in the last 50 years, would have been built with some sort of drain The PERMA-PUMP Systemat the bottom of the foundation wall on the outside that runs around the entire outside perimeter. This drain, depending on when and where your home is built, would likely tie into a municipal combined or storm sewer system. In a previous blog article, Basement Drainage & Basement Flooding, we outline the different types of municipal sewer systems and how your home’s perimeter drain relies on those drains to function properly. When perimeter drains fail, many homeowners will have a sump pump installed to help keep groundwater from entering the basement.

Sump pumps are the backbone of many waterproofing or groundwater management systems and are most often installed in maintenance or repair situations. They mechanically lift groundwater from beneath your foundation and send it to a storm drain, ditch, dry well or some other area.

Nowadays, many municipalities across Canada mandate that sumps pumps be installed in newly constructed homes. Rather than discharge the newly installed perimeter drain into the municipal storm sewer, municipalities such as Charlottetown, PE and Barrie, ON mandate that the perimeter drain be discharged to a sump pump which then pumps the water to the surface of the yard or a dry well to either soak into the ground or run off. Municipalities promote this as a green initiative in order to conserve water, however, it also comes down to cost. Municipalities are mandated to treat (or at least filter) stormwater before it is discharged into our lakes, rivers and oceans. Stormwater treatment costs money. Adding clean groundwater to the system reduces the storm sewer capacity and increases treatment costs.

There are two main types of sump pumps; submersible and pedestal. Pedestal pumps have an air-cooled electric motor that sits at the top of a pedestal at the bottom of which is the pump. Pedestal pumps typically are more energy efficient and are relatively inexpensive. Submersible pumps sit in the sump basin and use the surrounding water to cool the motor. Submersible pumps typically cost more money and use more electricity, but also usually have larger capacities and are often more reliable. Pedestal pumps are all but going extinct due to changes in the National Building Code of Canada 2010 noted below. The Code mandate that sump pumps have:

2) Covers for sump pits shall be designed

a) to resist removal by children, and

b) to be airtight in accordance with Sentence 9.25.3.3(7).

These regulations practically prohibit the use of pedestal pumps because they cannot be easily or practically installed to meet the requirements above.

Your pump should be large enough to evacuate water from the sump faster than it enters the sump basin and strong enough to push the water to where it has to go, usually referred to as head. Dynamic Head is equal to Static Head (vertical lift) plus Friction Head (friction of the water passing through the pipe).

The sump basin, the hole in which the pump is set, plays a crucial role in the overall dewatering system. A properly sized pump and sump are crucial for best performance of your system. The basin should be large enough to meet Code requirements and be large enough to accommodate the volume to accommodate the pump capacity plus a reserve. Water level in the sump basin should never be allowed to raise higher than the bottom of the inlet pipe. An 18in diameter (smaller area than the new code requires) sump basin holds 1 gallon of water per inch. The typical stroke or draw down of a pump cycle is only 5-7 inches. This means that your only pumping a maximum of 7 gallons of water per cycle. This means your pump will frequently cycle on and off. Increasing the sump basin diameter to 24in (exceeds code requirements) doubles the volume of water per inch, thus, cutting the number of pump cycles in half, extending the life of your pump. Not to mention that it will be less noticeable.

I have seen many contractors and homeowners alike beat a hole in the basement floor, dig a small hole and throw a pump in the hole. I have also seen countless pumps installed in 5 gallon pails and milk crates in these sub-floor holes. You don’t want to do (or allow a contractor either) to do either because:

  1. They don’t meet the requirements outlined in the National Building Code of Canada 2010 Volume 2 Division B Paragraph 9.14.5.2.

  2. They can and will allow large diameter solids to enter the sump. These solids are usually rocks and can easily jam the pump.

  3. There is no practical way to provide them with a sealed, secured lid to meet Code requirements.

  4. They are small and will allow your pump to cycle on and off frequently.

Sump basins should be rigid enough to prohibit the side walls from caving in due to lateral soil pressure. The sides of sump basins should be perforated to allow water ingress and prevent the basin from floating. Keep in mind the diameter of the perforations need to be smaller than the diameter of the largest solids the pump is rated to evacuate! And of course, the lid needs to be sealed and either bolted or screwed on to prevent children from opening it. This also helps to keep debris and other foreign matter out of the basin.

The pump switch is responsible for automatically turning the pump on and off. There are many different types of switches available for sump pumps from mechanical float switches to tethered switches to diaphragm switches and electronic switches. Regardless of how they do the task, they all serve the same purpose; when the water level raises to a pre-determined level, the pump turns on; and, when the water level falls, turn the pump off. The pump should have a switch that is adjusted to allow the pump to evacuate at least 45-60 litres (12-15 gallons) of water at a time (providing an adequately sized basin) in order to minimize cycling and premature wear caused by a high cycle frequency.

The vertical or mechanical float switch is a float attached to a pole. The float travels vertically  inside the sump pit, restricted to basic up and down movements, and when it moves, it triggers the necessary action for engaging or disengaging the pump.

A tethered float switch is as the name implies, a float that is tethered to the pump and floats on the water in the sump pit. The tether moves up and down with the water and turns the pump on and off according to predetermined water levels. Float switches operate mechanically and depend on the adjustment of the float for proper function. While these are easy to maintain with simple operation, there are a number of problems that can cause a malfunction. The main problem that could cause your pump to work incorrectly is obstruction, usually from getting tangled or hung up on pipes and other devices in the basin and due to debris ending up in the sump pit.

Diaphragm switches use water pressure to turn the pump on and off. As water level rises, so does the water pressure which pushes against a rubber diaphragm which then pushes on a spring loaded switch which turns the pump on. When the water level falls, the spring pushes the rubber diaphram out, disengaging the switch, and thus, turning the pump off. Diagram switches are subject to failure of the rubber diaphragm due to tears caused by debris and sometimes the spring.

Electronic switches are the least common and are the most expensive. These switches have sensors which are placed inside the basin and “feel” when water levels get high or low and turn the pump on or off. Electronic switches are very reliable and don’t get hung up in the basin.

A good pump system will also include a high water alarm that will send an audible signal when water levels in the basin get too high. The alarm should be set to give enough time to check the pump switch, fuse panel, circuit breaker or call for help. Some high water alarms can be wired into a home’s alarm system or home automation system. High water alarms are worth the minimal expense.

It is a good idea to protect your home with a back-up pump. Sump pumps of course, are a mechanical devices that run on electricity. A quality sump pump should last at least ten years but are still prone to power outages and mechanical failures. Most often, when you need your pump, it is in stormy, windy, rainy conditions which are also likely to cause a power outage, thus, rendering your traditional sump pump useless. Even if you have a back-up generator that you turn on manually, you may not be home to turn it on. Is that a risk you want to take? Besides, who wants to worry and be stuck home every time bad weather is forecast? Even good quality pumps can fail from time to time due to mechanical issues such as faulty switches, stuck, tangled or dirty floats, blown circuits, worn motors, etc. Back-up pumps such as battery powered pumps are 12volt pumps that often run at 1/2-3/4 of the capacity of most sump pumps and offer great protection; something every pump system should come standard with!

One of the other biggest questions when designing a sump pump system is where to discharge the water? How far away from the house? Above or below ground? Since most municipalities won’t allow you to discharge a sump pump into the sewer system and often, when allowed, it is impractical. So what do you do? The answer is to route the discharge pipe through the foundation wall (the space between the concrete and pipe will have to be sealed later), run underground to either daylight at a ditch or over a bank into a dry well at least 5 meters (15ft) from the foundation.

When running to a ditch or dry well, it is advisable to ensure that both a backwater (check) valve and a grate are installed. The backwater valve will prevent water from backing up into your sump basin while the grate will prohibit rodents and debris from getting in the discharge pipe.

One has to be certain that normal high water level in the discharge area is not as high or higher than the discharge point of the pump. In fact, Paragraph 9.14.6.1 of the National Building Code requires the bottom of the drywell be higher than the natural groundwater level. Running the discharge pipe underground will not only protect it from freezing, as will running the pipe at a 2% slope, but it will keep the pipe out of the way such as in the summer when cutting grass, etc.

A dry well can be filled with 25mm (1in) washed stone or have a larger pre-manufactured sump basin installed to minimize sediment and prevent sidewall collapse. The top of the dry well should be flush with the surrounding grade so that in the even the well gets filled, water can spill out onto the surrounding ground. Of course, this means that geotextile (filter fabric) needs to be installed at the top with a 150mm (6in) layer of washed stone above it to prevent grass clippings, leaves and other debris from getting into the dry well.

In urban settings where water use is metered and regulated, it is a good idea to install a large below-ground tank to not only discharge a sump pump, but downspouts as well. Rather than allowing this water to dissipate into the surrounding ground as with a dry well, water is held in the tank for use in gardens and gardens and to wash cars.

The National Building Code of Canada 2010 Volume 2 Division B

9.14.5.1 Drainage Disposal

1) Foundation drains shall drain into a sewer, drainage ditch or dry well.

9.14.5.2 Sump Pits

1) Where a sump pit is provided it shall be

a) not less than 750mm deep,

b) not less than 0.25m² in diameter

c) provided with a cover.

2) Covers for sump pits shall be designed

a) to resist removal by children, and

b) to be airtight in accordance with Sentence 9.25.3.3(7).

3) Where gravity drainage is not practical, an automatic sump pump shall be provided to discharge the water from the sump pit described in Sentence (1) into a sewer, drainage ditch or dry well.

9.14.5.3 Dry Wells

1) Dry wells may be used only when located in areas where the natural groundwater level is below the bottom of the dry well.

2) Dry wells shall be not less than 5m from the building foundation and located so that drainage is away from the building.

Supplemental reading: Site Grading and Drainage to Achieve High-Performance Basements by M.C. Swinton and T.J. Kesik for the National Research Council.

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