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WATER ENTRY IN BUILDINGS
AGE of MOLD, HOW OLD
BASEMENT CEILING VAPOR BARRIER
BASEMENT MOLD WATER IMPACT
BRICK WALL DRAINAGE WEEP HOLES
BUCKLED FOUNDATIONS due to INSULATION?
BUILDING DAMAGE ASSESSMENT & REPAIR
CONDENSATION on WINDOWS & SKYLIGHTS
DEW POINT TABLE - CONDENSATION POINT GUIDE
EFFLORESCENCE SALTS & WHITE DEPOSITS
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOD DAMAGED FOUNDATIONS
FLOOD VENTS & FLOOD PORTS
FLOODS in BUILDINGS, MOLD PREVENTION
FLOOR DAMAGE DIAGNOSIS
FOOTING & FOUNDATION DRAINS
FOUNDATION BULGE or LEAN MEASUREMENTS
FOUNDATION CRACKS & DAMAGE GUIDE
FREEZE-PROOF A BUILDING
FROST HEAVES, FOUNDATION, SLAB
HUMIDITY LEVEL TARGET
ROOF ICE DAM LEAKS
MOISTURE CONTROL in BUILDINGS
MOLD INFORMATION CENTER
NOISE / SOUND DIAGNOSIS & CURE
ODORS GASES SMELLS, DIAGNOSIS & CURE
SEWAGE BACKUP, WHAT TO DO
SEWAGE BACKUP TEST & CLEANUP
SEWAGE BACKUP PREVENTION
SEWAGE PUMP CLOG DAMAGE
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
SWEATING (CONDENSATION) on PIPES, TANKS
TOILETS, INSPECT, INSTALL, REPAIR
TRAPS on PLUMBING FIXTURES
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VENTILATION in BUILDINGS
WATER ENTRY in BUILDINGS
WINTERIZE A BUILDING
This article explains how sump pumps are used in buildings, describes the types of sump pumps, and describes how sump pumps should be installed, inspected, and maintained. We explain the difference between a sump pump, simplex and duplex sump pumps, a septic effluent pump, a sewage grinder pump, and an effluent pump.
This article explains the various types of pumps and their purchase, installation, inspection, and maintenance.
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Sump pumps, which we discuss on this page, are designed to remove unwanted water, such as surface or ground water that leak into a building. Sump pumps only have to pump water, never solids. Sump pumps are normally used to pump clear liquid, such as ground water from a wet basement sump pit or graywater from a basement laundry sink.
Our sump pump photo (left) is not a wonderful installation, but you can see the pump motor (red arrow), pump float switch (orange arrow), and flexible pump discharge pipe (white arrow) clearly. The water inlet in tihs case is at the bottom of the pump assembly (blue arrow).
Article Series Contents
Sump pumps are light-duty and unlike septic or sewage pumps, sump pumps have no ability to pass solid debris other than perhaps fine soil or silt that may be in groundwater. Some manufacturers may also call sump pumps de-watering pumps or submersible sump pumps. If you are confused between SUMP PUMPS used to remove ground water septic pumps (SEPTIC SYSTEM PUMPS) used to move sewage or septic effluent then also see SEPTIC SYSTEM PUMPS.
A sump pump is typically installed in a pit at the low end of a building's basement or crawl space floor or in another location where water needs to be removed such as in a boiler pit or an outdoor well pit. On occasion we find sump pumps installed outside of a building foundation to remove water from around the foundation of a poorly-sited (too low) building which has no natural drainage path to dispose of ground water by gravity.
In a bad building water entry situation water runs across the basement/crawl space floor into the sump pit where it is pumped away (after already wetting the building and inviting a mold contamination problem).
This condition pertains when water is entering a building through foundation walls, often because the roof drainage or surface runoff are directed right against the building foundation itself. Keeping gutters and leaders working and correcting outside drainage errors are critical in keeping water out of a building. Doesn't it make more sense to prevent water from coming into a building than to let it in and then pump it out?
In our flooding basement photo at above left, notice that there is a flood-line about half way up that oil storage tank? The little sump pump shown in the white bucket in the center of our photo is never going to handle such a huge volume of water. And even for modest water entry, the projection of that sump bucket lip above the floor level means water has to rise a few inches in this basement before it can even flow into the sump pit!
In a good situation, openings in the sides and bottom of the sump pit (photo at left) , or an under-floor drainage system direct subsurface water into the sump pit before the ground water level rises enough to send water into the building. Over several years of operation, and partly by pumping a little soil silt as it operates, a sump pump may actually improve the flow of under-floor water into the sump pit, thus reducing building water entry.
Septic pumps, sewage pumps, grinder pumps, and effluent pumps are not sump pumps, and they are discussed beginning at Sewage Ejector Pump Grinder Pump.
The distinction among these pump types is important. Choosing the wrong pump can mean a short operating life for the pump, an unreliable system, and unnecessary expense. There may be some confusion, depending on with whom you speak, because people don't always use just the right terms for construction or septic system parts - and the right sewage pump term, or right septic handling product versus the wrong one can be an important distinction.
Single submersible or pedestal sump pump: The photo on the left is what you're likely to see if your basement has a modern sump pump.
A pedestal type pump must keep its motor out of water and dry. Regardless of which type of pump we select, many installations require that only one single pump be installed.
We discuss the details of submersible and pedestal sump pump types below at Four Common Types of Sump Pumps.
Duplex sump pumps: The photo at left shows a duplexed sump pump system using pedestal type sump pumps. This was a really wet basement - a single sump pump simply could not keep up. In this installation .
When a building footprint or foundation layout is complex, or where the building is constructed over both basement space and one or more crawl spaces, it may be necessary to install multiple sump pumps to protect these various areas.
In a single large basement whose floor did not slope uniformly to a single low corner, it may be more economical to install two or even more sump pumps in problem areas than to tear up the entire basement floor to install a sub-slab drainage system.
Duplex sump pumps are illustrated and discussed further at Septic Pump Duplex System Designs.
Two Types of Duplex Sump Pump Installations: Alternating and Reserve
A simple installation provides a pump control float switch that turns on the backup pump only water in the pumping chamber reaches a level above that normally handled by the primary sump pump. This approach provides both pump backup and the ability to handle surges in building water entry loads on the sump pump system.
Alternating septic pump design: the two sump pumps are installed at the same location but are wired so that the pumps take turns, first one, and next cycle the other pump is turned on by the float switch.
This pump hookup is more common among septic pumping stations than among home sump pump de-watering systems, but it may be appropriate where a large volume of ground water has to be kept constantly out of a building.
An example we've seen was in the basement of a home on Long Island, NY in which the level of the basement slab was so low that flooding from Long Island sound would be nearly constant if the pumps failed.
The alternating sump pump approach has the advantage that both pumps are being exercised regularly, which reduces the chance of the ugly discovery that in the event you have to rely on a backup sump pump which has been sitting idle, waiting its chance to run, has in the interim, died.
Water & flooding alarm products are available in a variety of forms including battery-powered devices (we show one at Sewage Ejector Pump Grinder Pump) and even devices which can turn a light in a home or make a telephone call or inform an alarm company if a building is being subjected to flooding. Considering the very high cost of flood damage cleanup and mold remediation, we consider flood alarms a great idea for buildings which are often left unattended.
Sump pumps that have been added to an older structure often pump their discharge to the ground surface where it runs to a storm drain or area drainage setting.
If you have such a system be sure that the sump pump discharge empties where it meets these criteria:
Typically most of us just buy a 1/4 hp or 1/2 hp sump pump and throw it in the pit and see what happens. But you can guesstimate the rate at which water is flowing into the sump pit by knowing the sump pit dimensions and observing how long it takes the pit to fill to a measured depth. At Static Head of Water in the Well we give details of how to calculate the volume of liquid in a cylinder (if your sump pit is round) using pi (3.14) and the radius (1/2 the diameter of the cylinder) squared.
Volume cylinder = 3.14 x (water height in inches ) x (cylinder diameter in inches /2)2.
Example using an 18" diameter joint compound bucket as a sump pit, and assuming that it takes water 1 minutes to fill the pit to 1 inch..
Volume = 3.14 x (1 inch of water) x ( 18 / 2)2
Volume = 3.14 x 1 x 81 = 254 cubic inches of water rose in the sump pit in one minute
Water in-flow rate to the pit = 254 cubic inches per minute
Convert cubic inches to gallons as follows.
254 cu.in. / 1728 = .15 cubic feet.of water flowing into the sump pit per minute
.15 cu.ft. x 7.5 = 1.1 gallons of water flows into the pit per minute
This example let's us state a simple "rule of thumb" for joint-compund bucket-sized sump pits.
Choosing a De-Watering Sump Pump: Typical Pump Capacities in HP, Lift, & GPM Pumping Rate
Sump pumps for residential use range in horsepower from 1/4 HP to xx. Typical sizes are 1/3 HP and 1/2 HP. Prices (2012) run from about $100. to $200. for submersible pump models. Pedestal pumps and light duty sump pumps may sell for less than $100.
Sump pumps are rated for several important factors including horsepower and pumping capacity in gallons or liters per hour - a figure that varies by pump lift height. An individual sump pump's capacity will vary depending on the height to whch it has to lift its discharge water (higher lift means fewer gallons per hour) and other factors such as diameter and number of elbows in the discharge piping.
Watch out: be sure to consider both the anticipated de-watering flow rate you'll need and the pump's lift requirements. Typically if you are pumping out of a basement sump pit to ground level that's more than 5 ft. but less than 10 ft. of lift. But installations that have to lift higher distances and/or pump over longer distances and through multiple piping elbows need a more powerful pump.
Sump pumps on newly constructed buildings are often connected to the building foundation drain. We consider this a bad practice. It is a rare home more than 20 years old whose footing drains are intact.
If a footing drain discharge itself becomes clogged or damaged, sending the sump pump discharge into that system will not work: you'll simply flood another section of the building foundation, basement, or crawl space, or you may overload the existing foundation drain causing building water entry.
Connecting a sump pump to a municipal sewer drain is bad practice and illegal in some communities. You're adding to the municipal sewer plant's water overload during wet weather and you may thus be contributing to the discharge of raw sewage from the overloaded municipal treatment facility right into the environment.
Where permitted, we prefer to route a sump pump to a storm drain, or where soil conditions permit it might be discharged to a drywell.
De-Watering Sump pump inspection checklist
These simple sump pump dewatering trouble diagnostics may resolve pump capacity questions
If the sump pump motor is running or too frequently, constantly check the following:
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Frequently Asked Questions (FAQs) about Sump Pumps
Question: Does using a sump pump cause foundation undermining & increase of water movement towards the building?
This was the most informative article I've read during my extensive online research on the topic of "Basement Flooding" (see BASEMENT WATER ENTRY PREVENTION) . Ground water/high water table has been determined the cause of water entry into my basement "pit" area underneath my main sewer trap. We have a Basement Watch Dog Dual Sump Pump with battery backup installed however the constant presence of groundwater in our pit continues to worry us.
Our Staten Island, NY home location is situated where the properties behind, to the left and right of us are elevated. PVC fencing with sealed bottom moulding prevents rain water from cascading over the concrete/paver surfaces; however it is our belief that the groundwater underneath from all three directions have found a hydrostatic relief in OUR PIT! What recourse do we have? Any advice you can give us would greatly be appreciated. - Joe Apap 09/2011
Reply: increases in water flow towards sump pump, foundation undermine risk, possible solutions
Thanks for the nice note, Joe; we've been working hard on wet basement and wet crawl space information, particularly since recent hurricanes and tropical storms have led to so much flooding.
Increased water flow towards sump pump pit
Indeed sump pumps as basement de-watering systems work better over time precisely because the ultra fine soil particles pumped away open improved water drainage passages towards the sump pit. One of the first sump pump installations I worked on back in 1969 was installed to reduce the entry of water that used to squirt into a basement through its walls during heavy rains. When the sump pump was first installed it did not immediately stop the water entry, though it reduced it.
After just a few years the sump seemed to keep the water table below the basement slab and no more water squirted thorough the basement walls even in wet weather. Of course other conditions could have changed as well.
I have not been able to find data, and I doubt there is reliable data, about the "reach" of sump pump water movement past the building where it is installed.
Sump pumps might undermine a building foundation
I've read a few reports that in areas of fine soils a highly active sump pump may remove enough soil fines to actually cause foundation settlement or tipping. But it may just be urban legend - I've seen reports but no hard data.
Use an intercept drain system to reduce water movement towards and under a building, septic drainfield, or similar concerns
If it's cost justified you could consider a curtain drain around your property. Such a drain, a ditch to an adequate depth and filled with No4 crushed stone and perforated piping led to an outdoor pumping station could intercept water from neighbors and keep it away from your home. Your outdoor pumping station will need to be deep enough to be frost proof and it will need to discharge to an approved destination such as a local storm drain.
Also see BASEMENT De-Watering Systems.
Questions & answers or comments about how to choose, buy, install, & use sump pumps to keep water out of buildings
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