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Question DetailsAsked on 8/29/2017

what is the difference between a septic tank and septic pump tank?

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2 Answers

0
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Hello Septrus,


Thank you for reaching out. I found the following link that gives a good explaination of different septic systems. http://www.kingcounty.gov/depts/health/environmental-health/piping/onsite-sewag
e-systems/maintenance/how-OSS-works.aspx


We are happy to help you with finding a provider as well! If you have not done so already, please go to www.angieslist.com to set up a membership. Once completed you will have access to highly rated service providers in your area. By searching the “Wells and Pumps” category, you will find top rated providers that can fit your needs.

Best,

Iann M

Answered 1 year ago by Member Services

0
Votes

Iann gave you an excellent article link on types of tanks - but your Search the List category would be Septic Tank, not Well and Pump as he said - that category is for waster wells, very few of that type contractor gets involved in septic systems. However, in most areas the actual design (and soil testing to design the leach field) has to be done by a licensed/registered Civil Engineer (no Angies List Search the List category for that), who generally also has to certify to the actual construction.


Don't know how much you know about how septic systems work - here is a primer FYI if needed:


http://buildingadvisor.com/buying-lan...


A Septic tank is any tank which holds the sewage and (using fixed high and low level baffles inside the tank usually) removes most of the floatables, grease, and solids before the effluent goes to the leach field to soak into the ground. A "gravity septic tank" is the usual type - where the sewage flows from house to tank by gravity flow in the sewer line, then the effluent (the water separated out from the sewage) flows by gravity to the leach field, and the tank is not generally designed for the top to go underwater, or for the tank to back up and potentially overflow.


Where gravity flow is not possible, there are several variations:


1) if the house is located in a low spot or due to drainage conditions has to be lower than the leach field (which typically has to be 3 to 6 feet above highest seasonal groundwater to the bottom of the pipes, depending on soil permeability), or if the basement piping is not a bit higher than the septic tank inlet pipe, then the house may have a sewage grinder lift pump, which grinds and pumps the household sewage to the septic tank on demand. A sewage lift pump may serve only the lowest part of a house (commonly a basement bathroom or in-law apartment for instance), but in some cases all drain water/sewage from the house has to be pumped up to the septic tank if the house is in the lower part of the property, or commonly if along/near a drainage or stream so the tank and leach field had to be put further away to get on high enough ground to be the legal elevation above seasonal groundwater or flooding levels.


In many such low-level or floodplain houses, the sewage grinder lift pump from the house then feeds to a conventional gravity-flow septic tank and leach field system, in others one of the other following options is necessary.


2) sometimes the septic tank can be put near the house and get gravity flow to it from the house (generally much more desireable than having a sewage grinder pump), but due to lot layout/elevations, groundwater levels, required distances between leach field and property lines, houses, other septic systems, water wells, or bodies of water, the leach field has to be put at a higher elevation or a significant distance from the tank so gravity flow will not work, then you need an effluent lift pump to pump the tank outflow to the leach field. This can be a pump in a separate pump pit or wetwell near the tank outlet (my preference if feasible), or can be a pump inside the septic tank (generally messier to work on for maintenance/repair and commonly more prone to clogging, so I prefer to avoid if possible).


A "Septic Pump Tank" has the effluent pump built into the tank, and is generally required by law (though not always) that the tank access hatches are gasketed and bolted so water can not get in or out of it other than through the piping and so it cannot overflow if the pump fails. Some tanks with pumps built in are just normal gravity tanks with an added pump well near the outlet end. Sealed access hatch tanks are commonly used in areas where it is required by law - usually in areas where the groundwater or surface flooding may come above tank effluent exit level.


The effluent pump, regardless of location, has high and low limit on/off float switches and in most areas also has to have (and always should have even if not required) power loss and overfill alarms. The pump kicks on when the liquid level in the tank reaches a certain level (about the normal outlet pipe level if that were in use), and pumps until the level in the tank drops to the design level (typically a few feet), when the low-limit switch turns the pump off - same way a basement sump pump works. It is also highly desireable to have an alarm light and alarm - at least a light and audible alarm, and indoor alarm, auto-notification WiFi and landline/Cellular autodialer and alarm company autodialer alarms are also available. That way if the system fails (due to pump failure or power failure) and the liquid level reaches the alarm float switch the visible/audible alarm sounds (and autodials if so equipped). This system should have battery backup in case of power failure, because in that case the effluent pump will also fail.


It is possible to have battery backup on the pump and alarms - but generally because of the pump horsepower battery backup does not last long, and the battery generally needs to be installed indoors in cold areas or have a heater in the pump well or a well-insulated pump well so the sewage heat keeps it warm enough to it does not lose power due to the cold. Anytime you have an effluent or sewage lift pump you quickly get into a situation of what-if's - what you should alarm for, and backups for alarm and maybe pump power, sometimes backup parallel pump even - some people go bare minimum and count on smelling sewage overflowing as their alarm, some go with duplicative systems and large battery backup systems and several forms of alarming.


Of course, what will happen in the event of a failure can heavily inflluence the amount of care needed - if an overflowing tank will flow downhill right into your house the situaiton is a bit different than if it will flow into a farm dungheap.


One other thought on septic system design - consider what will happen if you get massive rains (think current Texas flooding) which cause surface flooding or elevated groundwater which can flow into the tank (or cause it to overflow), or casue the leach field to fill up. You want to try to avoid a situation where it can backflow into the house - and note that backflow check valves in septic system generally do not close fully. It is always desireable to make it so there are air gaps in the system if it could back up into the house - places where the incoming fluid to the tank and/or top the leach field (as applicable) come in through an elevated pipe (above ground/high water level) with airgap so backflow can not come back through the piping to the house and overflow the house drains. With sewage lift / effluent pumps this is easily done, and is commonly tied into the household sewer line vent line for venting and to provide the airgap. I have seen cases where a household sewage lift pump elevated the fluid as much as 15-20 feet above the pump to ensure this backflow cannot occur.


An outdoor effluent lift pump of course only has to get above ground level unless required to be higher by code or if overflow at that point will rapidly make it to the hosue - but generally if it is going to overflow a foot or two stickup airgap at the tank then the leach field will be bleeding effluent to the surface anyway. [BTW - you do need to be aware of the odor issue from vent pipes - that sometimes mandates moving the septic tank or at leat the vent pipe further away from the house, or tying it into the household vent stack.]


Don't know how much you know about how septic systems work - here is a primer FYI if needed:


http://buildingadvisor.com/buying-lan...


A Septic tank is any tank which holds the sewage and (using fixed high and low level baffles inside the tank usually) removes most of the floatables, grease, and solids before the effluent goes to the leach field to soak into the ground. A "gravity septic tank" is the usual type - where the sewage flows from house to tank by gravity flow in the sewer line, then the effluent (the water separated out from the sewage) flows by gravity to the leach field, and the tank is not generally designed for the top to go underwater, or for the tank to back up and potentially overflow.


Where gravity flow is not possible, there are several variations:


1) if the house is located in a low spot or due to drainage conditions has to be lower than the leach field (which typically has to be 3 to 6 feet above highest seasonal groundwater to the bottom of the pipes, depending on soil permeability), or if the basement piping is not a bit higher than the septic tank inlet pipe, then the house may have a sewage grinder lift pump, which grinds and pumps the household sewage to the septic tank on demand. A sewage lift pump may serve only the lowest part of a house (commonly a basement bathroom or in-law apartment for instance), but in some cases all drain water/sewage from the house has to be pumped up to the septic tank if the house is in the lower part of the property, or commonly if along/near a drainage or stream so the tank and leach field had to be put further away to get on high enough ground to be the legal elevation above seasonal groundwater or flooding levels.


In many such low-level or floodplain houses, the sewage grinder lift pump from the house then feeds to a conventional gravity-flow septic tank and leach field system, in others one of the other following options is necessary.


2) sometimes the septic tank can be put near the house and get gravity flow to it from the house (generally much more desireable than having a sewage grinder pump), but due to lot layout/elevations, groundwater levels, required distances between leach field and property lines, houses, other septic systems, water wells, or bodies of water, the leach field has to be put at a higher elevation or a significant distance from the tank so gravity flow will not work, then you need an effluent lift pump to pump the tank outflow to the leach field. This can be a pump in a separate pump pit or wetwell near the tank outlet (my preference if feasible), or can be a pump inside the septic tank (generally messier to work on for maintenance/repair and commonly more prone to clogging, so I prefer to avoid if possible).


A "Septic Pump Tank" has the effluent pump built into the tank, and is generally required by law (though not always) that the tank access hatches are gasketed and bolted so water can not get in or out of it other than through the piping and so it cannot overflow if the pump fails. Some tanks with pumps built in are just normal gravity tanks with an added pump well near the outlet end. Sealed access hatch tanks are commonly used in areas where it is required by law - usually in areas where the groundwater or surface flooding may come above tank effluent exit level.


The effluent pump, regardless of location, has high and low limit on/off float switches and in most areas also has to have (and always should have even if not required) power loss and overfill alarms. The pump kicks on when the liquid level in the tank reaches a certain level (about the normal outlet pipe level if that were in use), and pumps until the level in the tank drops to the design level (typically a few feet), when the low-limit switch turns the pump off - same way a basement sump pump works. It is also highly desireable to have an alarm light and alarm - at least a light and audible alarm, and indoor alarm, auto-notification WiFi and landline/Cellular autodialer and alarm company autodialer alarms are also available. That way if the system fails (due to pump failure or power failure) and the liquid level reaches the alarm float switch the visible/audible alarm sounds (and autodials if so equipped). This system should have battery backup in case of power failure, because in that case the effluent pump will also fail.


It is possible to have battery backup on the pump and alarms - but generally because of the pump horsepower battery backup does not last long, and the battery generally needs to be installed indoors in cold areas or have a heater in the pump well or a well-insulated pump well so the sewage heat keeps it warm enough to it does not lose power due to the cold. Anytime you have an effluent or sewage lift pump you quickly get into a situation of what-if's - what you should alarm for, and backups for alarm and maybe pump power, sometimes backup parallel pump even - some people go bare minimum and count on smelling sewage overflowing as their alarm, some go with duplicative systems and large battery backup systems and several forms of alarming.


Of course, what will happen in the event of a failure can heavily inflluence the amount of care needed - if an overflowing tank will flow downhill right into your house the situaiton is a bit different than if it will flow into a farm dungheap.


One other thought on septic system design - consider what will happen if you get massive rains (think current Texas flooding) which cause surface flooding or elevated groundwater which can flow into the tank (or cause it to overflow), or casue the leach field to fill up. You want to try to avoid a situation where it can backflow into the house - and note that backflow check valves in septic system generally do not close fully. It is always desireable to make it so there are air gaps in the system if it could back up into the house - places where the incoming fluid to the tank and/or top the leach field (as applicable) come in through an elevated pipe (above ground/high water level) with airgap so backflow can not come back through the piping to the house and overflow the house drains. With sewage lift / effluent pumps this is easily done, and is commonly tied into the household sewer line vent line for venting and to provide the airgap. I have seen cases where a household sewage lift pump elevated the fluid as much as 15-20 feet above the pump to ensure this backflow cannot occur.


An outdoor effluent lift pump of course only has to get above ground level unless required to be higher by code or if overflow at that point will rapidly make it to the hosue - but generally if it is going to overflow a foot or two stickup airgap at the tank then the leach field will be bleeding effluent to the surface anyway. [BTW - you do need to be aware of the odor issue from vent pipes - that sometimes mandates moving the septic tank or at leat the vent pipe further away from the house, or tying it into the household vent stack.]

Answered 1 year ago by LCD




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