Septic System Question

RituallyPure · 06-13-2003, 10:39 PM

I have a septic setup where I have a standard septic tank where all of the solids go, and the liquids are pumped out to the town's sewer system.

My question is this... What would make a septic pump run for extended periods of time?

Normally, assuming something is being added to the system- the pump will run every half hour or so for about 5 minutes. At night maybe once every 2 or 3 hours. But lately, it's been running basically non-stop. Every 5 to 10 minutes, it comes on for 5 - 10 minutes, and this is during the day. At night (3am), it basically does the same thing. Every 10 minutes it runs for about 5 or 10 minutes, then shuts off.

What would cause it to do this?

Thx in advance for any help.

R.P.

M_Six · 06-13-2003, 10:59 PM

If it's been raining a lot you could have groundwater infiltration. The groundwater seeps into your tank, fills it up, and trips the pump float.

thekingofpain · 06-14-2003, 12:36 AM

Or the switch/float/pump is funky...

Gomer · 06-14-2003, 10:16 AM

My guess is that your pump is within a pump vault in the tank. Water flows through a filter into the vault, the pump pumps the water out of the vault. The pump floats are also within this vault as well.

Now if this filter starts to clog up, the pump will come on and pump water out of the vault faster than the water can flow through the filter and replenish the volume of the vault. So the pump empties the vault and the pump shuts off. However, the water level in the tank is still too high and it refills the pump vault.

Ground water infilitration is a possibility as well, but I think the scenario above is more likely. How old is the system? Has there been any maintenance? You probably could find a company nearby to clean and inspect it on a yearly basis for $150-$250 or so. The first time you have to pull the lid and clean one of these filters you will see it is worth it.

If you want to try to clean it yourself, get some heavy, long rubber gloves, pull the filter up out of the vault, and use a pressure washer to spray it down, with all the wash water going back into the tank. If you don't get it taken care of soon, you may wind up with a backup. If not you will certainly shorten the life of the pump.

FYI, I design these sorts of systems day in and day out.

alivin · 06-14-2003, 09:51 PM

It could be that your check valve is faulty or needs cleaning. If it is not working all the liquid in the pipe is running back into the tank and then it has to start all over again.

jnas · 06-14-2003, 11:09 PM

Check your toilet and make sure it is not running constantly. This would make the pump operate more often than normal.

Good luck

John

RituallyPure · 06-15-2003, 12:12 AM

Update;

Had a friend come out and diagnose it today.. He said faulty check valve, so I'm going to have someone come out and fix it this week... Most certainly isn't anything I'm interested in dealing with!

He explained it to me, but I still don't really understand what the problem entails. The pump is in the basement of the house, the septic tank is outside (solids) and the town has a sewer system that takes liquids.

He said that basically, the pump finishes its job - and then the rest of the street's water basically fills up our system, so our pump is basically pumping for the whole street... But I don't get how that works... :S

My friend initially suggested that I unhook the pump myself and take it in, but as long as there's no pump - there's no toilet flushing, no showers, no laundry, etc... so I figure if I have someone come out with the necessary parts, they can fix it here, and it'll be done faster.

My main concern here is pump failure, or WORSE - sewage backup into my newly finished and furnished basement. I asked whether backup was a risk - but he never really did clear that up. Does anyone know if it is?

R.P.

Gomer · 06-15-2003, 01:01 AM

There are two sorts of collection systems for communities that utilize septic tanks as part of the process. STEP Sewer and STEG Sewer systems. STEP (septic tank effluent pump) sewer is the system I assumed you had. STEG (septic tank effluent gravity) sewer is the system it sounds like you have.

The pump in your basement is probably what is known as an ejector pump. It has a small basin that collects all waste (solids and all) from the house and pumps it out to the septic tank. Most houses will simply have this waste flow by gravity out to the septic tank. Houses where there is wastewater that is below the water level in the tank (ie finished basements) need to use a pump to get the water into the septic tank.

Now as I said before, there are two types of sewer collection systems that use septic tanks, STEP and STEG. In a STEP system there is a seperate pump within the septic tank that pumps water (no solids) into a common force main that is under pressure. So each house has a pump hooked to the same pipe basically. If a check valve fails in this sort of system it is not a good thing as the neighbors pump (inside his septic tank) will pump all the liquid into your septic tank. Multiply this times several neighbors and it gets ugly in a hurry.

In a STEG system... The wastewater gets into the septic tank either via gravity, or via an ejector pump (as in your situation). Once the waste is in the tank the septic tank acts just as it would if you had a normal drainfield. Except instead of flowing into a drainfield via gravity, it flows into a collection sewer (this sewer is a small diameter pipe (2-3"), much smaller than standard sewers which handle solids).

If you don't have a pump in the septic tank itself you have a STEG system. The bad check valve in the ejector pump causes the water in the pipe to drain back into the pump basin after each cycle. There should be no water from the septic tank flowing back. So there really isn't great concern that sewage backupwill occur.

Quote:

He said that basically, the pump finishes its job - and then the rest of the street's water basically fills up our system, so our pump is basically pumping for the whole street... But I don't get how that works... :S

My friend initially suggested that I unhook the pump myself and take it in, but as long as there's no pump - there's no toilet flushing, no showers, no laundry, etc... so I figure if I have someone come out with the necessary parts, they can fix it here, and it'll be done faster.

That part confuses me as well. It shouldn't happen that way. That pump in your basement only moves the water into the septic tank. Once it gets there one of two things happens... either another pump pumps it somewhere else... or gravity (the water justs flows downhill) takes the water via the sewer downgrade to where-ever it goes.

Imagine if what he said was the case... and you removed the pump and the check valve, all the neighbors water would flow backwards through your septic tank and fill your basement. I don't see how it can happen that way. Groundwater maybe, but not others wastewater. Do you have a high water table there? Has it rained alot? Water leaking into the tank and back into the house through a faulty check valve is the only thing that would cause it to act like you described.

Am I correct in assuming you have a STEG not a STEP system? You do not have a pump in the septic tank as well... correct?

edited for some typo's =) (late post)

RituallyPure · 06-15-2003, 06:06 PM

Quote:

There are two sorts of collection systems for communities that utilize septic tanks as part of the process. STEP Sewer and STEG Sewer systems. STEP (septic tank effluent pump) sewer is the system I assumed you had. STEG (septic tank effluent gravity) sewer is the system it sounds like you have.

I would assume so, the town refers to it as a "gravity system". We also have what is referred to as a "sewage lift station"

here in town, as well.

Quote:

If you don't have a pump in the septic tank itself you have a STEG system. The bad check valve in the ejector pump causes the water in the pipe to drain back into the pump basin after each cycle. Say you have 30 gallons of drawdown in your basin and There is should be no water from the septic tank flowing back. So there really isn't great concern that sewage backupwill occur.

I would guess that this is the case (water draining back through the pipe into the basin). In this town's system, there are no pumps in the septic tanks.

Quote:

That part confuses me as well. It shouldn't happen that way. That pump in your basement only moves the water into the septic tank. Once it gets there one of two things happens... either another pump pump's it somewhere else... or gravity (the water justs flows downhill) takes the water via the sewer downgrade to where-ever it goes.

Maybe he was confused.. You seem to be a little more knowledgable on this stuff than he was. lol..

Quote:

Imagine if what he said was the case... and you removed the pump and the check valve, all the neighbors water would flow backwards through your septic tank and fill your basement. I don't see how it can happen that way. Groundwater maybe, but not others wastewater. Do you have a high water table there? Has it rained alot? Water leaking into the tank and back into the house through a faulty check valve is the only thing that would cause it to act like you described.

The water table here is relatively high, but it's never been known to interfere with the sewer system. Hasn't really rained in a while, either.

Also - this basin you've described as being in the house, which collects water before the pump pumps it out to the septic tank - would this commonly be sealed under the basement floor?

The town is going to be upgrading everyone to a completely central sewer system this summer (no more septic tanks, pumps), due to deteroriating systems. Most of these systems are about 25 years old. Mine seems to be in pretty good condition, though.

Thanks!

R.P.

Gomer · 06-15-2003, 11:09 PM

STEG it is!

Yes, the basin typically would be below the basement floor with a lid flush with the floor. Picture it as a basin like a sump pump would have (2' diameter, 3' deep or so). It probably holds around 30 gallons like I said before.

The pipe out to your septic tank (assuming 40' of 2") holds around 7 gallons of water. When the pump runs it probably is set to pump 20 gallons out of the basin and shut off. When the check valve fails, that 7 gallons of water flows back into the basin, so in reality, you only moved 13 gallons out to your tank. If it is 2", the check valve being bad wouldn't cause your pump to run nonstop like that.

However if it is a 3" or 4" pipe, a lot more water will flow back. On the order of 16 gallons for 3" and 28 gallons for 4". That would indeed cause it to cycle because so much of the water it pumps out comes right back.

If you can find where the pump is... use some water until the pump comes on, then stop ALL water usage in the house. When the pump shuts off, if you hear water flowing back into the basin, you can be pretty sure it is the check valve. That is probably what your friend did.

Shouldn't be an expensive repair if you have someone come out to do it... and if you are handy, you could probably do it yourself.

Quote:

I would assume so, the town refers to it as a "gravity system". We also have what is referred to as a "sewage lift station" here in town, as well.

Many pipes from houses will flow to a common low spot in the system... however, at some point it will need to go uphill again to combine with the other low spots. The lift station is just a pump deep in a manhole somewhere that can pump large flows of water to a higher elevation where gravity usually takes over again.