Septic system filter plugs often

[BigBlue1]

I have a rural property with a septic system that doesn't seem to work as well as it should.

Background is that it was installed in 2004 and passed county inspection in 2016. Sized for 4 bedroom house (which it is) at 600 GPD. First tank is 750 gal, second tank is 1250. There is a plastic filter between the tanks that needs to be cleaned occasionally. Mound system drainfield. We always have 2 people in the house. Every other week it increases to 3 or 4 (teenagers). We don't do excessive laundry, probably average less than 3 showers a day even on busy weeks. No other significant water inflow beyond typical kitchen and toilet. Don't put anything suspect down the drain like food waste (i.e. no in sink garbage disposal and no grease down the drain). Had the system pumped out several times since 2016. Always been told system looks great and no excess build-up.

Symptoms are that every 1.5 to 3 months the filter gets plugged up and causes the level in the first tank to increase, sometimes to the point of backing up into the drain in the lowest level utility room. We've always caught it quickly and never had it go beyond the drain area (have a leak detector since the first time it happened). I've taken to cleaning the filter proactively every 2-3 months, though I was told by the septic guy when we moved in that annually should be fine. Filter plugs with what looks like potting soil consistency stuff. Black, somewhat granular. I spray it off and we're good to go mostly, but sometimes it plugs before my next scheduled cleaning. My septic guy tells me he has no real idea why this happens except that he thinks the system is not large enough.

Does anyone have ideas on why this situation occurs? Is it really not big enough for what averages to fewer than a 3 person household? If that's the case I'm certainly not going to put in a new system for $20K+... I'll just increase my filter cleaning frequency. But it seems like something else is wrong because I know of nobody else with a septic system that has these issues. I talk to people who never do anything with their system other than pump it every 3-4 years.

Thanks.

 

[mrmikey]

You use powder laundry detergent? I'm not a septic person but I do remember reading about powder laundry detergent is bad for septic. Hope you figure it out, I can imagine it'd ba annoying as he77.............Mike

 

[BigBlue1]

Nope, liquid detergent.

 

[herm0016]

i'm guessing a bit. on a high use day, you are turning that first tank and it does not really have a chance to settle out, it seems like the filter should be between the 2nd tank and the field. is the there a pump in your system? around here, we use a single large tank. we have a 4 bdrm house and a 1500 gal tank with 2 baffles and a filter thing on the outlet of the tank. no pump.

 

[BigBlue1]

There is a pump to move liquid from 2nd tank to the mound drainfield. I'm told the filter between tanks is so any solids stay out of 2nd tank and, therefore, out of drainfield. There may be 2 sections in the 1st tank with a baffle - not sure. No other filter that I'm aware of.

 

[dodge man]

Has it been pumped lately? Funny, my septic guy said powdered detergent is better.

 

[BigBlue1]

Pumped in late 2016 after we purchased the place and then again in 2019, I believe. This issue has been with us since we got here but does seem to be a little worse in the last year and a half.

 

[user.69169]

Got dishwasher machine?
Powder detergent fer dishwasher creates stuff looks like black sand. Real good for plugging pipes.

Got water softener machine?

Read up on detergents and necessary temperature for detergent to function grabbing grease and haulin it off.
Detergent gets to tank temperature change cause detergent to drop what it carried.
Whole different thing from how soap works.

Be happy flter grabbing de crud, much cheaper den crud going into mound lines.

 

[BigBlue1]

Have a dishwasher. We use liquid detergent in it (Cascade liquid).

We do have a water softener.

Definitely understand that a plugged filter is is preferable to a failing mound drainfield. Except when it backs up into the house. :-(

 

[4570Man]

I think they installed the tanks backwards. The bigger one should have been the first one.

 

[ponytug]

Sorry to hear about your troubles.

Because you are finding the grit on the outlet flow, it has to be close to the density of water, which to my mind rules out detergent powders and water softener resin.

Your description of the usage and total tank size seem ok, but the tank arrangement is a new one to me. I agree with 4570man that normally the larger tank would have been first. Mostly septic tanks are there to settle out solids. Any anaerobic fermentation is a bonus, unless you have an aerobic system which will get rid of almost everything.(See below)

How is your water usage? Low flow toilets/showers/front loading washer? Or lots of baths/top loading washer? Is your softener plumbed to drain through the septic tank? If you use lots of water, you may just be flushing solids through your small tank faster than they can be digested.

Is it possible that the tank outlet is emptying from close to the bottom of the tank? It should be just a few inches under the surface.

Unless you have some huge excess amount of grease coming through, and I would think that your septic tank pump guy would have commented on it, I am inclined to think that the tank configuration is off.

If you aren't using large amounts of water, I would be inclined to consider converting the first tank to aerobic digestion.
https://www.tractorbynet.com/forums...y-septic-system-experiment-1.html#post5899907

If you are using lots of water, I would be inclined to try for low flow first.

All the best,

Peter

 

[4570Man]

.

Your description of the usage and total tank size seem ok, but the tank arrangement is a new one to me. I agree with 4570man that normally the larger tank would have been first. Mostly septic tanks are there to settle out solids. Any anaerobic fermentation is a bonus, unless you have an aerobic system which will get rid of almost everything.(See below)

,

Peter

Septic requirements are obviously different where he lives and where I live but here they would never spec a 750 tank for 4 bedroom. It’s 900 gallon for 3 and less and 1000 gallons or more for more. I feel fairly confident the OPs tanks are backwards. A pump tank really only needs to be big enough for the pump to fit. A 50 gallon barrel would work. The downside is the sewer would back up almost immediately in a pump failure. They make them bigger to allow for more time to fix the problem before failure.

 

[Firemanbuck]

I had a similar setup, but the filter was on the outlet of the tank to the dosing (pump) chamber. Too many solids in the first tank for a filter. Not surprised it's plugging up.

 

[hosspuller]

Here's a thought when you check the filter collect the crud in a bucket of water. If the stuff settles out, then your first tank isn't doing the job of separating water from the "stuff" or the inlet flow is being directed to the outlet filter. Either way ... no or insufficient settling is taking place.

 

[BigBlue1]

I was reading the original spec sheet wrong. The pump tank is listed first so I just assumed the sizing was based on flow layout. It is actually 1250 'septic tank' and 750 'pump tank'.

We don't have low flow toilets and we do have a top-load washer, but we had a front load washer for the first couple years and the issues were still there. We try to be conscious of water usage so I don't think we're excessive for a 3 person (average) household.

 

[ponytug]

Great to hear that the 1250 is first. It doesn't sound like you are over using water then.

Hmmm...I am not an expert, but it seems like something is stirring your main tank up. Normally, there are elbows at the outlet to take effluent from a couple inches below the surface. Is yours still there? If not you might want to put in an exit "Tee" to see if that helps.

FWIW: we have a 1300 gallon tank, with a baffle (basically a 2x650). The liquid has always been crystal clear in both halves, with a few items floating in the first half, and nothing visible in the second. My exit filter which is basically a nylon brush in the exit Tee hasn't been cleaned in 12 years(ish), and when I had the tank pumped last 13 years ago, there was essentially nothing at the bottom of the second tank.

All the best,

Peter

 

[RoyKing]

Try using a biocide, bleach, dishwasher, water softner could be killing the tank.

 

[oosik]

Your 1250 gallon septic tank should be two compartments. Have it checked, or if you know what you are doing, check yourself. There MUST be an outlet T or baffle between the first compartment and second compartment AND there must be an outlet T or baffle on the outlet of the second compartment. Properly installed and still in proper working order - large volumes of fines WILL NOT pass out of the septic tank.

Thank your lucky stars - the filter IS working. Otherwise all that fine material would end up in your mound system and be plugging it.

The fact that you are getting large volumes of fines in the filter indicates that all may not be well.

Have the septic tank checked by somebody that knows what to look for. It could be that the septic tank needs to be pumped. A "full" septic tank does not allow sufficient time for solids/fines to settle out.

 

[seville009]

i’m just a homeowner, not a septic expert, but why in the world would there be a filter in the septic line? What is it that needs to be filtered? Solids stay in the tank, liquids flow to the leach field, and solids get pumped out every three or four years.

Seems that sticking a filter in the line would invite clogs; what has to be filtered?

 

[oosik]

Fine organic matter can pass out of any septic tank. These fines are what can plug the gravel in a drain field. The filter stops these fines. I check my filter every six months. There is VERY LITTLE organic material on the filter.

Think about this - if it were just plain liquid passing to the drain field - - the drain field would NEVER need replacement. It's NOT just plain liquid. This liquid contains organic matter. This organic matter forms into mat growth in the gravel and will, over time, plug the gravel.