confusing/problematic failure to pump effluent

[ColoKevin]

I've searched past threads and can't find a prior discussion of this problem, but I'm hoping someone has seen it before.
We have a 3-chamber septic tank, with a pump. All relatively new -- installed 4 years ago; pumped a year ago.
This winter, the alarm went off and we found that the pump wasn't clearing the effluent to the leach field. We replaced the pump, but the problem continued. The plumber conclude that the winter weather had frozen the ground -- frozen the water around the perforated pipes.
Eventually, when the weather warmed, the system did start working again. But several weeks later, the problem returned. It's not clearing (again).
I've had three plumbers with septic-system expertise look at it, and everyone seems puzzled. They've explored blockages and cracks/breaks. None of those panned out.
In researching this online, I see a discussion of biomat build-up. But what I see assumes backups inside the house or at the top of the field (marshy conditions) -- none of which happens here. It's just that the third chamber doesn't drain. Could the problem, however, still be biomat? If the draining isn't working, maybe it's too flooded down there for the pump to push in new effluent? But wouldn't I then be seeing the marshy conditions?
As a homeowner, I've apparently screwed up by failing to maintain the system with various product (and haven't cleaned/replaced the filter before the 3rd chamber). I'm just learning about that now.
But at this point we need to figure this out or we can't live here (without using drains!). Do we need to dig up a 4-yr-old system?

 

[Twowaxhack]

You may have a failure or you may be using too much water for your field to take on. If your water is metered, how much are you using per month that goes into the tank ?

You’ll need to access the entry of the pipe into the field to see if the problem is the field or the pipe leading to the field. I suspect the field is waterlogged.

You may have a distribution box where the lines branch off into the field. Maybe not….

If the water entering the field is not being distributed properly then you’re not taking advantage of the entire drain field, you may just be using a small portion of it.

 

[ColoKevin]

Thanks. Yes, that was one of the possibilities we looked into. We dug up distribution box and cut out a piece of pipe (to look around for blockages). It's being distributed to (and past) all four flushing valves.
The system was designed/built for 500+ gallons/day. I can't imagine we're using more than 200 gallons/day. (We do have a meter, and we vary between 4-6k/month.) But I do keep returning to the "too much water" answer -- it just doesn't seem to make sense given that the system was built for so much more use.

 

[Twowaxhack]

4k gallons of water a month is what we shoot for in my area. Some areas are better than others of course.

I suspect part of your drain field is not working and there could be a lot of reasons why.

Is it possible that your pump is flooding the field ? Maybe make the pump come on for smaller doses to the field.

For example, your pump may be pumping 500 gallons a cycle……shorten that cycle up to 100 gallons or 50 gallons. Maybe that’ll give the field time to rest between cycles.

That’s just a guess……it all may be set up perfect.

 

[Twowaxhack]

Many times I’ve removed the washing machine from the system and utilizing a separate field line to carry this load.

That solves the problem where a lot of clothes washing is done.

Worked at my house

 

[ColoKevin]

Removing the washing machine would be interesting. Just treat that as grey water and send it into the yard?
Anyway, I just tried to "manually" run the pump after it was off all night. In 10+ minutes, it cleared no noticeable amount.

 

[ColoKevin]

The new working theory is that here in CO (or at least Boulder County) they want the holes to be only 1/8" diameter. So the biomat could be creeping into those holds -- blocking them up.
With that as the hypothesis, the best suggestion seems to be jetting, followed by a clean-water flush.

 

[SHEPLMBR]

Do you have a control box? Did they check the floats?

 

[ColoKevin]

Yup. (the floats are working well)

 

[ColoKevin]

To close this out and to help others who might find this thread through a search, the problem seems to have been Colorado-specific. Here in Boulder County and apparently in many other counties throughout the state, they have moved (under pressure from the state) to 2" pipes with 1/8th inch holes) -- and the holes are easily clogged with the biomat material. So other than digging trenches over the pipes and drilling additional holes, the solution seems to be regular flushing and jetting.
My understanding is that the state/engineers moved to the 1/8th inch holes as a way to keep the pipes pressurized enough so that the effluent is evenly distributed to the full system of pipes.
I hope this helps.