Septic systems in winter....

[311Hemi]

Pretty sure I know the answer to this, but thought I would double check. I have a new house/new septic system. I know you are supposed to not drive over the drain field in the winter, but does that go for the tanks and line between the tanks and drain field?

I have a single path that I use to circle the house with the snowmobile, and it crosses the drain line that goes to the drain field. It crosses near where the pipe connects to the tank...and I know the top of the tank is at least 2-3' down (they installed extensions on top of the tanks). There is a pump to pump the fluids up to the drain field area, so I would believe any fluid left over in the line drains back down into the tank.

[nobody05]

Snowmobiles lawnmowers heck even a car when its good and dry out are fine. What they are not designed for is when farmer Joe fires up his loader tractor to trim trees on the yard and drives through the drainfield and such is what they do not want to see.

[hawgchaser]

In my county which I'm going to assume is similar to most counties, one of the critical numbers is 48 inches. Regardless of the total length of the drain field, the lowest level of the bottom of the drain trench cannot exceed 48 inches. That means above that 48" bottom is 2 ft. of porous aggregate and the pipe topped by the top soil (black dirt). Your link between septic and drain trenches is going to be higher (shallower) than the drain pipes dispersing the septic fluids into the percolation trenches. I believe my line slopes a little over an inch per 10 ft. of line.

Bottom line is, driving over any part of the line (during winter) leading out of the septic tank, is a Russian roulette game as far as causing freeze-up problems. I'd change my route and blow some loose snow over that part of the trail crossing the line.

[BobT]

I believe the biggest concern could be the potential for freezing. Snow insulates very well but once packed down looses much of that ability. But if the system is properly installed the lines should have been sloped properly to prevent any water from sitting in the pipe where it could freeze.

[BobT]

Snowmobiles lawnmowers heck even a car when its good and dry out are fine. What they are not designed for is when farmer Joe fires up his loader tractor to trim trees on the yard and drives through the drainfield and such is what they do not want to see.

Actually I would bet your pickup truck is a heavier load per square inch than most farm tractors.

[BoxMN]

Hemi I have been wondering that since I got my septic in 08. I too am not talking about the field, but just the pipe, and just in winter, and just for sleds. So I think hawg mentioned the answer is no, don't do it. I have not so far, and hope not to, but it would be nice to have the ability in my yard.

My builder told me sleds would not be problem for mine (at least from the house to tanks), as he said it was deep deep and he also put 2" foam (4x8 sheets) over the top of it, which he said would make any frost that got down there have to go 2' out from it, and then come down at 45's to hit it, and he didn't think there was enough cold in a in MN winter to do that... gulp... but I never wanted to risk it.

But the line from the tanks to the drain field is where I always wondered about as well, and I am pretty sure he didn't put foam over that whole spam, but I guess I should ask him...

[hawgchaser]

The OP is probably in better shape than the person who relies on gravity flow, as he's putting a substantial amount of water through every time his discharge pump kicks in. However, barring the installation of a commercial pump, he will have standing water above the check valve sitting in a 2" pipe. It doesn't have to be extremely cold to freeze a "plug" of ice in a 2" diameter pipe. Your builder was wise, Box. The problem with freeze-ups has nothing to do with the the slope of the pipe...either the connecting pipe from the septic tank or the trench pipe. The problem with gravity flow septic systems is that a drip from the house, whether from a faucet or a high efficiency furnace, results in a drip in the supply and in the discharge line. Regardless of how deep the line is coming out of the house, it is probably only a couple feet deep when it gets to the inlet of the tank and only sightly deeper when it discharges from the tank. If a drip freezes, it obstructs the flow so the next drip freezes. If it goes on long enough the frozen drips create a plug. When that happens the water backed up behind the plug will eventually freeze, too. That can be a messy and expensive PIA.

Most people don't realize that more freeze-ups occur when the frost is starting to go out rather than when we're in the midst of a cold snap. NOT packing the snow over a drain line will NEVER cause a problem. Packing the snow over the line COULD create a problem.

[Ufatz]

Interesting. A family member has small home that has had troubles twice with a block in the line from the house to the septic tank. They are gone for winters and I think the drip, drip drip thing is exactly what has caused their problem. They have sump pump that takes from basement UP to large line to tank. That line also gets drip for condensation line from furnace. Twice they have come home in spring, started up normal household and BAM!...big mess in basement from back-flow due to block Steam truck etc. fixed things. I have suggested they just shut OFF water into the house for the winter, since there is no need for it when nobody there.

But they are old time Minnesota people so they should know all this stuff. Right?

[delcecchi]

Every year I read articles from the Timberjay up near lake vermilion on how to keep septics from freezing. I think those drips with no other water usage like hot showers and washing machines are a big culprit.

They need to find someplace else to drain the furnace to in the winter if they are not around. I think I have seen discussions of that here on FM.

[BobT]

A slow drip is definitely going to be a problem but the OP didn't mention anything about a leaky faucet. So how did this become part of this discussion? If the system is used regularly, the amount of water flowing from the house to the tank in most cases should be adequate to keep the pipe free of ice. One advantage of an above ground mound system is that it isn't flowing slowly and steadily like a gravity fed drain field. When the tank pump turns on it pumps a few hundred gallons at once to the drain field which helps keep the mount from freezing. This coupled with bacterial action in the mound will generate enough heat to keep things working. When we don't use the systems regularly or we have a system that is designed for a larger capacity than needed we can risk freeze up.

[hawgchaser]

My understanding was the OP was concerned about an action of his causing freeze-up. I also believe the discussion of drips and non-use as a source of freeze-up problems are relevant. Thanks for getting us back on track by answering the OP's questions about mound septic system, however

[311Hemi]

It's worthwhile info on the drip part of it for those that may have it, but your correct I do not have worries there.

The details of my system:

I have a walkout rambler, and do not have a mound system. They dug a valley in the back yard for the walkout, and off both corners of the house the elevation is higher (original elevation). The drain field is in that higher elevation that was not excavated (as are the tanks/pipe). The builder did put insulation over the pipe that runs from the house to the tanks (15' distance or so)....and that part is gravity fed. That area will never see traffic. Then I have the tanks (4 access covers), and then the pipe that runs from the tank up to the drain field over a roughly 30' span. I cross that pipe half way between the tank and drain field...so if there is no constant back flow through it that could freeze I don't think I should have any issues.

Either way, I may just take the longer way around it through the woods....just so I don't have to worry.

[Huskie]

Kind of off topic, we have a mound system, 10 years old or so, southern Mn. close to I 90. We plan on heading south next winter for a month or so. What preventative measures can you take and what do you do if the mound system does freeze up?

[BoxMN]

Huskie, just have a friend go in a couple times when you are gone and take a dump or three. Problem solved

[BobT]

Ok. The OP was asking if it would be potentially damaging to drive across the line between the house and the septic tanks. The answer is yes and no. The OP says the line is roughly 4' below grade. This is well within the frost zone so the only way to prevent freezing is to not allow liquids to sit in the lines long enough to freeze.

If the system was installed correctly nothing, solid or liquid, should remain in the line long enough to allow it to freeze under normal use. The line should have a gentle slope toward the tanks to facilitate complete draining. Too much slope and solids will not float to the tanks but will be deposited in the line and eventually cause blockage.

A slow drip or leak is not normal use. A slow leak will freeze before it can drain completely from the house to the tanks. If the leak continues it will continue freezing and the ice will build until the line is completely plugged. Flushing the toilet, washing dishes, washing clothes, taking showers, and doing other things that allow normal amounts of above freezing water to flow will keep the lines thawed and open. The lines could lay above ground and it would work the same way so long as the water doesn't sit in the pipe long enough to freeze.

[hawgchaser]

A good informative read on the causes/preventions of sewer system freeze-ups.

Freezing Problems & Septic Systems

[Walleyehooker]

The less insulation factor with snow or whatever the deeper the frost will go. That's why in cold winters with little to no snow you hear more about freeze ups and pipes bursting. You will get some heat that builds up in your septic tank which helps but sewer lines going to the tank aren't nessesarilly buried that deep in the ground. Always best to stay off of it if possible.

[Walleyehooker]

New toilets also don't use as much water so I will hold down the handle when I flush to release more water or sometimes even flush twice.

[Huskie]

BOXMN: Good advice, I have a couple of friends that are well qualified in that area, Phd types!!!

[hawgchaser]

Huskie, just have a friend go in a couple times when you are gone and take a dump or three. Problem solved

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