Designing & maintaining a grey water system, mound septic, or raised bed sepic system for cold or freezing climates:

Here we discuss design and maintenance options for grey water and septic effluent disposal systems that operate in cold or freezing climates.

While greywater systems generally work best in warm climates where the system doesn't face problems of reduced bacterial action nor the more immediate problem of freezing, even in cold climates there are several designs that have been proposed and tested that can keep a grey water system working and can prevent it from freezing-up.

Page top photo: a septic peat bed mound system at an un-developed homsite in northern Minnesota - a climate exposed to deep freezing conditions.

Greywater & Septic Effluent System Freezing or Frost Protection

In freezing climates it is necessary to protect the grey water system from freezing. Otherwise in freezing weather your grey water disposal system will stop functioning and it may also be damaged.

As you can see in this photo of a drain line being installed close to the ground surface in New York, the waste piping, both for black-water or grey water, are seldom buried below the frost line.

Protect Greywater / EffluentDrain Lines From Freezing

Usually the drain piping itself, between the building and the greywater (graywater) disposal system or drywell does not freeze.

That's because when a drain is properly pitched (1/8" to 1/4" per foot) AND if you don't have some slow leak into the drain like dripping faucets or a running toilet, a drain line in a cold climate should not have a freezing problem.

The drain line empties with warm household wastewater fast enough to not freeze-up.

That explains why often a drain line is not below the frost line yet doesn't freeze.

However, if your grey water disposal drywell is not deep enough, that could freeze solid.

A frozen drywell will then back-up into and can freeze and damage the drain line, and of course building gray water disposal will no longer work, risking a backup into the building and further damage.

Provide a Diverter Valve to Avoid Frozen Graywater or Septic Effluent Disposal System

A three-way diverter or flow director splitter can be used to split greywater, diverting part of it to the greywater system and part to the septic tank.

Where a splitter is installed on the greywater line below ground or in a freeze-protected space, in freezing weather you can set the diverter to send all grey water into the (freeze-protected) septic system, thus avoiding a frozen greywater system backup.

GREYWATER SYSTEM PRODUCTS, SUPPLIERS includes companies providing greywater receivers & flow diverters or splitters.

A typical diverter valve costs less than $100.

Shown here: a Pentair 3-way diverter valve with 1 1/2 to 2-inch ports, available from plumbing suppliers and at online retailers.

Watch out: the diverter valve must be installed in a location protected from freezing.

Watch out: To permit continued greywater disposal (sinks, tubs, showers) in freezing weather and to avoid drain line backups in the building, several writers and websites propose an above-ground greywater diverter valve and an above-grade bypass drain that will spill greywater to the ground surface should the outdoor greywater piping or system freeze.

Really? This sounds like a nice safety feature but in our opinion it's not without risk:

As you can see from our photo below, any drain line enjoying the fantasy of simply dumping water (condensate, greywater, or other water disposal) at the side of a building during winter weather is at risk of the disillusionment of freezing. When this happens the drain line can become blocked and frozen solid.

More examples of outdoor drain dumps and bypass freeze-ups are

at CONDENSING BOILERS/FURNACES - this problem is not unique to greywater drains.

Greywater system shut down for Winter

For a greywater system that will not be used during freezing weather, design the system piping so that it can be fully drained of water when the system is shut down. That means installing drain-down valves at each low point in the greywater drain pipe system and, of course, opening those valves to remove any standing water when the system is shut down.

After draining the system and assuring that no more greywater is entering the system, close the draindown valves to keep insects or critters from nesting in and clogging the drain lines.

Additional steps to prevent drain line freeze-up for portions of a drain system that are above the frost line are found

at DRAIN FREEZE PROTECTION.

Freeze-Protection of Disposal of Greywater-to-Ground-Surface Systems

Six-Inch Air Gap: Where gray water, usually treated, is being disposed-of by surface discharge (not permitted in all jurisdictions), there should be at least six inches between the grey water outlet at the surface to the ground surface, and the ground must slope away from the graywater discharge point.

The surface of the greywater disposal area should slope away from the disposal point at a 2% grade or better. For readers without a calculator at hand, a 2% slope is 1/4" drop per foot of horizontal distance.

Even that system is at risk of freezing if there is a leak or continuous slow flow of wastewater into the greywater drain, as we warned just above.

Alternatives to cold-weather graywater / septic effluent surface disposal systems

Greywater Absorption Bed - Soakaway

Install a conventional drainfield or soakaway bed below the frost line for greywater disposal in freezing climates.

Watch out: any wastewater effluent that is released deep in soil, such as below a 6-foot frost line in southern Quebec, may be successfully disposed-of (you don't see it again) but it will not be adequately treated by soil bacteria. That's because of the low oxygen levels in soil below about 12" and still lower oxygen levels in soil when the ground above is frozen.

Discuss your greywater design with local plumbing and building officials before pouring money into the ground with your implementation.

Watch out: if your greywater system is going to accept dishwater from kitchen sinks the system is not a true "grey water system" or you could more-properly refer to it as a "dark water system" - it may not contain sewage (from toilets) but kitchen sink wastewater is high in organic material and grease, both of which can clog a soil absorption system, more-so when there is too-little bacterial action.

The clogging problem is perhaps not in the piping but rather in the soil around the absorption bed trenches.

Greywater Mulch Basins

Some writers suggest adding perforated graywater disposal piping below mulched covering to provide limited cold-weather frost protection. The argument is that a surface greywater mulch basin is far-less costly than a network of disposal piping below the frost level.

A mulch basin must be designed with at least a 2% slope down from the point of water entry, it must be protected from surface runoff, and it must be deep enough to continue to absorb waste water when its top surface freezes. Mulch may be composed of leaves, straw, wood-chips.

Size the greywater mulch basin to be large enough to handle both the maximum daily greywater flow volume plus a reserve to handle reduced grey water absorption rates in cold or freezing weather.

This would certainly be true in hard frost northern climates such as in areas of Lake County Minnesota or further north in Canada where the frost line may be 6 to 8 feet below the ground surface.

Adding organic waste to the surface of the mulch bed will increase bacterial action and the heat generated by the composting activity within the mulch, thus improving cold-weather performance of the greywater disposal system.

Watch out: disposal of un-treated greywater to the ground surface is prohibited by plumbing codes in many jurisdictions. Your greywater system may require biological treatment or post-treatment disinfection before its disposal to the environment will be permitted.

Watch out: We are cautious of this approache in hard-freezing climates: in very cold weather wet mulch can also freeze, losing insulating value and ceasing much bacterial action. ( Ridderstolpe 2007)

Greywater Disposal Into Biofilter Constructed Wetlands

Disposeof greywater into biofilter-constructed wetlands where space and site conditions and local laws permit (Jenssen 2003).

Heated Greenhouses & Vegetated Greywater Treatment Walls Indoors

Greywater can be disposed-of by use inside of a heated or passive-solar-heated greenhouse.

Svete (2012) proposes a vegetated greywater treatment wall that might work inside heated greenhouses or other structures in freezing climates.

Greywater Re-Use Instead of Disposal

Instead of disposing of grey water in a surface or subsurface disposal and absorption system, depending on the volume of greywater being produced, you may be able to re-use all or part of that wastewater.

Many sources have described re-using greywater in combined sink and flush toilet combinations or to flush toilets.

Water conservation sources and septic system design sources also discuss using greywater on houseplants or to water plants grown in a greenhouse. Because greywater contains organic contamionants and might contain lint, hair, and other fibers, possibly also containing some household cleaning chemicals, some filtration and treatment might be needed.

See details at GREYWATER RE-USE & RAINWATER COLLECTION SYSTEMS

Freezing-Climate Greywater Disposal System Design Sources

• GREYWATER SYSTEM PRODUCTS, SUPPLIERS includes companies providing greywater systems, filters, receivers, flow diverters or splitters.
• Jenssen, Petter D., and Lasse Vråle. GREYWATER TREATMENT IN COMBINED BIOFILTER/CONSTRUCTED WETLANDS IN COLD CLIMATE [PDF] In C. Werner et al (2003) Ecosan–closing the loop, 2nd int. symp. Ecological sanitation, Lübeck, Germany, GTZ. 2003.
• Jokerst, Adam, Sybil E. Sharvelle, Margaret E. Hollowed, and Larry A. Roesner. "Seasonal performance of an outdoor constructed wetland for graywater treatment in a temperate climate." Water Environment Research 83, no. 12 (2011): 2187-2198.
• Kinsley, C., K. Kennedy, and A. Crolla. "A combined reed bed/freezing bed technology for septage treatment and reuse in cold climate regions." Water Science and Technology 76, no. 2 (2017): 286-293.
• Ridderstolpe, Peter, MULCH FILTER AND RESORPTION TRENCH FOR ONSITE GREYWATER MANAGEMENT [PDF] Report for a demo facility built in Kimberley, South Africa. EcoSanRes Programme, Stockholm Environment Institute, Stockholm, Sweden (2007). Retrieved 2018/06/27, original source: http://www.mullfilterbolaget.se/wp-content/uploads/2012/03/sydafrika.pdf
  Excerpt:
  In warm climates, where freezing is not a problem, the biofilter can be constructed on ground.
• Smith, D. W., and G. W. Heinke. "Cold Climate Environmental Engineering–An Overview." Water Science and Technology 15, no. S2 (1983): 3-16.
• Svete, Lindsey. "Vegetated greywater treatment walls: design modifications for intermittent media filters." Master's thesis, Norwegian University of Life Sciences, 2012.
• Tilsworth, Timothy, and Daniel W. Smith. "Cold climate facultative lagoons." Canadian Journal of Civil Engineering 11, no. 3 (1984): 542-555.
• Uddin, Sayed Mohammad Nazim, Zifu Li, Tobias Ulbrich, Heinz-Peter Mang, Jan Franklin Adamowski, and Roman Ryndin. "Household greywater treatment in water-stressed regions in cold climates using an ‘Ice-Block Unit’: Perspective from the coldest capital in the world." Journal of Cleaner Production 133 (2016): 1312-1317.

Above: septic mound system under deep snow cover, Two Harbors MN. This mound septic is also illustrated

at MOUND SEPTIC SYSTEMS

• Uddin, Sayed Mohammad Nazim, Zifu Li, Heinz-Peter Mang, André Schüßler, Tobias Ulbrich, Elisabeth Maria Huba, Eric Rheinstein, and Jean Lapegue. "Opportunities and challenges for greywater treatment and reuse in Mongolia: lessons learnt from piloted systems." Journal of Water Reuse and Desalination 4, no. 3 (2014): 182-193.
  Abstract:
  
  This note from the field shows a novel, hybrid concept of a constructed wetland for the first time in a water-stressed region in the coldest capital in the world, Ulaanbaatar, Mongolia. After selecting a suitable household compound, an ‘Ice-Block Unit’ was designed and constructed to assess its technical performance and capacity to reduce greywater-borne hazards during 2013 and 2014.
  
  This system was based on storing water during the winter freezing period as an ice block, and then starting treatment during the summer/non-freezing period. Results showed that the maximum removal rates of chemical oxygen demand (COD), NH4+, NO2−, total suspended solids (TSS), PO4−, and Escherichia coli were up to 100%, 99%, 97%, 97%, 87%, and 98%, respectively.
  
  The effluent met the neighbouring country, China's, municipal discharge standard of A grade effluent and could also be considered restricted and unrestricted irrigation water as reported in other studies. The system has proven potential from a technical point of view and can be scaled up to community or cluster levels.
  
  This would enable reduction of greywater-borne hazards in low, middle and high income countries with similar contexts.
• Wittgren, Hans B., and Trond Maehlum. "Wastewater treatment wetlands in cold climates." Water Science and Technology 35, no. 5 (1997): 45-53.
  Abstract:
  
  The best prospects for successful wetland treatment should be in the warmer regions of the world, but studies in North America and Scandinavia show that wetland treatment may be feasible also in cooler regions. A review shows that the number of wetlands of different types (free water surface, FWS; horizontal and vertical subsurface flow, SSF), treating different kinds of wastewater, is steadily increasing in most parts of the cold temperate regions of the world.
  
  The major wetland engineering concerns in cold climates, which are discussed in this paper, are related to:
  
  (1) ice formation, and its implications for hydraulic performance;
  
  (2) hydrology and hydraulic issues besides ice formation; and
  
  (3) the thermal consequences for biologically or microbiologically mediated treatment processes. Energy- and water-balance calculations, as well as thermal modeling, are useful tools for successful design and operation of treatment wetlands, but the shortage of data makes it necessary to adopt a conservative approach.
  
  The treatment processes often appear less temperature sensitive in full-scale wetlands as compared to laboratory incubations.
  
  Several possible explanations are discussed in the paper:
  
  (1) sedimentation playing a significant role,
  
  (2) overdimensioning in relation to some constituents,
  
  (3) seasonal adsorption (cation exchange) of ammonium, and
  
  (4) temperature adaptation of the microbial community.
  
  Experience shows that cold climate wetlands can meet effluent criteria for the most important treatment parameters. To gain wide acceptance, however, we need to become more specific about design and construction, and also about operation, maintenance and cost-effectiveness.
  
  These goals require detailed knowledge about processes in full-scale wetlands, including long-term changes and response to maintenance.
• Also see additional citations atReferences or Citations

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Comment by (mod): Contributors to freeze risk in septic & graywater systems

Illustration: depth of snow cover is a key factor in septic system freeze-ups (Reed 2001) cited below.

@Walden,

Thank you for the update; your observations of a drainfield that did not freeze during cold weather will be helpful to others.

Still I would be careful about drawing too-certain conclusions based on thought-experiments and a one-site observation whose data is surely incomplete; we have no log of actual soil conditions, drainfield properties such as depth, weather patterns such as snow-cover, moisture levels, wastewater inflow volumes, mound or drainfield design details such as disposal method (gravel trench, chamber), trench slopes, gravel properties, dispersal methods, septic age etc.

In general, if we exclude sewer line freezeups traced to slow leaks into the piping such as from a drippy faucet or running toilet or condensate drain, along with excluding septic freezing or failures traced to damage such as soil compaction, what remains is most freeze problems occur in new or recently-constructed septic systems (5 years old or less), probably because of the lower level of bacterial activity in the soil.

The most-common explanation for a drainfield that does not freeze in cold weather is that it is getting sufficient active use that warm household wastewater flowing into the system is sufficient to keep it active.

I agree that bacterial action in the soil has some effect as well, though research suggests that the freeze-resistance improvement attributed to bacterial action is more-significant in septic systems that are more than five years old. Your observation is helpful but far more-difficult to quantify without actual data.

In sum we might say that the chief cause of frozen drainfields or septic mounds is the combination of a small amount of wastewater inflow, dis-use or intermittent cessation of all use, and extended very cold weather without warm-up periods. Very important related factors in cold climates such as our Northern Minnesota case include the timing of arrival and depth of snow cover, as illustrated by Reed et als. (2001) and illustrated above.

Thank you again for taking time to follow-up - working together makes us smarter.

Supporting Research on cause & prevention of graywater & septic system freezing

• Olson, K., D. Gustafson; B. Liukkonen; and V. Cook. 1977. SEPTIC SYSTEM OWNERS GUIDE [PDF]. University of Minnesota Extension Services Publication PC-6583-GO. University of Minnesota, College of Agricultural, Food, and Environmental Sciences, St.Paul, MN.
• Hygnstrom, Janet R., Wayne Woldt, and Sharon Skipton. RESIDENTIAL ON-SITE WASTEWATER TREATMENT: AN OVERVIEW [PDF] (2006). University of Nebraska, Nebraska Cooperative Extension, EC 01-798
• Reed, Jane, Barbara J. McCarthy, Jerald Henneck, Richard P. Axler, Jeff Crosby, and Heidi Bauman. FREEZE SURVEY SUMMARY REPORT: ONSITE WASTEWATER TREATMENT SYSTEMS [PDF] (2001). - University of Minnesota, Duluth, retrieved 2021/03/30 original source: https://conservancy.umn.edu/handle/11299/200924
  
  Abstract
  This report summarizes the results of an informal survey mailed to pumpers and contractors of onsite wastewater treatment systems in northern Minnesota in the spring of 2000. The survey was developed jointly by the Sewage Technical Committee (TC) of the Iron Range Resources and Rehabilitation Board and Northern Lights Tourism Alliance (IRRRB/NLTA). The purpose of the survey was to determine, in general, the types of freezing problems associated with onsite systems during the winter of 1999-2000.
  
  Excerpts:
  About 20% of the systems (75 out of 369) with freezing problems were new construction; 3 7% of the systems (137 out of369) ranged between 1-5 years old; 25% of the systems (92 out of369) were between 5-10 years old; and 18% of the systems ( 65 out of 369) were greater than l O years old.
  
  The results suggest that systems less than one-year old had a higher freezing rate as compared to systems used for more than one year.
  
  In the industry, it is generally recognized that new installations, especially those installed late in the construction season, have a greater tendency to freeze during their first winter of operation as compared to systems used by homeowners for several years.
  
  Cold septic tanks may contribute to freeze problems on some new construction, especially when wastewater flows from the home are low or sporadic.
  
  The cold, disturbed soils, and less than adequate grass cover over a newer system, likely contributes to the problem. Both grass and snow cover help to insulate the ground and the onsite system components. When disturbed soil is placed onto a newly installed system, and the re-establishment of a grass cover is not complete, the frost depth can be quite extensive, especially in years with minimal snow cover.
  ...
  Protection from the cold is an obvious solution to the problem and a normal year of snow cover in northern Minnesota typically provides much of the needed insulation. But in winters with no snow cover until late December or early January, it may be wise to provide additional insulation for system components, especially those installed at shallow depths.
  
  Although insulation adds cost to a system, it might be money well spent in those years when snow cover is minimal. Straw placed over the system at least 12 inches deep is typically effective at minimizing frost depths.
  

On 2020-06-15 by Walden - "Septic" system design to dispose of graywater with protection from freezing in Maine

We live off-grid with no running water. We hand carry our water from a spring and generate about 4 gallons a day of graywater from our sink daily and another 2 gallons twice a week for showers. We have a composting toilet so the showers/sink are the only water sources.

Currently we simply collect our graywater in a 5 gallon bucket and dump it onto our kitchen compost pile in the winter (which I am absolutely sure is as hygienic as a leachfield), but we are about to install a leachfield system to comply with state regulations.

We are relatively fortunate in living in a state (Maine) that has somewhat reasonable wastewater regulation for our situation: a leachfield is required, but not a septic tank. The system had to be designed for a 25GPD flow (At least 5x our usage level, but far less than the minimums in other neighboring states with composting toilet regulations).

All around pretty reasonable, relatively speaking.

I am currently in the process of installing this leachfield system, and am concerned that, although it will satisfy our sole legal obligation in a region with no building codes, it may not actually function. I believe it is likely to freeze or fail during the winter due to our low water usage.

The system was designed by the licensed designer as mostly above grade (the top of the two 10' pipes end up 12" below final grade). It is gravity-feed since we live on a slope.

When I asked the designer about why on earth the drain pipe wont freeze in winter (he said 4-6" of cover material is fine over the actual drainpipe), he indicated, as this article has, that "in normal use" a leachfield and its piping aren't going to freeze because of

(A) heated water running regularly down the drain,

(B) biological activity and

(C) water sloping downhill.

I believe all of these are weak arguments in our case.

(A) Our water is not heated and is usually quite a bit below room temperature, I'd estimate maybe 55°F at most, and the amount used is a very tiny amount,

(B) we only have a leachfield, no septic tank, so while there will be biological activity, the amount of graywater going down the drain may not support a robust amount of activity if the system is over-sized (which it surely is).

Overall, I can't see how 4 gallons of cold dish water a day will keep 20 square feet of leachfield piping above freezing on a subzero day, when the frost line is 4ft.

Do you feel I am overthinking it, or would you also have concerns over the system freezing? What can be done to prevent it if it does freeze? Keep in mind we don't have much/any solar-electric capacity to heat the pipe and the system is not allowed to be buried deeper and insulation is not in the official design.

I have planned on insulating the vertical section of drain pipe before it goes below-grade, but I am wondering whether that will make any difference (as the freezing may be more likely to occur during the horizontal below-grade run).

Reply by (mod) - "Off-Grid" septic or graywater system design to avoid freezing

Walden

Thank you for the interesting off-grid septic question. What I can offer is OPINION, not fact as I don't know anywhere nearly enough about your site, soil conditions, perc rate, elevations, seasonal high groundwater level, etc.

But I think you're right. I have spent some time on this same problem and continue to research and collect sources.

See details at GREYWATER FREEZE PROTECTION where I will post our conversation to invite comment from other readers.

In general, people expect the absorption system or leach field not to freeze in winter based on

1. an assumption that the system is in daily use with far greater volumes of normal daily wastewater flow.

2. an assumption (correct) that bacterial activity in the soil as aerobic and anerobic bacteria begin to break down organics and pathogens in the wastewater, will generate some complimentary heat

In Maine the frost level is 5-6 feet below grade, and in northern Maine it can be 7-8 feet blow grade.

"Water running downhill" is, for runs not too long in pipes not too cold, for water warm-enough, sufficient to get the wastewater to its destination without freezing. But that high speed movement stops when water enters the soil around the disposal piping.

Here are some follow-up questions for your licensed septic designer, whom we should figure knows more about Main septic designs that either of us:

1. Is there indeed a freeze risk at very low inflow rates, regardless of that 4" of soil over the drainfield pipe? If your estimate is accurate your daily wastewater volume is just 5 gpd.

2. Is there indeed an increased freeze risk because the bacterial action on a graywater-only system is likely to be more constrained than would be the case in a conventional septic system that includes sewage or blackwater in a septic tank?

3. What additional suggestions might the designer have to assure functioning wastewater disposal in cold weather?

Watch out: you don't want to just move drainfield lines deep into the soil. We've done that here in northern Minnesota where the frost lines can be as deep or deeper than in Maine.

The result is at best sucessful "disposal" - you dump the water and you don't see it again, but not successful "treatment" - you lack sufficient bacterial action to break down pathogens and contaminants in the wastewater because at greater depths there's not enough oxygen, so the aerobic bacteria bails out and they leave the job to just the anaerobic bacteria.

(This might not be as serious a concern with graywater if it's considered less of a risk as a contaminant of groundwaters, wells, streams etc. than blackwater.)

See WATER QUANTITY USAGE TABLES for some more-typical daily water usage rate and quantity data. None of those data will be right for the situation you describe.

Followup by Walden

Wow, quite the speedy response. This is truly like the *old* internet! An independent site not trying to sell me anything with responsible maintainers who are actually interested in the subject (vs increasing their search rank). And with anonymous comments to boot (no login or email harvesting or linking to social media accounts).

I appreciate your feedback -- it sounds like you roughly agree with my concerns (which makes sense because I formed them from reading your excellent site).

Unfortunately, there is probably little to do to rectify the situation if it indeed does freeze short of my own ingenuity. I believe the most sensible option would be to insulate the top of the leachfield with straw or woody debris (preferable) or insulation (worst case).

Oddly, the tabula-rasa engineering approach (which always works against nature rather than with it) recommended that I replace my native soil which was high in organic matter (which would have aided both in drainage, insulation and bacterial/fungal colonies) with 4" of trucked-in "clean" top soil free of debris.

Septic designs I viewed when searching for land in Vermont regularly had 2-4" of foam insulation on top of all raised beds. I'm guessing something along those lines would be a worst-case fix (but we'd use rockwool boards in our case if we had to go that route).

I probably wont be contacting my septic designer as I don't believe he would either

(A) feel he was responsible for addressing my concerns, especially pre-emptively when I haven't experienced a system freeze-up or

(B) have a solution to offer since he can't change the design other than possibly telling me to add insulation on top.

The design was based on a precieved bedrock at 24", the system can't be lowered it could only be covered more on top.

My impression is that either I am walking down a path of compliance that those like me rarely take, or that I will discover that the system in fact doesn't freeze after all.

I will note that the notion of frost-depth tables are pretty weak science. I dug my footings far deeper than my neighbors trying to follow that science but there's really no authority on it short of a probe on your own soil across ten years.

The state guide says 4 feet in our area. Old guides say as much as 6 feet. Meanwhile science-based estimations on the local weather data of air-freezing index (and HUD recommendations), put us at less than 3ft

. I've heard the best way to find true frost line is to ask a local grave-digger -- local knowledge like that is hard to come by these days, but finding some chart with no source information is quite easy.

For those like me who actually want some real data (based on either logical analysis or empiricism), the end result is basically the realization that most things short of some structural calculations are mere convention. The bigger machinery we get, the more easy it is to just make that code say "6ft" to frost line, "just in case". Does anyone really know? These codes and charts give the impression of us as a society knowing far more than we actually do.

The other people I know who don't have running water, including my next door neighbor, thought it was funny that we thought we had to get a wastewater permit and had never heard of such a thing. My guess is that no one actually applies for these primitive system permits and no designer actually designs them besides for the occasional seasonal hunting cabin which doesn't get used in winter.

That said, they allow separated leachfields for laundry graywater in Maine, which would seem to be a similar GPD, across a week, so there should be some data from those experiments, if anyone applies for them ever or if anyone ever reports back when they fail. I, of course, am the only water carrying fool who reads through the entire state wastewater code to know about these provisions.

Most of the people I know without running water just have a pipe heading into a gravel trench, buried as deep as they could stand to dig in our rocky soil. This is just for sink and shower graywater, of course. Their system sometimes work and sometimes freeze up in the winter, depending, I'm guessing, on their attention to detail and snow cover.

Fortunately their systems are easier to maintain than mine and they dump some hot water through the gravel.

I may be able to learn more from these neighbors than anyone else. I just feel a little foolish for trying to get the permit in the first place since it neither improves the environment (my old way of handling gray water I am quite positive was ecologically superior) nor does it really seem that any local authority actually cared whether we followed through with the design.

My impression is that the whole thing is a sort of 'for show' system (at the expense of me hand-shoveling quite a bit of wheelbarrow loads of sand and fill). It will be neat if it works and worst case I suppose we have a 3-season shower drain.

My pessimism shall be replaced with empiricism in about eight months and I will try to remember to *report-back* as to the status for anyone curious enough to read comments.

Odd to post this issue on a site about codes, which I believe create these problems. People ought not get electrocuted and roofs shouldn't fall in. Septic leachate shouldn't end up in the river, either.

The intention is great in many cases, but it's impossible to codify the spirit of something or a principle, so instead you end up with blunt rules that are a mix of legacy, norms and an unfortunately small amount of science.... and when you don't fit the shape of those norms, you quickly find that all those pre-made clothes are tailored wrong. That said I'm a believer in science (as a pursuit, not a static fact) so hopefully it will eventually win out over worst-case-scenario over-engineering on these things.

On 2020-06-16 - by (mod) - actual graywater or septic disposal site conditions and thus frost depth can vary considerably

Walden

Thank you for the thoughtful discussion including points you raise about the uncertainty of frost depth data.

Your future report on what happens to the mini graywater disposal field in your plan will be important and helpful data for other readers.

Anyone with broad excavation or construction experience would probably agree that actual site conditions and thus frost depth can vary considerably within any given geographic area.

Experts who develop frost-depth data cannot address those fine distinctions and are left having to give a "safe" or more general guideline.

For example in northern Minnesota where the frost depth may be 6-8 feet, moving to a narrow band of property right along lake Superior the frost depth may be much less. Similarly, the depth of snow cover alone is a significant factor in frost depth during a specific winter season.

So currently we have global warming that may be reducing frost depth and bringing an earlier thaw, confounded by more frequent wilder storms that may in some areas bring deep snow, counteracted again by changing weather patterns that may cause very cold northern air currents to dip further south into the U.S. from Canada than previously.

All of that arm-waving done, some basic principles still apply and are more stable. Adding insulation over a drainfield will be of little effect if there is very low flow of warm wastewater into the field to provide heat that the insulation is supposed to retain.

Along the shore of Lake George NY, working with another engineer (S.T.) years ago, he designed and we installed a heating system - a loop of pipe to circulate warm water along wastewater pipes that could not be buried sufficiently deep to avoid frost (solid rock, high cost). It was a bit complex and not suitable for an off-the-grid system like yours. But it worked.

A deeper graywater disposal system, drywells or seepage pits, used to be permitted in many jurisdictions and is easier to keep working in cold weather. Main still permits drywells for stormwater runoff disposal, but may not permit them for graywater. Check with your local building department to see if that's a lower-cost, more-effective solution that they would permit. (Treatment is minimal in a drywell but graywater may be more permissible than blackwater (which I'd call a cesspool not a drywell) - )

See these drywell construction examples:

DRYWELL CONSTRUCTION for STORMWATER [PDF] Maine, Portland Water District, retrieved anew 2020/06/16 original source: Part of the Conservation Practices for Homeowners Factsheet Series, available at: Maine DEP (800.452.1942); www.maine.gov/dep/blwq/docwatershed/materials.htm Portland Water District (207.774.5961); www.pwd.org/news/publications.php

Interestingly the illustration in that document is used by other states and DECs or DEPs such as in Vermont's

DRYWELLS CONTROLLING STORMWATER RUNOFF [PDF] Vermont Agency of Natural Resources ~ Lakes & Ponds Program ~ watershedmanagement.vt.gov/lakes.htm, original source: dec.vermont.gov/sites/dec/files/wsm/lakes/docs/Shoreland/Drywells_03022015.pdf

Thank you also for your nice comments about InspectApedia.com - this site has been a constant project whose first appearance was by dial-up into a custom-hosted database in the mid 1980s, pre-Internet, so I'm particularly grateful when readers find the information useful.

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On 2021-03-30 by Walden - Performance of our graywater leechfield in freezing conditions: it did not freeze

This comment is just to update you as to the performance of our graywater leechfield in freezing conditions. Our system DID NOT freeze, despite my research and common sense indicating it would (contrary to the expectations of the system designer or the inspector, both of whom just put forward the bewildering but perhaps correct explanation that "the water is flowing down so it can't freeze" -- an explanation that doesn't account for our frozen waterfall elsewhere on the property). While our winter was milder than usual, we are still in mid-coast Maine, and we still had plenty of single digit weather.

Further, as I've stated, this is an off grid hand-carried water situation: there were only about 2-4 gallons per day of unheated water low-flowing down the kitchen sink. Also, there was no water flowing down that sink for about 10 days in mid-winter when we were traveling.

Empirical evidence then seems to indicate that rarity with which leechfields freeze has nothing to do with either (A) the amount of water or (B) the temperature of the water flowing into the system. My suspicion is it is fully and completely from biological activity, even in a system that has no septic and is only working with kitchen sink levels of decomposing matter.

Keep in mind the system detail here is likely less than 12" of cover (after compaction) over a Presby EnviroSeptic pipe (also 12" in diameter). The fact that we are on ledge could perhaps cause some geothermal from the slow-to-cool mass of bedrock to warm the system, but I suspect that it's merely from the biologically active crud in the pipe and the 12" of air followed by 12" of soil on top of that crud.

Understanding that there could be enough bacterial action in our small system is easy enough when I compare it to the rarity with which our compost pile freezes deeply, but it's still a little hard to wrap my head around the water running into the system not freezing on its way there.

The pipe into the system is 2" diameter and is located at most 3" below the soil surface. It's about a 15ft run at 1/4 in 12 slope. I suspect there must be enough crud in it to keep it active, plus the water running, even though it's a very small and infrequent amount of water.

Still difficult to understand when our creek with an active waterfall has at least three inches thick of ice over it throughout the winter. But, fortunately, I needn't understand anymore. The system is built and it is empirically tested, even if its freeze-proof qualities are not explained to my satisfaction.

Thanks for your previous thorough and helpful responses. Hopefully your users will find this first-person report reassuring if any find themselves in a similar situation (perhaps an on-grid equivalent would be a rarely used separated laundry leechfield).

 

Advice fo Freeze protecting a Montreal Canada septic system

Re-Posting from private email:

I live north of Montreal. The winter months are cold and the ground freezes.
I wish to make a drainage system to dispose of grey water from my small residence
I can't find any info about this on your site

How deep does one bury drain pipe to prevent freezing
what depth would the dry well be at to allow it to function properly

Are there any other tips to building a dry well to function in extreme winter climate.
any input or direction you could provide would be greatly appreciated On 2018-06-27 - by Anon - by private email -

Reply:

Thank you for the question. Above on this page are our best recommendations. Don't hesitate to ask follow-up questions.

...

Continue reading  at SEPTIC TANK & DRAINFIELD FREEZE PROTECTION or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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Recommended Articles

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• GREYWATER SYSTEMS - home
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GREYWATER FREEZE PROTECTION found at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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