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Thread: Woodworking with a septic system

  1. #1
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    Woodworking with a septic system

    My brother just bought 10 acres outside Austin TX and is building his retirement house. I guess they don't have basements in Austin because he's taking over the two car garage for the shop he never had before.

    As you might guess, with 10 acres, he will be on a septic system. He and I discussed the advantages of a slop sink in his shop and also I pointed out that he has to be careful what he puts down the sink. I directed him towards my favorite water born poly (Vermont Natural Coatings Polywhey) which is safe for septic (VNC says so, anyway). We talked about cleanup.

    Are there any other gotchas or hints for having a shop and a septic system?

    I'm used to cleaning brushes with mineral spirits and then following up with soap and water at my sink to get the last bit of paint and MS off. Can he do that with a septic system?

  2. #2
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    I had aerobic septic for previous house. Solvent-based waste was left in open top container to evaporate, or poured into a trash bag of sawdust (if I was in huge hurry). Water-borne was just washed into drain, except for ~3gallons of old latex paint. ...I thought that might upset the bacteria?

    Anaerobic septic may be more sensitive, but is mostly supposition on my part.

    I doubt 1/4 oz of MS diluted & rinsed out of a brush occasionally, would be a ‘killer’.
    Last edited by Malcolm McLeod; 04-15-2019 at 2:29 PM.
    Molann an obair an saor.

  3. #3
    There are at least two things you want to avoid: killing off the bacteria and plugging up the drain field. I avoid dumping any solvents or harsh chemicals of any kind into the system. Those are left to evaporate, or are sent to hazardous waste facility. I use buckets of water to clean things like brushes and rollers used with paint or clear water born finishes and especially things like drywall compound or anything that sets up hard. I wait for the solids to settle out, pour the water off out in the yard somewhere, and then put the settled solids in the trash. The solids in stuff like paint and drywall mud can plug up the drain field over time, and even things like lint from the washer. Newer septic systems usually have a filter between the tanks and the drain field. I'd recommend having one added if his system doesn't have one. Way cheaper than replacing failed drain field. It's a lousy job to clean it, but doesn't have to be done often.

  4. #4
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    We have a septic system, but the sharpening, and catch-all sink in the shop empties into an Azalea bush outside the wall. 1/4 0z. of solvent won't hurt a septic system though, or at least not enough to worry about. Any solvent cleaning here is usually done outside, over a catch pile of sawdust.

  5. #5
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    Quote Originally Posted by Malcolm McLeod View Post
    Solvent-based waste was <snip> poured into a trash bag of sawdust (if I was in huge hurry).
    I would be very concerned with spontaneous combustion if doing this. As it dries it gives heat off and the sawdust self insulates and poof... a fire. Across town a brand new house burned down from a pile of rags after finishing the floors. And growing up on a farm, we never put wet hay in the barn (and even larger piles of coal, or wood chips, will self combust)

    As for septics - I put nothing down mine that isnt easily biodegradable. (I dont even use the garbage disposal much, although that might be overly conservative). My approach is similar to Paul.

  6. #6
    Quote Originally Posted by Carl Beckett View Post
    I would be very concerned with spontaneous combustion if doing this. As it dries it gives heat off and the sawdust self insulates and poof... a fire.
    Popular misconception here. There's a big difference between 'dry' and 'cure'. Mineral spirits evaporating does not generate any heat; quite the opposite, it actually cools because of the heat taken to evaporate it. Oil base finishes that cure by polymerization will generate heat when curing that can lead to fire. Rags soaked in mineral spirits and finish need to be treated as though they could start a fire. But rags soaked with mineral spirits that were just used to degrease or dewax a surface do not pose that hazard.

    I know, I'm being a little pedantic, and of course, it doesn't hurt to treat them all as though they could spontaneously combust.

  7. #7
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    I don't dump any solvents down my septic system. I have a pile of fireplace logs that I'll pour it over.

    After I use a solvent (like paint thinner) to clean a brush, I'll take a paper towel and wipe it off. Then I use an air hose and blow off whatever is left. Then I'll use soap and water (that goes down into the septic) for the 1% that is left. So maybe 2 or 3 drops of thinner (or less) make it to my septic.

    I also avoid putting latex paint related effluents into the septic as they often contain things that the septic doesn't like.

  8. #8
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    Do not put anything into that septic system you wouldn't put down a normal drain,and that includes any fatty substances like bacon grease, cooking oils, butter, etc.
    Water, grey water with septic approved cleaners, toilets, and food stuffs that can break down, Nothing else. You need live bacteria for the tankk to doit's job.
    By the time he flushes the toilet for the 1st time, that septic system will cost as much as a new car. Digging it up and repairing it will cost as much as a new truck.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

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    Quote Originally Posted by Frank Pratt View Post
    Popular misconception here. There's a big difference between 'dry' and 'cure'. Mineral spirits evaporating does not generate any heat; quite the opposite, it actually cools because of the heat taken to evaporate it. Oil base finishes that cure by polymerization will generate heat when curing that can lead to fire. Rags soaked in mineral spirits and finish need to be treated as though they could start a fire. But rags soaked with mineral spirits that were just used to degrease or dewax a surface do not pose that hazard.

    I know, I'm being a little pedantic, and of course, it doesn't hurt to treat them all as though they could spontaneously combust.
    You may be right, this warning suggests the reaction is oxidation.

    https://www.newpig.com/absorbent-tra.../8036?show=All
    http://www.mfs.sa.gov.au/site/commun...combustion.jsp

    That may be the same for putting up wet hay in the barn... a no no.

    There are many that get away with piling rags for years. Which doesnt mean it is a good idea. After reading a bit, I could not accurately tell you which materials oxidize and which do not....

    So I still think it is a bad idea.

  10. #10
    Quote Originally Posted by Carl Beckett View Post
    You may be right, this warning suggests the reaction is oxidation.

    https://www.newpig.com/absorbent-tra.../8036?show=All
    http://www.mfs.sa.gov.au/site/commun...combustion.jsp

    That may be the same for putting up wet hay in the barn... a no no.

    There are many that get away with piling rags for years. Which doesnt mean it is a good idea. After reading a bit, I could not accurately tell you which materials oxidize and which do not....

    So I still think it is a bad idea.
    Yes, if there is any doubt, treat it as though it will catch fire.

  11. #11
    Quote Originally Posted by Frank Pratt View Post
    I know, I'm being a little pedantic, and of course, it doesn't hurt to treat them all as though they could spontaneously combust.
    No you're not. I have a friend who restores cars his garage caught on fire due to some oil soaked rags left in a drum.

    The losses were tragic. Insurance money couldn't replace most of it.

    I lay my rags either on the rim of a garbage can or hung up on a line outside the shop. When dry I throw then on the next wood fire.

    Although you shouldn't send solvents into a septic system, its really a matter of proportions. I seriously doubt a quart of mineral oil into a 1000 gallon septic tank is going to do any harm.

    The other option is to have a dedicated sink for solvent use that drains into a container which can be taken to a local hazardous waste disposal site.

  12. #12
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    It's just as illegal and dumb to put solvents into a septic system as into a city sewer. They belong in a hazardous waste container, to be properly disposed of. If you're a business it's a matter of hefty fines (they can and have run to $100K's) for violations and you need to use a commercial service, readily available in most places. For non-businesses, most municipalities schedule hazardous waste days when they will take such materials, usually for free.

    There have been some pretty impressive explosions resulting from combustible waste being dumped into a sewer. If it's a septic system do you really want to be dumping that stuff right back into your drinking water supply?

  13. #13
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    Quote Originally Posted by roger wiegand View Post
    It's just as illegal and dumb to put solvents into a septic system as into a city sewer. They belong in a hazardous waste container, to be properly disposed of. If you're a business it's a matter of hefty fines (they can and have run to $100K's) for violations and you need to use a commercial service, readily available in most places. For non-businesses, most municipalities schedule hazardous waste days when they will take such materials, usually for free.

    There have been some pretty impressive explosions resulting from combustible waste being dumped into a sewer. If it's a septic system do you really want to be dumping that stuff right back into your drinking water supply?
    Roger, All good points. Particularly that last one. My brother will get his water from a well on the property.

    Where I used to live in the Kansas City area, I knew of no hazardous waste days. I thought that really odd. To dispose of hazardouse waste in Johnson County, you had to call for an appointment, usually two weeks hence. Then you had to drive to this one place where there was a locked gate. You pressed an intercom button and waited. I've waited several minutes. A very bored person will open the gate and tell you to proceed and you get rid of your stuff.

    Here in Fairfax County outside of DC, it's a lot better. I still know of no hazardous waste days. There are transfer stations open 7 days a week. You drive up to what looks like a toll takers booth, tell them you have HW and they wave you through. Some very nice people help you unload your stuff. Muuuuuch better.

    I keep bottles of clean and dirty mineral spirits. The dirty bottle settles and I start cleaning my brush with that. Then I change to clean MS and dump as much as possible into the dirty. When I'm happy with the MS step, I use a paper towel or rag to remove as much mineral spirit as possible and finally wash with soap and water in the sink. Some solvent goes down the drain but not very much.

    The point I made to my brother about Vermont Natural Coatings is that the stuff is made from milk products and I was assured by the mfr that it would be safe for the septic system. But you make a really good point about whatever is going into the septic might eventually end up in the aquifer.

  14. #14
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    Quote Originally Posted by Frank Pratt View Post
    Yes, if there is any doubt, treat it as though it will catch fire.
    I think there is more to this than whether there is doubt. A lot of accidents happen by over confidence in ones own knowledge.

    So some solvents (definition of what is a 'solvent' I will skip) wont oxidize, but some will. Including it seems, wet sawdust. So simply putting water in a pile of sawdust could cause combustion (like wet hay or compost). Certainly in my case I would have guess mineral spirits in a pile of sawdust would have been a higher risk than water in a pile of sawdust - but I might have been wrong (I am wrong a lot). I also thought it interesting that laundry mats catch fire due to this.

    I still think its a bad idea. Whether you are 100% confident or not. (it is that over confidence that is the wild card)

    Turns out many of my searches on the subject led me to posts here in SMC
    Last edited by Carl Beckett; 04-16-2019 at 10:26 AM.

  15. basically, just dont kill your friendly bacteria.
    anything harsh gets put in old sauce jars and thrown out.This is very little I use things till they're gone.
    I use foam brushes and toss em with bad stuff.
    Latex paint brushes can be cleaned as long as it s just a few times a year.
    I bleach my homes piping because our well is very heavy in iron but I only do this once a year at most

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