13

I live in a housing addition (built 1965-1980) in the barren (no trees) Oklahoma panhandle. The first thing the new home owners in this area did was plant as many trees as possible.

Over last several years in my neighborhood many of these house sewer lines out to the alley main line are being dug up to replace either rotted (cast iron tree rooted pipe) or collapsed schedule 20 PVC (yes 20 not 40 schedule).

I guess my line is PVC because bent cloths-hangers & rented metal pipe finders won’t even blink to indicate cast iron. So knowing that at any time now it will be my turn to destroy my heavily treed back yard to replace my sewer line.

This town is trying to die & most plumbers have retired or moved off & not one of the remaining plumbers has a camera or pipe line sensor to run down the closet toilet to locate the line out in the yard. Also, there are no clean outs in yard which could indicate where to start digging.

My Question:

The next time it snows, if I pull the toilet off of the closet flange, configure a 4” to 24” square metal HVAC pipe duct funnel, set a 24” x 24” box fan on top of funnel, turn the central heat up sky high & blow hot house air down funnel into sewer line, would I be able to melt the snow so I can see where the pipe runs?

Machavity
  • 23,184
  • 6
  • 41
  • 90
Oily Tex
  • 379
  • 2
  • 11
  • 27
    Hot water would do better than hot air and not involve any yanking toilets and letting sewer gas into the house - try doing several loads of laundry that use hot, run the dishwasher or do the dishes, take a hot bath, etc. - but not likely to show up from 3 feet down, really. Drive to someplace that rents the tool you need is more likely to work. – Ecnerwal Jan 31 '23 at 18:16
  • 6
    Should work in a couple of weeks. Imagine the ground is quite frozen solid by now, so you need to warm the pipe, the ground before any snow will start to melt. The city/town might maps of where the house sewers connect to main pipe. The line should be in a straight line from where exits the house to there. The exit from the house will be a good starting place for digging. – crip659 Jan 31 '23 at 18:16
  • 4
    Why do you need to pop the toilet off the flange? Just remove the toilet seat and you should have a nice flat surface for a piece of plywood and some caulk. When done, the caulk will release cleanly from the porcelain enamel. However your bigger problem is the sewer vent pipes all over your house. Hot air will simply go up those. That's where water has the edge. – Harper - Reinstate Monica Jan 31 '23 at 21:20
  • 1
    I can't imagine that this could possibly work. Unless the pipe is very close to the surface, its heat is not going to be enough to melt the snow. And even if there was enough heat, it would be spread over too large an area to make this a useful technique, even if you use hot water rather than hot air. – Dawood ibn Kareem Feb 01 '23 at 05:49
  • 7
    Oily Tex, Consider if the heat of the heated drain pipe could significantly affect the snow cover, then the snow cover could affect the drain pipe. IOWs, it this works, the drain is not deep enough to prevent its freeing during normal usage. – chux - Reinstate Monica Feb 01 '23 at 14:38
  • 2
    For what it's worth, I've lived in three different houses with septic systems and a snowy climate. In every case, the location of the septic and pump tank was very clear soon after a snowfall, but the location of the sewage pipe from the house to the tank was never visible. I think it's just too deep. – Mark Feb 02 '23 at 00:37
  • Mark. My my intentions were to add 2 bath tubs full of very hot water down the 35 ft sewer line out to the alley, hoping to get a visual on at least some small impression of melted snow. – Oily Tex Feb 02 '23 at 01:17
  • chux - Reinstate Monica Chris H My thinking is that the heat from the hot water energy would tend to migrate upward as heat tends to rise, but don’t think that the cold from the snow cover would freeze the drain pipe buried 3 ft down, as where I live ( Guymon Ok) we have a 18” frost line, plus we usually get snow between ( 31* - 28*) & melts over (1-2) days. But all things are valid to consider with Mother Nature LOL. – Oily Tex Feb 02 '23 at 17:07
  • 1
    While out hiking yesterday, I came across a buried natural-gas pipeline that had melted the snow above it. The centerline of the bare patch was plus or minus about five feet of the marker posts, so depending on the accuracy you're looking for, this might not be viable even if you can get enough heat down there. – Mark Feb 19 '23 at 21:22
  • Mark Mark yes, for 40 yrs my job as a drilling supervisor was to operate ( drilling, completion & workover rigs ) over top of hundreds of burried gas lines with gas flowing to surface from 1,000s of ft deep in the HEATED EARTH. This is where I 1st got the idea, as I saw lots of melted lines covered in deep snow, melt from the heated gas flow through them. You could look down those lines for a 1/4 mile & see where they were hidden in the soil. – Oily Tex Feb 19 '23 at 21:54

5 Answers5

34

I doubt that you could get enough heat into the sewer line to melt the snow on the surface. Even if it did, that would only give you a vague idea where the pipe run is, though it would be more accurate than nothing.

I've got two alternate suggestions:

  1. Ask the city. They'll know where the main sewer line is and, most likely, they'll know where your house is connected to it. Once you know where that point is, it's highly likely that the drain line runs straight back to the house in the shortest distance possible. Construction companies don't like to waste time and material making random routes when a straight line will do.

  2. Rent a snake long enough to reach from your toilet to about 1/2 down your back yard. Run the snake down the drain, then use a metal detector to find the snake. Once you've got a good idea of location and direction, it's probably safe to presume that the run will continue in a straight line unless there's an obvious obstacle (that was there when the subdivision was built, not something added afterwards).

FreeMan
  • 37,897
  • 15
  • 71
  • 155
  • 4
    DUH, ! ! !, WOW, OK. That’s so simple. Just pull toilet & run a snake down 4” line & out under back yard. Go back to United Rental @ Liberal Kn & re-rent metal detector. Flag the high toned beeps out to the alley. Problem solved. FreeMan, I know I’m not supposed to say THANK YOU, but I can’t help it ( THANK YOU ) also to crip659 & Jack. You guys are the best, Oilytex. – Oily Tex Jan 31 '23 at 19:43
  • 3
    @OilyTex: We just ask that you make the thank yous in comments, no thank you "answers". :-D – Sean Duggan Feb 01 '23 at 03:25
  • 1
    You might want to look at a utility locator with a separate "toner" (cable line transmitter). You attach the toner to a metal pipe or in your case a drain snake and it turns it into a radio antenna broadcasting a signal. The utility locator can then detect the signal more accurately then the metal detector method. – John Ray Feb 01 '23 at 07:49
  • 1
    They even sell (and probably rent out) pipe locators. I don't know how accurate they are (never used one) but it sounds pretty promising. – iDriveSidewayz Feb 01 '23 at 14:55
  • 1
    Option 2 above is how they figure where to cut the sewer line for a plumbing disconnect in my city. – shoover Feb 01 '23 at 15:43
  • John Ray, yes your correct. When you rent a GOOD metal pipe detector set, many of them come with a (battery / tone sensor) that you attach to either the metal (csg, tbg or in this case would be the metal snake) that sends a signal transmission for the metal detector to pickup. They work good with any conductor to generate a electric field path. – Oily Tex Feb 01 '23 at 19:37
  • I DriveSidewayz, yes can even rent them at the big box stores. They work pretty good, but tend to pass over buried ground conductors more than 3 ft deep. There inexpensive ( $40 ) a day & work fairly good to find metal sewer, gas & water pipes. – Oily Tex Feb 01 '23 at 19:44
  • Sean Dugan Need to put Thank Yous in (this) comment section. Got it, thanks, Oilytex. – Oily Tex Feb 01 '23 at 20:03
  • 1
    Frankly, @OilyTex, an up vote on _all_ the answers you found helpful and a check mark click for the one you found _most_ helpful is all the "thanks" necessary around here. – FreeMan Feb 01 '23 at 22:21
  • 1
    I second @FreeMan's suggestion, but in the event of continued problems I'd suggest watching out for any change in grass colour particularly in late Summer: whether or not the pipe is leaking, disturbed ground can have an effect on the way things grow for many years. Also getting a drone and sending it aloft at Sunset to look for any shadows caused by subsidence can be very effective. In extremis, hire a soil resistivity meter: I've seen one of those used to map out Roman ruins so a recent drain should be no problem. – Mark Morgan Lloyd Feb 02 '23 at 15:05
14

Tl;dr: physics says it's going to be very expensive.

Lets run some extremely rough numbers. This is going to approximate a lower limit on the heat required - you're likely to need far more. I've rounded massively, and more often than I should.

I'm going to assume a pipe buried 1 metre down, in soil that's at 0°C covered with a thin layer of frost/snow - just enough to indicate the temperature rise by melting.

The volume of soil that needs to be thawed will be considerably greater than the volume between the pipe and the surface, as the ground will conduct heat in all directions equally. I'm going to say you need to thaw a 3 square metre cross section (πr² with r=1m from the depth, rounded).

Dry soil has a density of around 1200kg/m³; the moisture content is likely to be 10-50% of this. With rounding that means 100-500kg of water per cubic metre, or 300--1500kg per metre of pipe run.

The latent heat of melting of water is 334kJ/kg, call it 300kJ/kg. That means for each linear metre of pipe, just to thaw the water in the soil if it's already at freezing point, you'll need 90--450MJ. 1kWh is 3.6MJ, so you'd need to deliver something like 30-150 kWh per linear metre of pipe.

This will go up if the soil is colder than freezing point, but not by all that much. The specific heat capacity of ice is 2.1kJ/kgK, so for each degree Celsius below freezing you'll need an extra 0.6-3MJ.

A thick layer of snow will make things far worse. Snow is a good insulator so more of the heat will go into the soil and less will reach the surface.

Lets see how much hot water you'd have to deliver to achieve that. A full bath holds the best part of 200 litres. At 60°C, cooling to to 0°C (which you won't manage) that's 50MJ (or about 14kWh, or £1.40 at UK gas prices). That means you need at least two very hot, full bathtubs per metre of pipe run.

At the price I pay converted to USD that's $3.40 per metre in heat - if you can deliver it with as much efficiency as I calculate, which you can't (and if the soil is exactly at freezing point, though this is a small effect). You could easily be into the tens of dollars per metre. You imply a fairly large plot of land, so you could well be into spending thousands of dollars on heat with no guarantee of success.

I wonder how much it would cost to hire ground penetrating radar; even with an operator it's probably cheaper and has a far higher chance of success.

Chris H
  • 5,038
  • 15
  • 25
  • 1
    BTW I can see where your thinking comes from. In my street the snow melts far quicker (or frost doesn't form) around the inspection hatches for the sewer. However instead of a big volume of soil, the heat from the pipe only has to warm a smaller volume of air in the inspection chamber. Between the covers, knowing the pipe run, I've never seen waste heat prevent frosting, even though by this point it's the waste heat from a dozen houses, and even ons night when the temperature drops only just low enough for frost to form. – Chris H Feb 01 '23 at 10:41
  • Chris H had to read your script (3) times. It’s really great, but deep. About 1 meter over my head, but evident that you’re are either ( chemical, petroleum, electrical, but I’m betting on MECHANICAL ENGINEER). In your second paragraph you give parameters of ( 1 meter down @ 0 C*). You are correct. Where I live, the center of Oklahoma Panhandle at Guymon town, most of our snow is at freezing or maybe down to 28*, so the ground barely freezes deep & the dry humidity in the winter here runs in the 20s. So I might try the hot water next time it lightly snows. I will let you know how it goes. – Oily Tex Feb 01 '23 at 20:42
  • 1
    Clarify please - do you need to do this now, in winter? Or can you wait till next spring when the ground is diggable, and then get stuck-in with a spade where the sewer line exits your house ? – Criggie Feb 01 '23 at 21:57
  • Criggie I was wanting to only (verify) the buried heated line with the melted snow from house out to the alley, then flag the line and THEN dig it out in the spring. – Oily Tex Feb 01 '23 at 22:20
  • 3
    The thing is you don't need to _melt_ the snow with the heat. What you want to do is wait until snow is naturally melting and add a little bit of energy so the snow above the pipes melts faster. – user71659 Feb 02 '23 at 00:49
  • 1
    @user71659, that doesn't gain you much. Soil is a wonderful insulator, so it takes a lot of heat to raise the temperature of the surface even a little. – Mark Feb 02 '23 at 01:19
  • 1
    user71659 That’s a good suggestion. If I waited for the melt to begin, as the ground starts to warm, then the extra hot water energy would help Mother Nature due her thang. All I would need is just a slight impression & red flag the sewer line out to the alley. – Oily Tex Feb 02 '23 at 01:22
  • If I even got just a low spot, then I could flag a line straight to the house, so the line should be hopefully in a straight line, then blind dig a test hole, – Oily Tex Feb 02 '23 at 01:26
  • 1
    @Mark Being a good insulator doesn't mean thermal energy will disappear. That would be against the laws of thermodynamics. Being a good insulator means you have to wait longer for the effects to occur. What actually matters is thermal diffusivity (proportional to thermal conductivity divided by heat capacity), you want low thermal diffusivity to allow the heat to concentrate in one spot. – user71659 Feb 02 '23 at 03:17
  • 1
    @OilyTex I only play at mechanical engineering - I'm a physicist by training (and maybe it's written for physics undergrads - but I didn't want to add any more length) . The idea of adding a little heat is a nice one, but I'm used to snow melting very patchily anyway. You mention trees; even with bare branches they cast a shadow and where there's less shade the snow will melt faster on even a slightly sunny day. – Chris H Feb 02 '23 at 09:08
  • 1
    ...But do let us know how you get on, if you try it. Note that it will take time for the heat to come out, and you'll still need a lot of heat to thaw the ground before you get to the surface. The heat will get out slowly so I reckon you'd need to put it in slowly rather than the water rushing through and still being hot when it leaves your area of interest. – Chris H Feb 02 '23 at 09:09
  • 1
    Shallow buried stuff is often easiest to find in a dry summer, but I reckon this a typical sewer is too deep to cause dry grass. Where the sewer passes under my garden, there was a slight depression caused by the backfill settling. That might also be worth a look, perhaps when the sun is low in the sky to cast longer shadows, (but the trees won't help with that) or with a drone. – Chris H Feb 02 '23 at 09:11
  • 1
    Chris H Thanks for the continued support. I figured you were in one of the (4 ) disciplines, as I worked with many over 40 yrs of oil rig drilling, but my company only sent me the physicist to the rig on the WILD CAT oil plays. Anyway thanks again & I will let you know if I find the line. – Oily Tex Feb 02 '23 at 12:24
10

I seriously doubt that running air from your heating system down a pipe 36" below grade in freezing weather will melt snow at grade level. Most counties, townships, etc., have phone numbers to call for locations of underground facilities. Try them. Check with other neighbors and see how their pipes were run in relation to their toilets and out their walls and make an educated guess on where your pipe exits the wall and dig a small hole to verify a location. Fom there, dig along the exposed pipe to the alley. You could also try contacting separate underground location companies. Some can run a sensor thhrough the pipe and then trace the signal above ground.

JACK
  • 72,186
  • 15
  • 68
  • 170
  • Ecnerwal, Adding to your plan of attack. You really got me & neighbor thinking ! ! ! I got 4 Bathrooms & 2 water heaters, so me & neighbor are going to fill 2 tubs with scalding hot water, pull toilet off back of house & connect his ( Dewalt 45,000 BTU, MASTER BLASTER, forced air portable propane heater to the closet flange, fire up the heater & pull stoppers on both tubs at once. The hot water & propane, should really get a good conductive heat wave cranked up, and keep propane going between required tub fillings TILL THE COWS COME HOME, I think this might work. – Oily Tex Jan 31 '23 at 19:15
  • 1
    crip659, I have all ready went to city hall, they said they never started the program where they mapped the utilitys going to homes & business, but said they should have done that in hind-site – Oily Tex Jan 31 '23 at 19:22
  • Jack, last year I contacted a line finding company in Amarillo Texas (120 miles away) & they turned me down, said it would be very expensive, & besides that, they didn’t want to risk their lives coming to the Oklahoma Panhandle ! ! ! – Oily Tex Jan 31 '23 at 19:25
  • 8
    If you pump that much hot air down your sewer, I think you risk softening and collapsing your sewer lines. Bad idea. – longneck Jan 31 '23 at 20:50
  • longneck, Oops, I didn’t think about the high temperature from the (45,000 BTU PROPANE MASTER BLASTER) melting my schedule 20 PVC, sewer line, going to nix that idea for sure, good perspective on your part ! ! ! – Oily Tex Feb 01 '23 at 00:55
  • 2
    I also wouldn't fancy dropping lots of water in while trying to blow in air - in some conditions some water could end up coming out into the space heater – Chris H Feb 01 '23 at 10:00
8

I recently had a plugged PVC sewer line and had to run a 100' snake down it. I was having trouble locating the cleanout downstream. So, I sent the snake down the line and ran it with someone else in the area of where we thought it might be and could hear the snake very clearly underground. If you want to identify were the line is, I recommend renting a snake for roughly $50 and doing it this way.

asp316
  • 287
  • 3
  • 11
  • 3
    asp316: Are you saying that by dragging the snake in and out of the sewer line, you were able to hear the dragging sound resonating up through the end of the burried clean out line just below the surface. My neighbors have exposed clean outs, but if there is one in my yard, it’s burried. If this works, (providing I have a clean out), it could sure show me where to start backhoeing. Maybe wouldn’t have to wait for the next snow. – Oily Tex Feb 01 '23 at 00:21
  • 2
    @OilyTex If you can't hear where the end of the snake is, maybe you have a dog who would let you know where it is. – Andrew Morton Feb 01 '23 at 19:07
  • 1
    @OilyTex - Don't move the snake in an out, but just push the pedal to turn on the snake and let it turn in the pipe. As it turns, have someone else walk along where you think the pipe is, remembering about how far in the snake is. You'll be able to hear the tip bouncing around inside the pipe from above ground. My cleanout was buried also, but had a rough idea where it was. I used a tree feeder to push into the ground until I hit the cap. – asp316 Feb 02 '23 at 21:01
  • asp316 Yea, that makes since, slider in & rotate it so it will flop around. Should make lots more sound than pulling back & forth. Good idea. – Oily Tex Feb 03 '23 at 00:40
1

I'd be tempted to try audio. Buy a rape alarm: they're cheap, small and loud and if you lose it, it'll probably flush away. Take the connector off the end of a garden hose and attach the rape alarm to the hose securely. Set the alarm off and push the hose down the toilet. Go outside and listen - maybe use a stethoscope, they are cheap too.

emrys57
  • 111
  • 2
  • 1
    I'm not sure you'd hear it through 3 feet of dirt, but then again, someone said they could hear the snake in the line, so it's got potential... – FreeMan Feb 03 '23 at 17:51
  • FreeMan, that is reall a cool idea, & may be a (1st ever). Maybe Chris H or Ecnerwal will chim in on this. Yea, if you could maybe hear the rotating snake, then this would really worth trying. I could borrow the neighbors German Shepherd. That dog can hear everything. – Oily Tex Feb 04 '23 at 00:22