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Insulating PVC sewer pipe that has to be laid shallow


Richard904's Avatar
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05-24-05, 04:30 PM   #1  
Insulating PVC sewer pipe that has to be laid shallow

In our town (NW Boston suburb) sewer pipe (now six inch diameter PVC) should be laid four feet or more below grade. Due to conditions such as a nearby neighborhood gas line and some ledge some of the line has to be laid shallow. Is there not insulation that can be put around the pipe that can act equivalent to so many feet of dirt that would thus compensate for the lack of depth? We are actually also building a terrace that would hopefully add further effective depth to the pipe.

 
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05-25-05, 08:01 AM   #2  
First and foremost you have to check with your local building department to ascertain what is permissible. You will also find out that they will have the most practical solution for you.

Insulation is not a practical solution because insulation retards heat flow, which explicitly implies there must be a heat source. Pipes four feet below grade have the earth as a heat source.

 
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05-25-05, 07:18 PM   #3  
Using rigid foam above the PVC pipe

If we lay rigid foam insulation over the sewer pipe, then would this not act as a barrier to heat loss from the pipe and below to the colder soil above? This would have the effect of apparent added soil depth. Other than the heat of the earth there is the flow of warm waste water and whatever the ambient temperature is in the town sewer pipes that gets back to our pipe.

 
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05-26-05, 05:32 AM   #4  
Heat Load is the term used to determine the amount of heat requires to compensate for the amount of heat loss per hour. While it is true that some heat maybe retained from the earth with the insulation installed above the pipe, from the sun during the day, from the city main sewer pipe and from the waste produced from your house; it will probably not be sufficient. Especially in the middle of the night when you and most other people are sleeping and the sun is not present. Compound that with the fact that the Heat Loss is at its greatest at that time.

The other thing to consider here is that if your application does not meet city code, it will eventually come back and bite you. Even if you sell the home 10 years from now and the new homeowner finds out you improperly installed this waste line. They certainly have recourse.

Again, I strongly recommend you check with your local building department to ascertain what is permissible. You will also find out that they will have the most practical solution for you.

 
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05-27-05, 11:28 AM   #5  
Pat S
First - what you propose is not to code, not to mention that you have to be licensed and permitted (read - no DIY) to do any work on sewer lines in MA.

Second - the 48" depth is also to locate the sewer/water line below where frost heaves will occur. No amount of insulation is going to protect that pipe from breaking/splitting/leaking etc if the ground freezes and then heaves when it thaws.

Third - I suspect you have done other DIY work without the permits (like adding a bath in the basement?) ,and this is why you are looking to do this sewer line DIY. I can sympathize, especially with the higher sewer fees and property taxes you'll pay with that extra bathroom (read - higher assessment) - but sewer work is a public health issue also.

Fourth - If there is a buried gas line in your area, you are required to call 1-800-DIG-Safe before any excavating. I'm not trying to be a rules and regs hard*ss - but these rules, regs, codes, and laws are there first and foremost for safety. In this particular scenario - you are better off biting the bullet and doing this following the book. I can almost guarantee that if you don't, someone will report you and then it may all come crashing down around you. No joke - I've seen it happen.

Fifth - Did you know if something goes wrong with anything related or indirectly related to any DIY work that requires an inspection - your homeowner's insurance won't cover it and may even be cancelled? Think that over while you are looking to bypass safety concerns to save a buck.

 
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