does anyone know why you would need to use ductile iron pipe....
does anyone know why you would need to use ductile iron pipe....
(OP)
Does anyone know why you would need to use ductile iron pipe for sanitary sewer pipe where the storm is less than 2 feet at a crossing? A Town Engineer is requiring us to use dip with no transition manhole, just ferncos, to transition from pvc to dip and back again because the storm sewer is less than 2 feet away, even though the sanitary is lower than the storm.
Thx
dgi
Thx
dgi





RE: does anyone know why you would need to use ductile iron pipe....
that is pretty funny. Sounds like a well intentioned, clueless town engineer. I would hint to him that you are the design engineer and you wouldn't seal anything like that and that the town engineer will have to seal it. That usually stops them form making foolish design decisions like that.
Good luck
BobPE
RE: does anyone know why you would need to use ductile iron pipe....
Thanks Bob
dgi
RE: does anyone know why you would need to use ductile iron pipe....
RE: does anyone know why you would need to use ductile iron pipe....
While I've never heard of this requirement for storm sewer crossings, I do know that some in the industry believe that surcharing of a sanitary sewer will cause exfiltration of sanitary waste into the surrounding soil, and if the surcharge is greater than the ground water table, even push the wastewater "up" to storm sewers. Folks in New Orleans have been looking into it. It's the same reasoning as for watermain. Perhaps this town has had problems with sanitary waste showing up in the stormwater discharges, so they're being extra cautious.
We're not talking about big dollars here...you may want to reconsider how important your relationship with this town engineer is before going down the "you seal it" path.
RE: does anyone know why you would need to use ductile iron pipe....
Is the DI pipe is being requested at the crossing or does the proposed alignment of the sanitary run parallel to the storm line?
I believe I understand the town's rationale, but will reserve my opinion until my questions are answered, however I don't think that exfiltration has anything to do with it.
KRS Services
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RE: does anyone know why you would need to use ductile iron pipe....
dgi
RE: does anyone know why you would need to use ductile iron pipe....
While I haven't seen the crossing detail, I believe the engineer is concerned about the future integrity of the pvc due to the increased possibility of settlement and damage due to the weight of the storm pipe plus embankment combined with the effects of leaching stormwater (settlement or joint disruption during construction) into the surrounding soils, particularly the soils affecting the sanitary pipe. In the scheme of risk management, the more important pipe is the sanitary main, therefore, the ductile iron pipe is additional insurance due to it's increased strength.
The fernco coupler is an accepted method of transition, but I admit it might be tough to get the coupler to match the O.D. of the DI pipe relative to the SDR35.
As an alternate, you may want to ensure protection agaist settlement by providing sandbags (filled with sand/cement) to properly bridge the crossings. The 6" (vertical) crossing may be a bearcat, but it can be done. If you require a detail, I have a standard detail drawing that you could use, just change the title block. i know of some authorities that require a case bore under sensitive pipe or large diameter pipe to ensure the integrity of the pipes, as described above.
As a footnote, I have specified types of crossings such as these, and have had them recommended by engineers alike in their designs, so it is plausible that the Town Engineer and myself (or Consultants I have used) have crossed paths and shared "war" stories.
KRS Services
www.krs-services.com
RE: does anyone know why you would need to use ductile iron pipe....
RE: does anyone know why you would need to use ductile iron pipe....
dgi
RE: does anyone know why you would need to use ductile iron pipe....
BobPE
RE: does anyone know why you would need to use ductile iron pipe....
Bobpe, once again, I have to disagree with you. I have seen many design drawings and specifications (stamped and sealed by some very experienced engineers) specifying a variety of transition couplers (even Fernco couplers by name) on sanitary sewer mains, particularly replacements of pipe between manholes. In many of those cases they have been smaller diameter mains and service pipe (up to 16" I believe) and mostly clay to PVC or AC to PVC. Those couplers are also very common on sewer main and service repairs. Just ask any Public Works maintenance shop.
dicksewerrat, I guess it's never too late to learn something new, I did not realize that fernco has an adapter to D.I. Thank you for the clarification.
KRS Services
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RE: does anyone know why you would need to use ductile iron pipe....
dgi
RE: does anyone know why you would need to use ductile iron pipe....
If an engineer shows a dip to pvc (or any other material) and I will add, on new construction, as in this case, without transition manholes, that engineer does not know what they are doing. I will not go into the reasons, since we are all engineers here?
BobPE
RE: does anyone know why you would need to use ductile iron pipe....
dgi
RE: does anyone know why you would need to use ductile iron pipe....
New construction puts a different perspective on the question initially posed. Presuming the deeper main, in this case the sanitary line, would be first installation and the storm the second you should be able to effectively bridge the crossing without resorting to transitioning to D.I. at all as there really would be no need, unless there are other circimstances I am not aware of.
I am also presuming you are the design engineer for this development and/or subdivision and as such, your design is being reviewed by the Town for approval as a condition of the development agreement or subdivision servicing agreement. Getting back to your original question, yes, I believe I know why the Town Engineer requested the D.I. pipe. It's your design, if you are not in agreement with a change, it will be up to you to provide the rebuttal argument as to suitability of a transition or use of Fernco couplers, transition manholes or any other coupling system for the crossings or whether an alternate crossing option can be agreed upon. Agreement by the parties will allow the approval process to continue and the project moves forward.
Whether you agree or disagree with anyone's opinions here is really irrelevant. The threads posted to date clearly demonstrate differing opinions as to the method of transition, but ultimately, it really doesn't matter because you will ultimately choose an option you are most comfortable with. If you want manholes...use them, if you want couplers...specify them.
I personally think the whole request of transitioning from PVC to D.I. (or any other pipe type) is ridiculous and perhaps a tad inexperienced (within the context to which you have described), but nonetheless is a reality at this point. I also know what my reactions and recourse would be, as stated previously, but that is also a decision to which your firm, the Owner and the Town must resolve. I only know that my solution would not involve transitions, unless so ordered by the municipality and well documented on the drawings and in the design files and letters of correspondence.
KRS Services
www.krs-services.com
RE: does anyone know why you would need to use ductile iron pipe....
dgi
RE: does anyone know why you would need to use ductile iron pipe....
sobole@telusplanet.net
KRS Services
www.krs-services.com
RE: does anyone know why you would need to use ductile iron pipe....
RE: does anyone know why you would need to use ductile iron pipe....
I just happened upon this thread, so perhaps I'm a little late, but I wanted to point out something critical about using DIP for sewers: don't use the standard cement lining because the "nasty gasses" will eat it away, then attack the iron.
American Pipe makes a polyethylene lining for this purpose and other companies use polyurethane. I've never actually had either one installed, but I did have to spec DIP sewer once based on a client requirement, which I subsequently talked him out of.
Maybe you talk the town engineer into using a heavier wall PVC sewer or even PVC water pipe at the critical locations.
Fred