First, why is the pipe collapsing?  If the pipe is replaced will the new pipe collapse? I would look to the builder of the house (General Contractor) to fix the problem, especially if your house is still under warranty.

The first problem I see with a shared pipe would be the new pipes capacity.  Make sure that a shared pipe has the capacity to carry both lots run-off.

Good Luck

The builder of the house is no longer in business (We're the second owners).  The pipe that was used is a 3" pipe, but it appears to be made out of HDPE, not PVC or other rigid material.  I think with the freeze-thaws and a car or 2 driving on the lawn is causing the failure.

Arden

Both 3" and 4" pipe are too small to convey downspouts, personally I would go to 6" (this is the minimum I spec in design, often 8" for long runs, say over 40'/two lengths).

Go the extra expense for Schedule 80 PVC if you are planning to continue driving over it.  Freeze/thaw shouldn't affect it, as long as it is not exposed to UV rays/direct sunlight.

Make sure you get an easement around both the tank and all piping into both of your deed descriptions.  As long as there is, there should be no problem with perpetually sharing stormwater management facilities.  If there is not, a future buyer's bank will probably make you anyway.

The installation cost will be more than the material.  Using less than an 8" pipe would be false economy.  Locate the pipe where it won't be in the way of any future work such as storage buildings and landscaping.   Make sure that you and your neighbor execute easements to prevent any problems with changes in ownership.

Does this pipe drain to the road or a pond? Can you both access the outfall from your own property? If so I'd recommend two 8" pipes, one on each side of the property line. No matter what is said today and what you put on the deeds, this will haunt one of the property owners in the future. Most banks will not mortgage a property that shares any type of drainage with another.

Pipe drains into the road and we can both access from our property.

Arden

Is the HDPE Pipe a solid wall or corrugated pipe?  A solid wall pipe should not be collapsing unless the builder used a high sdr pipe (32.5 for example).  A sdr (standard dimension ratio) 17, or better yet sdr 11 should be fine for your application.

I'm not sure what specification you're referring to (I'm a packaging engineer)... It is a solid wall pipe doesn't seem to be much thicker than a large laundry detergent bottle... (I put a shovel through one of the rain gutter drains of the same material fairly easily when I was creating the flower bed in our front yard and it isn't buried below the frost line).

Arden

If Banks won't touch it, how is it that you have firstly gotten a mortgage?

Sharing of lines, while I never recommend as design standards, are a fact of life, particularly smaller towns and strata developments.  Depending on the storm runoff and the grades, 6" SDR35 should be fine for both.  THe math will have to be done first though to confirm.

With reference to future owners, you and your neighbour will have to register an agreement as a caveat against both titles indicating the shared service and a specified working area for  future repairs.  The agreement should also specify responsibility for remedial cost sharing, ie sod replacement, no permanent structures within the working allowance, etc.  If this is a strata title, the condominium or association will have to approve any agreements and covenants.

Good luck.

KRS Services
www.krs-services.com

Hi, I'm the neighbor. Just wanted to add some observations/data. The reasons for the collapse are not clear. There is evidence that it had been occurring prior to us owning the homes. The contractor who I have spoken with believes most of it occurred during construction when the properties were graded, based on numerous small "pinches" in the pipe at 3-4' intervals in the open area b/w our homes. The worst portion of collapse was near the street b/w it and the sidewalk - evidence of being driven over.

The curb on our street is about 4.5" high. Would we even be able to use a 6" or 8" pipe?

My estimates of drainage area being fed into this pipe range from 616-816 sq. ft. from my property and 695-913 sq. ft. from Arden's, depending upon whether various garage downspouts really feed into the whole system. The distance from the farthest downspout to the street is appx. 95-100'.

The contractor I have spoken with is recommending a 4" corrugated pipe. But he also is essentially recommending that I install a separate line on my own property, for the reasons as mentioned by Arden.

Thanks for your input.
Mike

Two new 4" pipe is your best bet. Rent a small 'Bobcat with a hoe attachment. the ditch won't be very deep. should be able to do the project in one day. schedule 40 PVC pipe and some glue. then a few rolls of sod

Haven't looked at the pipe size; but, if a larger pipe is needed, you could cut a section out of the curb and pave a small trianglar shaped area (level with the street) running from the curb back to the pipe outlet.  The curb around this triangular area can increase in height from the street back until it is tall enough to accept the larger pipe.  Basically a headwall type outlet.  Wouldn't be hard to construct.

Also as mentioned above, the biggest cost will probably be the installation, not the pipe.  Using two pipes will be easier on the bank and possibly your (or future homeowners) friendships.  What happens if it plugs somewhere and only affects one of you and the other one doesn't want to help with the repairs?  You will still need easements if the respective line crosses off your property.

As Dick said, you could rent a backhoe and do the work yourself.  Probably in one weekend and save some bucks.