The last time that they ran a sewer in front of our property they ran a lateral and a place to hook-up. I'm not sure that they want you cutting into their pipe, so, your #2 should be in the pipe already.

They ran ours out and dropped it straight down into the main sewer line hook-up elbow.

Definitely give your local utility a call..

These questions should best be posed to your local Municipal Sanitation Department because Municipal sewers are not governed by the Plumbing Codes but rather they fall under your Municipal Sanitation Code. While it is possible that your community makes an exception, typically the municipal sanitation providers are extremely protective of their pipes and will not permit anyone who is not in there direct employ to make any cuts or taps into the municipal sewer lines. As a rule they will provide you the exact location where the final connection will be made and the homeowner is responsible for running the house sewer from the structure to a specific point within a few feet of the final connection. Normally the municipal sewer provider will then send one of their crews to make the final connection however in some jurisdictions they do permit some commercial plumbers who have been previously certified by their agency to make the final connection. In either case, they will give you specific details on the method of cutting the tap and the type of saddle tap that you must use.

What is of greater concern to me is the fact that you state in your post that you have run a 6" line. While we often take the position that bigger is better, such is not the case with sewer lines. A 6" line is way too big and it would prove to be a maintenance nightmare in future.

All Sewer and drain lines must be sized by the anticipated load, which is calculated by the DFU (Drainage Fixture Unit) method as defined in the plumbing code.

The Plumbing Code provides us a table that lists every type of fixture than may be connected to the drainage system as well as a DFU value for each type of fixture. In order to compute the size of a house sewer we begin by listing every fixture in the structure as well as its DFU value from the table. From this we can determine the total DFU load for the whole structure.

By Example: The International Residential Code (IRC) Table 3004.1 list the following:
Kitchen sink/Disp or DWŅŅŅ..2DFU
Clothes Washer standpipeŅŅŅ.2DFU
Laundry SinkŅŅŅŅŅ.2DFU
Water Closet-greater than 1.6gpfÂÂÂ..4DFU
Water Closet-1.6gpf or lessÂÂÂÂÂ...3DFU
BidetÂÂÂÂÂÂÂÂÂÂÂÂÂÂ.. 1DFU
Shower StallÂÂÂÂÂÂÂÂÂÂÂ..2DFU
Bath/showerÂÂÂÂÂÂÂÂÂÂÂ..2DFU
LavatoryÂÂÂÂÂÂÂÂÂÂÂÂÂ1DFU
Laundry Group (Standpipe & Sink) Â. 3DFU
Bathroom Group (Lav, tub/shower/WC) 6DFU

Consider a simple 2BR/1Ba house:
Kitchen ÂÂÂÂ2DFU
Laundry Group Â3DFU
Bathroom Group..6DFU
TotalÂÂÂÂ11DFU

Now let us consider a custom 3BR / 3-1/2Ba

Kitchen
Prep SinkÂÂÂÂÂÂÂÂÂÂÂÂ..2DFU
Scullery Sink/DWÂÂÂÂÂÂÂÂÂ2DFU

Laundry GroupÂÂÂÂÂÂÂÂÂÂ...3DFU

Master Bath
Shower stallÂÂÂÂÂÂÂÂÂÂÂÂ2DFU
TubÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ.2DFU
Lavatory 1ÂÂÂÂÂÂÂÂÂÂÂÂ..1DFU
Lavatory 2ÂÂÂÂÂÂÂÂÂÂÂÂ..1DFU
Water Closet 1.6gpfÂÂÂÂÂÂÂÂÂ3DFU

Bathroom #2 (Bath Group)ÂÂÂÂÂÂ.6DFU
Bathroom #3 (Bath Group)ÂÂÂÂÂÂ.6DFU

½ Bath
LavatoryÂÂÂÂÂÂÂÂÂÂÂÂÂ...1DFU
W.C. 1.6gpfÂÂÂÂÂÂÂÂÂÂÂÂ..6DFU

Utility Sink in basementÂÂÂÂÂÂÂ.. 2DFU
TOTALÂÂÂÂÂÂÂÂÂÂÂÂÂ 37DFU

As you can see most single family residential structures would range between 11 and 37DFU
Once we have computed the total load we then refer to IRC Table 3005.4.2 to determine the correct size for the House Main Drain and House Sewer Line.

3" line with a 1/8th inch per foot pitch ÂÂÂÂ.Maximum 36DFU
3" line with a ¼ inch per foot pitchÂÂÂÂÂÂÂÂMax.42DFU
4" line with a 1/8th inch per foot pitchÂÂÂÂÂÂMax .180DFU
4" line with a ¼ inch per foot pitchÂÂÂÂÂÂÂMax 216DFU

Here you can see that the large custom home in the example above would only require a 3" line with a ¼"/ft pitch or a 4" line with a 1/8"/pitch.

From this example you could see that we could actually connect 5 large custom homes such as the one in the example above on a 4" line with ¼" per ft pitch.

The purpose of sizing the lines in the manner is to insure that at full load the line will be ½ full of liquid. This provides a sufficient amount of liquid to suspend and carry any solids such as fecal matter which might be present in the waste while still keeping the upper half of the pipe open for the free exchange of vent air.

If we were to arbitrarily install a line that is too big even at full load there would not be a sufficient level of liquid in the line to convey the solids. In this case the solids will collect on the bottom of the pipe and once the liquid has passed the solids will dry in place forming a hard lump. With each successive use the lumps will build up until the line is clogged.

Lazypup, thank you for your explanation.

In my town the sewer dept does not do connections.
They require a licenced plumber to do the tap.

The only requirement is that I do not use sharp bends (more than 45°)

As to the pipe, it will go mainly at 45° pitch (12 inch/foot)

Also from your calculations and tables one could conclude that even 4" pipe will give the troubles because even with all the fixtures used at once it will only be filled at 17% (a lot less than 50%) yet most single family houses are connected using 4" pipe and not showing any problems.

Thank you

Boggie

Originally all drain lines serving a watercloset were required to be a minimum of 4". With the advent of the water saver type waterclosets it was soon discovered that the 4" lines were continually clogging for exactly the reason stated in my previous post.

If you are just changing the watercloset a 1.6gpf may be installed on either a 3" or 4" line however for new construction all waterclosets having a 1.6gpf or less must now be connected to a 3" line.

You are correct that a vast majority of the homes in any community have a 4" line, but that is because most of those homes were built before the advent of the 1.6gpf water saver type waterclosets.

For all new construction we are not to install a 4" line unless the aggregate total DFU load of the structure exceeds 36DFU on a line with a 1/8" per foot pitch or 42DFU's on a line with a 1/4" or greater pitch.