Alexcmia, It appears that the tee into the riser was installed too low and the p-trap was shortened to remain above the ceiling tile (For starters) The blower is probably sucking air thru the trap because it is not deep enough. A second problem is, why is there sewer gas in a condensate line? check the termination point of the riser, it should be an indirect connection to the sanitary sewer. It is probably direct connected and causing gases to be sucked up into the blower. An HVAC guy could probably solve the problem quickly. Take Care Dan Martyn

You are absolutely correct, Generally the excavation is the difficult & expensive part of your repair, but you seem to have that under control. Now as we discuss the plumbing part of the job allow me to give you the correct trade nomenclature so you will be on the same page with your plumbing suppliers and inspector. Technically speaking, what you are working on is not a drain line, it is the "House Sewer" line. Code requires a main cleanout within 3ft of the point where the house sewer enters the structure. In the case of slab construction it would be found outside and approximately 3' from the foundation. For houses with a basement the main cleanout is generally just inside the footer wall and for houses with a crawlspace it can be inside or outside the footer wall. The line from the main cleanout to the septic tank or municipal main is defined as the house sewer while the main line inside the house is defined as the "House Main Drain". This is important to know because the codes allow different materials for each type of line. The raw cut end of a pipe that has no threads or fittings is called a "Spigot end" or simply a "Spigot" The formed female end of your pipe is called an "End Bell" and pipe which has an end bell on one end and a spigot end on the other end is called "Hub & Spigot" pipe so that glazed clay pipe that you have is "Vitrified clay hub & spigot pipe". It was generally made in 4' sections and when laid, the hub is always placed on the upstream end. While it can be done, as a general rule it is nearly impossible to cut that type of pipe without breaking it. (I have made & attached an illustration to help you understand the text.) To begin your project excavate until you find the end bell on a section of pipe downstream from where you want to install your cleanout. Fernco makes a rubber donute gasket that will fit inside the hub of that clay pipe, then your PVC will be inserted into the center of the Fernco. (make sure the Fernco you buy is listed as "Vitrified clay x PVC") If you can not find the correct Fernco some jurisdictions will allow you to pack the joint with "Oakum" which is a fiberous rope looking material that is impregnated with tar. To install the oakum you wrap it around the pipe and push it into the joint with a broad screwdriver, packing as tight as you can. You can make your cleanout with a Wye & 1/8th bend (sanitary 45deg elbow) in the manner you describe, but what you are making is a running cleanout and in some jurisdictions they require a running cleanout to be installed to the line can be snaked in both directions. The preferred fitting is a "Rodding Tee" sometimes called a "Cleanout Tee". An ordinary sanitary tee has a radius towards the downstream direction of flow, but a Rodding Tee has a radius in both directions. In some jurisdictions if they require a bi-directional cleanout and if you use the Wye & 1/8th bend method you actually have to make two cleanouts, one in each direction. Also not that the one for snaking in the upstream direction must be installed on the downstream side of the downstream cleanout. That is to insure that you can snake the complete line. If they were reversed you could not snake the space between the two cleanouts. You then continue your new PVC pipe to the Spigot end of the vitrified clay pipe on the upstream side of your repair and connect the PVC to the clay pipe with a Fernco coupling. (Careful here. Although both the clay pipe & the PVC are 4", that is the ID of the pipes, but because the clay pipe wall is much thicker than the PVC pipe a common 4" Fernco won't fit. Make sure you get a Fernco coupling that is listed as 4"PVC x 4" Vitrified Clay. (Although I have on occassion found them in Home Depot & Lowes as a rule you will probably have to go to a real Plumbing supply house to find the correct Fernco's) Now to answer your next question, how to cut the PVC. You can easily cut PVC with a hacksaw, a PVC saw or what I prefer for cutting 3" and larger, a common hand wood saw. Here is a tip when cutting pipe with a saw. After you start your cut, when you are about 1/4 of the way through the pipe, rotate the pipe a 1/4 turn, cut down another 1/4, then rotate the pipe again and finish your cut. Rotating the pipe in that manner will help keep a straight cut line on the end of your pipe. Sand is the preferred material for bedding the pipe and continue covering with sand until you have a minimum of 4" on top of the pipe, then you may use "Clean fill dirt" that is free of rocks until you have 12" above the pipe. When you finish backfilling it is best to have the top about 3" or 4" above grade to allow for settling. One a side note, the first clay pipe you found was 4" clay tile that was just laid end to end with no seals around the pipe, then it was covered with pea gravel. Back in the days before perforated poly or PVC they used that method to make leach fields or to install storm drains. The little gaps between the sections allowed the water in the pipe to leach into the soil the same way that modern perf pipe does.

Normally when connecting single family residential structures to a municipal sewer system they require each structure to have a separate line, however you stated that both your contractor and the town have suggested combining the lines so it goes without saying that you will be granted an exception to the individual line rule. The question then becomes, Can the single 4" line adequately handle the load of all three structures? It is impossible to give an exact answer because you did not mention where you live and without that information we cannot determine if you are under the IRC(International Residential Code) or the UPC(Uniform Plumbing code"). When designing a DWV(Drain,Waste & Vent) system we begin by listing all the fixtures in the structure that will ultimately be connected to the drainage system. We then refer to a table in the code that assigns a DFU (Drainage Fixture Unit) load value to each fixture. In addition, for some fixtures the code assigns a minimum line size. I.E. a shower or laundry standpipe is required a 2"line and a water closet is required a 3" line. At any given point within the structure where two or more lines connect we must compute the DFU load at that point and insure the line downstream from that point is large enough to handle the total combined DFU load. Te determine the size of the "Main Drain" and "House Sewer" we compute the total DFU load for the entire structure then consult another table that lists a maximum number of DFU's that is permitted based upon size the pitch and size of the line. To provide an example I have worked up your problem based upon the IRC tables. (Even though the actual DFU values and line load maximums are slightly different in the UPC, the end result would be approximately the same.) Obviously we would need to know exactly what fixture are installed in each structure but for the purpose of illustration we sill assume each bathroom to be a standard bathroom group, Lavatory, Tub/shower & a 1.6gpf Water Closet. Lavatory............... 1DFU Tub/shwr............... 2DFU Water Closet(1.6gpf)...3 DFU Bathroom Group total = 6DFU's Four bathrooms = (4 x 6DFU's) = 24DFU's Kitchen Sink with Dishwasher....2DFU's Laundry Standpipe.............. 2DFU's Total per structure equals ... 28DFU's The existing load on the 4" sewer line is two structures so the existing load is 28DFU's x 2= 56DFU's. If we then add your structure the new combined load would be 28DFU's x 3 = 84DFU's. A 4" House Sewer with a 1/8" per foot pitch is rated for a maximum of 180DFU's and if the line has a 1/4" per foot pitch the maximum is 216DFU's therefore even with your house tied in, you will still be less than 1/2 the maximum allowable load for a 4" line. Now in regards to access for maintenance and the respective cost to each homeowner. Normally the municipal sewer provider is responsible for maintaining the last 3 to 4' and the tap into the municipal sewer line. Each homeowner is then responsible for all remaining line to the structure. In the case of a shared line such as you suggest there should be a contractural aggeement between all parties that the shared portion of the line should be treated as a common main and the maintenance cost should be equally shared by all three homeowners. Each respective homeowner should then be responsible for the maintenance cost of the line from their structure to the tie in point on the shared line. The contract should provide each respective homeowner an easement to allow access for maintenance of their line to the tie in point on the condition that they will be responsible for both the cost of the maintenance and any landscape that is disturbed during the maintenance process.

The pipe is made of concrete apparently. It's hard to tell whether the cracks go all the way through. They don't look that deep, maybe more on the surface, but that's pretty much the gist of the problem -- by the time you dig it up to diagnose it, you may as well replace it. If they are minor surface cracks, and there is no root invasion, then it seems like we should just keep an eye on it (annual scoping) to see if it gets worse. Does that seem like a common sense plan?