A properly designed septic system with the septic tank, pump chamber (where required), the drain field as well as the required reserve field can take up a considerable amount of real estate.
That's why the question of moving a home's septic system comes up every so often as homeowners' priorities and needs change. Often times installation of an in-ground pool may interfere with the existing drain field layout or the septic tank's location.
While it's hard to address the cost question directly without knowing the exact details and the geographical location of each project, there are some common considerations that enter into the quotations that homeowners receive from contractors. We recommend getting at least three such quotes/estimates from reputable local contractors. While many contractors can provide turn-key services, a prudent homeowner will take an active part in the project and save costs while learning a great deal about this important home system. Small but important tasks such as obtaining building permits and existing as-built drawing as well as interfacing with local health and other municipal authorities are best done by the homeowner, even if the contractor offers such services.
Perhaps the most important part in determining the cost of the septic system move project is to find out the exact location of the existing system. Drain fields can cover large areas and in some cases even spill over into the adjacent properties. This often happens when a larger property gets subdivided and an additional house gets built. In cases when the drain field extends beyond the property, the only reasonable approach would be to consider moving the septic tank but leaving the distribution box which feeds the drain field pipes alone. Canceling the project altogether in this case might be an even better approach, so it makes sense that the homeowner does this part of the job him/herself before a contractor gets involved and any money for the project change hands.
It is virtually a guarantee that a septic move project would involve moving a system that's already at least 10 or more years old. Therefore it is important to include the costs of pumping the existing septic tank before any work gets done, which can be an additional expense up to $1000. You may need to install a new tank instead of moving the old and the old one will need to be emptied and backfilled with sand and gravel so it does not settle.
If it is the drain field that will get moved, make sure you have enough of new reserve area to comply with current codes, especially is the old reserve field is where the drain field gets moved to. Consult the local Health Department to be sure that your reserve field is large enough and be prepared to hear that your property is not large enough for the new requirements.
In some cases changing the type of the septic system from gravity-fed to a pressure distribution system may decrease the space requirements and add flexibility with positioning elements of the system on the property. For example, with a mound drain field, effluent goes through a thicker filtration layer and therefore can be located in places that are closer to water table, that were not permitted before.
As you can see even from a cursory look at the septic mover project considerations, this is not a type of a project that should be taken lightly. With cost estimations ranging from $8,000 to $15,000 or more for an average 4 bedroom family home, homeowners should also be prepared to cover unexpected costs, such as bringing any part of the old system being reused in compliance with current code, or legal expenses that may arise from discovering parts of your old septic system on the neighbor's property. In some cases an alternative can be found. For example, in an earlier discussion about moving a septic system here the homeowner has found a solution in connecting to a township sewer line which was built after his house was constructed with a septic system. A municipal sewer may not be an option available to everyone but keep your eyes open, moving a septic system is exactly the kind of a home improvement project that necessitates having a Plan B.