Sewer Line Lateral Routing Design Question

[Jb9]

Hello,

I am designing a simple single family house of ~1500 sq. ft. with a basement on a small 9000 sq. ft. lot (80' wide at the street and 120' deep). The water and sewer hookup/stub is at the street on the west side of the house. I am planning on isolating my plumbing in an interior wall on the northeast corner of the house. I would prefer not to run the sewer lateral through the length of the basement in order to have a direct straight run to the sewer hookup. Are there any best practices for designing a maintenance-free or easily maintainable sewer lateral? Can I exit the basement to the north and have a run of pipe towards the west and have it gradually make the turn towards the sewer hookup/stub? The guy from the city said it's depth is 8' so I should have no problem with the grade. I am just curious if there are things to avoid (like having a sewer lateral under a driveway). Should I consider running it under the basement even? The guy from the city said that I should most likely install a pump in the basement. I know there are ao many knowledgeable folks here. Thanks again.

 

[Reach4]

Any chance of sewer backups there? If so, you want an "overhead sewer".

 

[Sponsor]

 

[Terry]

Typical grade is 1/4" per foot.
Find out where you are headed, do the math, and that's what you have to work with.
You will need cleanouts on anything with 135 degrees of horizontal change of direction.

 

[Jb9]

Thanks Reach4 for suggesting the "overhead sewer." That seems to be the prevailing design when a basement is present. I am attaching a rough schematic of where I want to put my foundation on the lot (within the setbacks I have shown). I would prefer NOT to have a main drain running the length of the ceiling in the basement and exit the front (I would like to finish the basement at some point). The options I have denoted in the drawing are what I am considering. I shouldn't have any problems making the 1/4" grade. What I am asking is whether any of the options I have drawn are clearly better than another. I will most likely have a driveway (possibly gravel) on the north side as indicated. Thanks in advance for any thoughts.

 

[Reach4]

Depending on the slope, any of those should work. You will want a cleanout outside. It seems to me that if you wanted a more durable sewer than is commonly used, schedule 40 PVC would make sense. I know that lesser piping is normally trouble-free, and I am not a pro. I also recognize that might be viewed as overkill, and maybe it would risk having the local workman gluing up an unfamiliar material. It seems to me that in the unlikely case that you later needed to dig up your sewer, restoring a gravel driveway may be easier than restoring a lawn depending on your lawn. Not so for a concrete driveway or a later room addition. It is not clear-cut to me, but I kinda like 1 or 3.

It is not uncommon to have more than one penetration outside. So you could have both options 1 and 3 joining together in the front yard if it makes routing better.

You will probably want a sealed roof-vented septic pit with a grinder pump for basement loads. That could support a toilet as well as other basement loads. I think you will also want to put in a sump for a sump pump. If your house will have a perimeter foundation drain, it will feed to that pit. That pit is usually not sealed, and its pump pumps outside usually. If that is not needed where you are, I would still put in the pit in case things change later. A sump pit with no feeder pipes can still collect water if you drill through the wall of the pit liner into the gravel layer. Putting in such a pit liner that turns out was unneeded is not that expensive. Maybe your ground water level is so low, that a seepage sump pit will not be needed.

Your water softener drain line could actually go uphill into a place where the gravity system can carry away the regeneration water rather than into the septic pit, or it could flow through the septic pit.

Your architect and local sewer department people will be able to offer some good advice. The sewer department people will probably be glad to talk to somebody who asks advice in advance, because they are usually dealing with people who have existing problems.

 

[Cacher_Chick]

Gravity is much more dependable than any kind of pumped system. Where elevation allows, I would prefer to start the lateral below the basement, so that there can be gravity drained fixtures in the basement, either now or 20 years down the road. The only time an overhead sewer is beneficial is when there is not enough grade provided to the municipal connection, and or the property is lower than most of the surrounding area, making it more subject to back up.

 

[Reach4]

Overhead sewers are beneficial if local conditions make a sewer backup worth being concerned about.

That may be compatible with what you are saying, but you seem to put the odds of a backup into a basement floor drain to be pretty low. If you are the not the lowest house, you may not flood until the lowest house takes measures to not accept water.

Overhead sewer systems do use gravity for the main floor and above. A normally open backwater valve can be useful in a basement system gravity. Flapper valves will leak. While there are systems that can do the job, it is hard to beat the overhead sewer which keeps working on the main floor even if the power is out. With a normally open backwater valve, even if it functions perfectly, your own sewage will come out the floor drains and laundry tub. While your own sewage is not so bad as the neighbor's sewage, it is still very bad.

 

[Cacher_Chick]

Reach, I am not discounting your thoughts, and you are correct in that local conditions are the greatest factor. There are millions of homes with gravity sewers and no backwater valves which have never had a sewer backup, and there are homes which have been removed because they were built where they never should have been. A comprehensive evaluation of the local conditions, including the municipal sewer system, will reflect what is best for each building site.

 

[Jb9]

Good suggestions. Who do you think would be most likely to help round out a "comprehensive evaluation?"

Should I talk to folks in the neighborhood? The city water guy (it's a small town)? Local plumbers?

I am leaning towards the overhead system with a normally open backwater valve, but I still need to perform the evaluation you describe and assess the risk of a backup.

 

[Reach4]

If you have the overhead sewer, you don't need a backwater valve. Instead there is a sealed and vented septic pit in the basement that pumps the basement sewer stuff up and into the sewer up high.

If you don't go overhead sewer and instead choose normally open backwater valve, I might come up with a system where a sewer pump pumps into the street side of the backwater valve. There are systems where there is a pit buried in the front yard that has a backwater valve with a grinder pump injecting its output. All of the sewage from the house goes into the big pit, and that will drop into the special backwater valve until the sewer backs up. Then the sewage rises in the pit. If the electric fails, the pit can store some sewage for a while. This is often done for existing houses but not new construction. http://www.expertfloodcontrol.com/products/flood_control_system.php https://www.permaseal.net/services/...solutions/sewer-backup-prevention-system.html is similar except they are using two flapper valves in series instead of a proper backwater valve. The pump pumping downstream of the flapper valves can compensate for the tendency of flapper valves to leak.

Overhead sewers are easy enough for new construction and do not rely on backwater valves.


Who to ask-- I suggest chatting with the local sewer department. Talk to the lowest houses in your area that have basements. I think basements are getting more popular in California now. They used to be pretty rare there as far as I know. Some towns have programs to contribute retrofitting mitigation projects at houses that might be prone to flooding. For new construction, I think they will give requirements and suggestions, but I doubt they would contribute financially.

But yes, local plumbers that specialize in sewer stuff would know local conditions and codes. If they are going to be involved in doing the sewer work for the house they will be more motivated I expect.

There is a modified sewer system that is similar to an overhead sewer: https://www.permaseal.net/services/...ackup-solutions/modified-overhead-sewers.html