Splicing Existing PVC Sewer Line for RV Hookup

[mijotu]

Hey Folks,

Novice here. I am installing a permanent sewer hookup for our Airstream in our backyard. The desired location for the hookup is about 10' from an existing cleanout. My question concerns the best practice for tapping the existing lines for our purposes.

The existing system is 4" PVC (or CPVC) with the cleanout terminating into a tee in the line that connects our home to the main. It seems to me that it would be better to replace the existing tee with a wye, then tap into the cleanout line for our RV access as shown in the second of the two attached images (with perhaps another wye instead of a tee in the hor>vert transition).

If you could advise as to whether I am on the right track, I will consult with you regarding appropriate ways to splice the existing line to the main (saddle, no-hub coupling, etc.)!

 

[Chris]

You got the right idea but it would be better to tap the main line than a riser. They do make a saddle wye fitting that you strap to the pipe and cut out the oval hole so you are not cutting out a section of mainline. That is the method required by most all districts where I work so I know it will be fine. We have done hundreds this way in the middle of highways. I like it better than cutting out and putting couplings as it can't settle and cause future issues.

 

[mijotu]

You got the right idea but it would be better to tap the main line than a riser. They do make a saddle wye fitting that you strap to the pipe and cut out the oval hole so you are not cutting out a section of mainline. That is the method required by most all districts where I work so I know it will be fine. We have done hundreds this way in the middle of highways. I like it better than cutting out and putting couplings as it can't settle and cause future issues.

Sounds good to me, Chris!

I had been assuming the house-to-main was also 4", but I'm guessing it must be 6" in order to accommodate a saddle. After taking another look down there, it does seems a little larger in diameter than the cleanout. Like I said: novice!

I'm attaching a couple more images, viewed from the side and main. Should I go with 90º bends, or 45s? Do the bends go deeper in the ditch? Please let me know if there are any other oversights!

 

[Chris]

45 bends, no 90's at all. It is probably 4" and they do make 4" saddles. You may have to go to a waterworks supply house and not a plumbing supply for the parts?

Install just like your first pic in t hd email last post.

 

[mijotu]

While we are on the topic, there's the issue of fume control. The grey tanks can be left open while docked to continuously empty. While there is no issue of sewer odors entering the interior through the internals, the tank exhaust is unguarded and can emit odors from the roof.

One common solution is to form a P-trap using the sewer hose fitted between the tank outlet and sewer hookup; I'm not opposed to it, but it certainly isn't an elegant solution. Another would be to install a P-trap in the sewer pipe; however, this seems a bit odd to me for reasons I can't espouse. I have also seen the WaStop, which I can't seem to find for purchase; however, it does fit that sweet spot between the other two.

Any recommendations for odor control that might fit my application?

 

[Chris]

The toilet in an rv is designed to block most odors. There is no real great way of blocking oder because the black water tank is usually right below the toilet with no ptrap. You can put a trap in ground on your clean out but it will not stop the odor.

 

[mijotu]

The toilet in an rv is designed to block most odors. There is no real great way of blocking oder because the black water tank is usually right below the toilet with no ptrap. You can put a trap in ground on your clean out but it will not stop the odor.

I agree with you regarding the black tank; however my concern is regarding sewer gasses from the cleanout/underground sewer system.

When docked, it is common practice to keep the black tank valve closed and the grey tank open to the cleanout. Gasses from the cleanout can enter the grey tank and escape from the tank vent located on the roof. These gasses can then permeate the surrounding areas, ones that we hope to enjoy!

TIA