Question about sewage line pitch

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dcf1999

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Hello all!

So I have a house with a septic. The sewage line going out to tank comes out of house as PVC, then transitions to clay (2’ sections for about 12’), then back to PVC. We had water that smelled like sewage in our basement. After I put a camera down pipe, I noticed the clay section is cracked up so I assume it’s leaking and draining down the soil and through basement walls (old limestone foundation).

I decided to just replace the sewage pipe so I can get rid of clay section. I dug up the sewage line and it looked pretty straight forward except i noticed the inlet to the septic is sloped up.

So pipe comes out of house on a downward grade to a wye. That wye accepts another pipe from an addition with bathroom. From that wye, pipe is level until it gets to about a foot of the tank inlet. That last foot (actually a 1/16 and 1/8 turn) is uphill. House outlet is about 1’ higher in elevation than tank inlet. Water does sit in that belly where the wye is. Distance is about 25’

So I thought of 2 situations.

1. Leave that part as is (the slight uphill by inlet) and redo the pipe from that point to house. I haven’t had any issues with stoppages for the 15 years I’ve been there.

2. After disconnected the pipe after the wye, try to rotate or raise that last section up to make it at least level, but I’m worried about breaking inlet seal at tank or the pipe.

Any other advice would be much appreciated. I attached pics.

Thanks.
 

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John Gayewski

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Pretty easy to lower the pipe. I just did it a few weeks ago. Patch it back in with hydraulic cement.
 

dcf1999

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Pretty easy to lower the pipe. I just did it a few weeks ago. Patch it back in with hydraulic cement.
the pipe appears to be sealed in the septic with, what appears to be, spray foam. I don’t know if it’s sealed better on the inside and they used spray foam as a barrier or if the whole seal is spray foam. Seems like an iffy seal if that’s the case or is that an approved way to seal the inlet pipe to the septic?

If not, I will re-seal it with hydraulic cement.
 

Jeff H Young

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the level inside the tank should be below tank inlet so it shouldnt leak or be holding a head of water. you have 7 1/4 iches of fall from the transition to clay out side house to the inlet 25 ft at 1/4 per ft is 6 1/4 inches I would typicaly have more like a foot if convieniant but you are perfect If you have 4 inch you need 1/8 minimum
 

dcf1999

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the level inside the tank should be below tank inlet so it shouldnt leak or be holding a head of water. you have 7 1/4 iches of fall from the transition to clay out side house to the inlet 25 ft at 1/4 per ft is 6 1/4 inches I would typicaly have more like a foot if convieniant but you are perfect If you have 4 inch you need 1/8 minimum
Thank you. I actually remeasured the elevation of the pvc stub out of house and where I’m going to cut it (closer to foundation) is about 4’8”. The pvc stub out of house angles down at a decent angle once it leaves foundation wall. When I measured the elevation in drawing, I didn’t have pipe dug out to foundation wall. Now I do and remeasured.

When it transitions to clay, it levels out to about 1/4 per foot. So there is a foot drop (that new elevation of 4’8” isn’t depicted on drawing) between house and tank inlet.

So I guess with all that, are you saying I should be fine with leaving the inlet pipe (that’s sloped up after wye) the way it is?

I when I disconnect it tomorrow, I will see if I can rotate it up a little. Maybe it settled over time and pushed down and I’ll be able to bring it up to level. If so, I should still have about a foot drop but should get rid of belly. I will re-measure the elevations tomorrow. I will also be putting a bed of 3/4 round rock under new pipe as a bed.

And yes, I didn’t think of that. When I pulled cover, level was below inlet.
 

dcf1999

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the level inside the tank should be below tank inlet so it shouldnt leak or be holding a head of water. you have 7 1/4 iches of fall from the transition to clay out side house to the inlet 25 ft at 1/4 per ft is 6 1/4 inches I would typicaly have more like a foot if convieniant but you are perfect If you have 4 inch you need 1/8 minimum
Thank you. I actually remeasured the elevation of the pvc stub out of house and where I’m going to cut it (closer to foundation) is about 4’8”. The pvc sub out of house angles down at a decent angle once it leaves foundation wall. When I measured the elevation in drawing, I didn’t have pipe dug out to foundation wall. Now I do and remeasured.

When it transitions to clay, it levels out to a shallower slope. So there is a foot drop (that new elevation of 4’8” isn’t depicted on drawing).

So I guess with all that, are you saying I should be fine with leaving the inlet pipe (that’s sloped up after wye) the way it is?

I when I disconnect it tomorrow, I will see if I can rotate it up a little. Maybe it settled over time and pushed down and I’ll be able to bring it up to level. If so, I should have about a foot drop. I will re-measure the elevations tomorrow. I will also be putting a bed of 3/4 round rock under new pipe as a bed.
 

dcf1999

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Sorry, I don’t know why it replayed twice or how to delete one of the double reply’s.
 

Jeff H Young

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You could cut the pipe close to the tank and put a flex coupling that way you would only have like 6 inches of back fall . generally you never ever want any but its how much work to fix and not that bad Kinda hard to actually recomend reverse fall though might say against our grain
 

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Update. I got it done yesterday. I was able to rotate the inlet pipe up and now have a downward pitch from house to septic. I just need to put some gravel under the pipe.

I piped from septic to a certain point, then piped from house to the point I stopped at from septic and connected the two pipes with a fernco fitting. However, since I’m not a plumber by trade, It took me 3 trys (wasted 2 street 22.5’s and 2 regulars 22.5’s) to get the rotating offset somewhat correct to achieve a less than 22.5 degree pipe direction change. Maybe there is an easier trick than rotating them by hand to try to find the best combination / direction to achieve the correct pitch and direction change?

Anyways, as the picture shows, I didn’t quite line them up perfect to where they meet straight on. Is that little bit of offset going to matter? There is no strain on either pipe. In hindsight, I should have just ran the pipe from house longer to meet where the pipe angles toward wye (instead of 2 meeting in middle) and it would have been easier to figure out correct orientation of the 22.5’s to make the correct offset.
 

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Reach4

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Rather than gravel, I would prefer sand. If gravel, maybe pea gravel. I am not basing my comment on experience.

I could be wrong in my choice.
 
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John Gayewski

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Rather than gravel, I would prefer sand. If gravel, maybe pea gravel. I am not basing my comment on experience.

I could be wrong in my choice.
Sand is not great. You want clean rock that can't settle. Sand is extremely (almost impossible) to compact to any kind of usable standard. Pretty much every pipe that I've removed to due to sagging and settling is bedded in sand. Sand is actually written out of our code. In Iowa you have to use clean rock or pea gravel.
 

dcf1999

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I’m planning on using washed 3/4” round rock. It takes up a little more space than pea gravel so I use less and it won’t compact.
 

dcf1999

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What about that bend in pipe though? Is that ok?

If it was something that could be seen, I’d re-do it. But since it’s buried, if it’s not an issue, I would prefer to leave as is. But want to make sure it won’t be an issue.
 

John Gayewski

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What about that bend in pipe though? Is that ok?

If it was something that could be seen, I’d re-do it. But since it’s buried, if it’s not an issue, I would prefer to leave as is. But want to make sure it won’t be an issue.
The manufacturer of that coupling will have a maximum deflection allowed for it. You'll have to find it or call them and ask.
 

Jeff H Young

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I guess there is a rock or something in the way As a plumber I think its a little rough but I dont think its an issue I think it would hold test and be fine . I wouldnt check with manufacture , I might fix it if removing the rock but its all in now I dont think that is going to leak or cause issue
 

dcf1999

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Alright…. Yea I didn’t like it either. Plus practice makes you better. Project cost a little more but looks better. Updated pics below.

Something that did help me line up the 22.5 rolling offsets… I took two 2x6 pieces of wood and put 2 screws at angles in each. That allows me to put a 22.5 on house stub, a 22.5 on a 10’ pipe and then easily slide and rotate the pipe and fittings to get the correct angles to mark. Wish I would have thought of that the other day. Anyways, getting gravel and filling trench tomorrow.

Thanks everyone for your help.
 

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Jeff H Young

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I wasent wanting you to redo it but it looks good you feel better about it but I woint bust somebodys balls over that , hand digging and trying to get it just right aint always easy It Looks good !
 
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