# Sewer Pipe Reduction In Size



## WSH1852 (Mar 28, 2010)

Got myself in a bad situation with owner, engineer, architect, GC and only God knows who all else today when I refused to build a manhole where the outlet pipe was 8" and three inlets were 6", 8" and 10". The 10" line was a new line installed into an existing manhole. Plans called for me to connect the 10" to the existing manhole. The plans did not state verify size before connecting so I assumed the designer has knowledge of the existing pipe sizes. 

Manhole was in very bad condition and city inspector required it to be replaced when he checked my installation after new 10" line was installed.

City inspector talked to someone in the state plumbing board office and was told it was acceptable to make a reduction in the pipe size in the sewer line since the reduction was being made in a manhole. Never in my 40 years of experience have I heard of such. As you all know the code states, "The size of the drainage piping shall not be reduced in size in the direction of the flow." 

Have any of you ever heard of this being allowed?


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## U666A (Dec 11, 2010)

Never! Just like you stated, my Ontario code book has its own heading entitled "No reduction in size".

I wouldn't touch it with a 3M clown pole!!!


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## BROOKLYN\PLUMB (May 21, 2010)

Never heard of such a thing but you would need a concentric reducer if you did do that


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## U666A (Dec 11, 2010)

BROOKLYN\PLUMB said:


> Never heard of such a thing but you would need a concentric reducer if you did do that


Concentric to reduce?!? :blink:

I have thought of this many times, as I have ne'er seen a drainage eccentric reducer...

If (for some extinuating reason, you were forced to reduce a drain by a trade size in the direction of flow, would you not opt to use an eccentric reducer "flat on bottom"? It seems simple to me...

Any thoughts?


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## Bill (Jun 17, 2008)

Never. You can up the size but never down size.

Tell the inspector to sign off on it and its his baby when something goes wrong.


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## Mississippiplum (Sep 30, 2011)

we defintly cant have a reduction in pipe size here like that


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## revenge (Jun 30, 2011)

:blink:Let me get this straight you tied it into the man hole, cause sh.t what else can you do. After the inspector inspected it he said the man hole needed to be replaced. Then the duffas calls the plumbing board to see if your install is passible. After he stated the man hole needed to be replaced


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## WSH1852 (Mar 28, 2010)

revenge said:


> :blink:Let me get this straight you tied it into the man hole, cause sh.t what else can you do. After the inspector inspected it he said the man hole needed to be replaced. Then the duffas calls the plumbing board to see if your install is passible. After he stated the man hole needed to be replaced


No one knew the size of the outlet until the manhole was removed. GC is one of the rush rush get it done yesterday type. City inspector had already told GC manhole would in all likelyhood need to be replaced but city wanted to enter MH to inspect it before giving final word to replace. GC could not wait a day or so for city do do inspection and told ne to go ahead and make tie in. I did and all the time was telling GC we were wasting time as MH was in very bad condition. In this case I will have to stand in agreement with my city inspector up to when he allowed the reduction in pipe size.


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## Redwood (Sep 8, 2008)

Sounds like someone making work for a jetting crew... :laughing:


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## Michaelcookplum (May 1, 2011)

The only time I know this is legal is when you use a 3x4 90 to install a toilet flange


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## user4 (Jun 12, 2008)

It is allowable if you are making a transition from gravity to a force main.


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## plumberkc (Jun 23, 2011)

Bill said:


> Tell the inspector to sign off on it and its his baby when something goes wrong.


Good luck with that.:whistling2:


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## Plumb Bob (Mar 9, 2011)

WSH1852 said:


> Got myself in a bad situation with owner, engineer, architect, GC and only God knows who all else today when I refused to build a manhole where the outlet pipe was 8" and three inlets were 6", 8" and 10". The 10" line was a new line installed into an existing manhole. Plans called for me to connect the 10" to the existing manhole. The plans did not state verify size before connecting so I assumed the designer has knowledge of the existing pipe sizes.
> 
> Manhole was in very bad condition and city inspector required it to be replaced when he checked my installation after new 10" line was installed.
> 
> ...


What are the combined drainage fixture units from 6", 8" and 10" inlets?

Is the 8" pipe large enough to handle this load?

Also sounds as though you may also be over taxing the 8" outlet, the original spec called for a 10" outlet for a reason.


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## RealLivePlumber (Jun 22, 2008)

Is it privately owned? or municipal?

Anyway, are the pipes ever really going to run at full capacity?


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## WSH1852 (Mar 28, 2010)

Plumb Bob said:


> What are the combined drainage fixture units from 6", 8" and 10" inlets?
> 
> Is the 8" pipe large enough to handle this load?
> 
> Also sounds as though you may also be over taxing the 8" outlet, the original spec called for a 10" outlet for a reason.


Design engineer thought manhole outlet was an 10" line. I don't know if he was even contacted and told the line was an 8". Design engineer did tell all involved he would not approve the 10" line serving the new building to be changed to an 8". You figure this one out. I lost some additional work on this project trying to abide by the code. It is bs when inspectors allow something like this to take place when they all know it is against every code allowed in Texas. O, well as they say live and learn.


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## WSH1852 (Mar 28, 2010)

RealLivePlumber said:


> Is it privately owned? or municipal?
> 
> Anyway, are the pipes ever really going to run at full capacity?


 Private


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## Epox (Sep 19, 2010)

Bill said:


> Never. You can up the size but never down size.
> 
> Tell the inspector to sign off on it and its his baby when something goes wrong.


 A smart inspector would want the engineer / architect to sign off. I've seen that happen before. Inspectors tail can be on the line as well.


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## drs (Jun 17, 2011)

Any work outside the scope of the contract is EXTRA WORK and extra work must be paid by somebody.


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## the plumber VA (Mar 3, 2011)

Nver reduce. Stick to your guns sir


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## Mr Jay (Nov 10, 2011)

Really bad idea. Like I read in an earlier post the only time a reduction is allowed is at a 4" to 3" at a toilet sweep. Anytime other than that you're just asking for trouble.


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