Manhole tolerance 1

[gusongjun]

Hi,

Regarding manhole installation, does anybody know the tolerance?

Thanks a lot!

 

[cvg]

tolerance for what?

 

[gusongjun]

Tolerance for offset.

 

[Ryb01]

Still unclear about what your asking.....

However, if your speaking about pipe inverts.....general rule of thumb is 1m max between inverts. If invert separation needs to be greater than 1m, use a drop structure. Also contact your local governing agency, they might have specific requirements.

If your speaking specifically to the installation during construction, typically the pipe opening's in manhole are quite larger than required, contact your manhole manufacturer for specific details. A permanent seal is then formed between the manhole and pipe by either a gasket or concrete parging.

Hope this helps.

Ryb01

 

[gusongjun]

Sorry.

I might confuse you.

For the tolerance, I mean as-built coordinates/elevation is not same designed coordinates/elevation. So the tolerance for this difference.

Many thanks for your kind concern.

Best regards,

 

[cvg]

you mean the sewer invert is not as shown on plans? A tenth of a foot might be acceptable. But really depends on the slope of the sewer. And what about the rest of the sewer (between the manholes), is is built per plans? Survey the elevations and re-run your hydraulic analysis if you are unsure. As far as horizontal, is it in the right of way or easement?

 

[gusongjun]

To cvg:

Thank you!

I don't mean tolerance of pipe invert grad and line.

I want to what the tolerance for concrete manhole. I heard that tolerate for elevation is <=10 mm, elevation is <=10 mm as well.

 

[cvg]

apparently, I am still unclear what the problem is

 

[rowingengineer]

Bo you mean diameter or thickness of manhole, ie the structure, then this should be in accordance with your structural code.

When in doubt, just take the next small step.

 

[Ryb01]

Still unclear about what your asking but if "I don't mean tolerance of pipe invert grad and line.", then there isn't really a specific tolerance. If your pipe inverts and grade are ok, the manhole can be adjusted to finished grade or other wise with spacers or with modulock spacers. Seems like a minor detail not worth worrying about if your pipes are ok.

 

[Hoagie]

Do you mean construction tolerances? If so, then it all depends. When the contract doesn't define what each should be, I usually hold to USACE tolerances.