cleanout vs manhole? 2

[entp]

Hi,

I have a simple question re. cleanouts vs manholes. For a private campus-sided sewer system, is it OK to use cleanouts at 90 deg bends? How do you decide?

I would think at most, you could use a cleanout at every second 90 deg bend, but not at two consecutive bends. This way every branch of pipe can be accessed from a manhole at one end, and a cleanout at the other. (But obviously you would have to use a manhole if a third pipe branched off from it.)

What's your criteria?

Thanks.

 

[cvg]

my criteria is still manhole at every bend for mainline pipes. cleanouts on building connections only.

 

[bimr]

Manholes should be installed at the end of each line; at all changes in grade, size or alignment; at all sewer intersections; and at distances not greater than 400 feet for sewers 15 inches or less.

Manholes allow the use of cleaning equipment in the sewers. Cleanouts will not allow you to use cleaning equipment that is designed for manholes. Note that there has to be a bend in the cleanout. How do you expect that the cable for pulling the cleaning equipment to navigate the bend?

Cleanouts are used in buildings and perhaps in the service sewer, but not in the public gravity sewer.

 

[entp]

I guess the problem is that I've never seen the equipment used to clean a sewer and don't know how it works. What does it look like, how big is it, and how is it pulled through? (Google brings up a lot of irrelevant links, so if you know of a good one, feel free....)

I was thinking that either it could be pushed from the manhole end, or if it's dragged by a cable, a cable could be attached at both ends (if you could get the cable through the cleanout to the manhole), pulled through the pipe to the cleanout end, then pulled back through to the manhole end.

How is the cable dragged through the pipe, and what does the cleaning equipment look like?

Thanks.

 

[sam74]

If you were to have access only with a cleanout I believe you would be forced to use a plumbers snake.

http://www.hometips.com/home_probsolver/hps04/01_drains/hps_drain04.html

On public lines with manhole access you would use if available a sewer jet which is propelled by pressurised water flow. Lots of times found located on Vac trucks so after the clogged material is dislodged it can be sucked out of the line.

http://www.municipalequipment.com/sewer.html

http://www.ci.sunnyside.wa.us/services/public_works/sewer_abc/jet_rod.php

 

[bimr]

There are many different techniques for cleaning sewers.

Suppose you wanted to pull a cleaning device through the sewer on a cable. What would happen if you stood a ground level and pulled the cable up? It would drag on the sides of the sewer, especially at the 90 Degree bend at the bottom, wearing out the cable and sewer. So a cable pulley is used. The cable pulley is lowered into the sewer manhole on a hydraulic arm in order to make the 90 degree bend at the bottom of the manhole. The truck winch can then pull straight up without dragging on the sewer walls with much less torque and wear and tear on the sewer and the cleaning equipment.

Here are some articles that you can read.

http://www.epa.gov/nrmrl/pubs/600r04059/600r04059chap6.pdf

http://www.tlch2o.com/courses/WWCollection.PDF

 

[dicksewerrat]

You need to go to a few trade shows to look at cleaning equipment and or visit your local sewer maintenance dept.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[PELS]

Virtually all "public" sewer design is driven by the maintenance departments of the jurisdictional agencies. Through past experience, the maintenance people dictate what works best to avoid costly or timely fixes for sewer problems that are typicaly encountered and also what kind of design eliminates or minimizes the frequency of maintenance problems. Primarily we're talking about eliminating obstructions in the line that prevent or hinder the performance of the system. Obstructions would tend to occur more often in a 90* bend as opposed to a lesser angle.

You stated this would be a "private" sewer system. The suggestion is that the system will not be maintained by a public agency but by a private owner; therefore, you are not bound by agency design standards but rather by your opinion as the design professional as to whether or not using cleanouts in the manner you described is feasible.

Some factors to consider in a scenario such as yours:

1. Quantity and frequency of the design flows.
2. Diameter of the sewerline (probably 4" to 6").
3. Type of users generating the flows for the system.
4. Length and depth of the sewerline prior to discharge to a public system.
5. The number of 90* bends (15-20 versus 3 or 4).
6. The distances between bends.
7. The willingness of the owner to understand the maintenance responsibility that goes with this concept.
8. The value engineering analysis of construction cost savings versus maintenance costs over a specified period of time.
9. The ability to get your plans approved and a building permit issued with this design.

I'm sure there are a few other factors that come into play but those are the first that come to mind. I would also try to research existing sites that have used this design concept and obtain performance and maintenance data. I have seen the concept used in private systems around here so you are not alone.

 

[CivEnvEng98]

I'll give my $0.02 in cleanouts & bends...

With sewer laterals/services (i.e., 6" and smaller) I do not design 90-bends. I use two consecutive 45-degree bends. Some Utilities won't allow 90-degree bends anyway and they also require a cleanout extended behind each bend, some leave that up to the EOR to place them where and how many is needed. I always add a cleanout at every bend, and work with the architect to give me the best possible building cleanout location so I can minimize the number of bends. Most of the time the architect can only do so much and it's up to the civil engineer to maximize sewer layout outside the building.

Also I put cleanouts on laterals at 75 foot intervals on straight runs.

Next issue I end up dealing with is how long of a sewer lateral before I end up with a Manhole/Main system (i.e., 8" or greater). Some Utilities, including the one I used to work for won't allow sewer services/laterals 6" and under greater than 150 feet in total length. This is because of the following "Ten States Standards" statement, which about every US utility uses as part of their technical guidance:

Chapter 30 Design of Sewers
Section 34 Manholes
part 34.1 Location

states: " .....Cleanouts may be used only for special conditions and shall not be substituted for manholes nor installed at the end of laterals greater than 150 feet in length"

So after 150 feet I end up having to install a Manhole/Main system. With this system I typically design angles no less than 90-degrees and place manholes no further than 400 feet from manhole centerline to manhole centerline.

Good luck!

 

[jgailla]

entp,
Even if this is a private system, the jurisdiction in my area (Florida) won't accept cleanouts instead of manholes. Florida (FDEP) specifically references Ten States into the administrative code. Ten States has an out for using cleanouts in 34.1. "Clean outs may be used only for special conditions and shall not be substituted for manholes nor installed at the end of laterals greater than 150 feet in length." We had a "special case" recently where we had to go in between two tunnels (existing MEP and proposed pedestrian) and a manhole simply wouldn't fit. The lateral was less than 150 feet long. We had a manhole, 45 with cleanout, another 45 with cleanout at the other end, and manhole. The DEP asked us to remove the cleanouts anyway, but backed off when we had a good reason.

 

[cvg]

it is not uncommon for some private systems to be taken over by the public agency. This happens quite regularly with homeowners associations which defer maintenance and do not establish a significant reserve or maintenance fund to pay for it. homeowners may then complain directly to the city to come in and take over the system and the city inherits a substandard system. to avoid this, some cities require higher standards for private systems.

 

[dicksewerrat]

Some times the local gov't says upgrade or we don't want it.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com