Author Topic: Sewer line drop  (Read 10027 times)

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Offline Brigit-Carol

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Sewer line drop
« on: January 20, 2005, 05:12:14 AM »
Wow!  I've been away for six months and come back to find my favourite discussion list has gone high class.  I like the new format.

I'm finally ready to begin building a small cabin based on John's plans.  It will be around 75' from the septic tank.  Since I'd dearly like a flush toilet, I'm needing to know what rate of drop is needed for the solids to flush through the line.  Does anyone know or can you refer me to a web page?  I've done a search and come up empty.

Many thanks,  Brigit-Carol

Offline John Raabe

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Re: Sewer line drop
« Reply #1 on: January 20, 2005, 10:12:54 AM »
The magic number is a shallow 1/4" to the foot, lower than most people expect. Steeper than that and the water runs away from the solids.

In my area the black water sewer line needs to be as short as possible. We try to get the septic tank within 6' to 8' of the house. The drain field can be further away and at a different slope as the effluent lines are not as subject to clogging up.

See if you can't locate the tank closer to the house. It will be much easier getting the right slope on the sewer line.
« Last Edit: January 20, 2005, 10:13:46 AM by jraabe »
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Offline JRR

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Re: Sewer line drop
« Reply #2 on: January 20, 2005, 02:22:32 PM »
John is right, the outside drain lines need to be at the same slope as drains inside the house.  I always try  for 3/16" per foot.   Anything much more or less leads to problems.   However, when needed, a vertical drop is not a problem if vented properly ... usually a pipe that is the right diameter for the flow will "self vent".

Offline Brigit-Carol

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Re: Sewer line drop
« Reply #3 on: January 20, 2005, 04:04:33 PM »
Many thanks!  

Offline JeffnTN

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Re: Sewer line drop
« Reply #4 on: January 21, 2005, 05:08:38 PM »
Yep.  1/4 of one inch is the magic number,


Septics are pretty easy.... if you do not mind digging...  

I used to build 1 million gallon concrete tanks for water/sewer plants....  

But that is another story..


Jeff Moss

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Re: Sewer line drop
« Reply #5 on: February 14, 2005, 07:54:50 PM »
I was looking at this post and I think I might have a problem. I had a septic system installed on a piece of property that I want to build on in the future and the tank is about 100' from where the exit of the sewage pipe will be from the house. I didn't realize that the 3/16" to 1/4" per foot was that critical and the installer never mentioned it. I guess the tank could be dug up and moved if needed. If I could reach that majic number of 1/4" fall per foot how far can the line from the house be without having blockage problems. Are there pumps available to pump sludge to the tank. Please comment because Im not sure what to do.

Mossie

Offline glenn kangiser

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Re: Sewer line drop
« Reply #6 on: February 14, 2005, 08:48:05 PM »
How deep is the opening below ground - is it  on a down hill slope from house to tank that may help?  You can bring your pipe up above 12"  of cover if you use materials that are legal within the walls such  as regular abs (as opposed to psp).   Note I am going from code as I remember from years ago.  It won't do any good to raise it to near ground level if under a slab floor where you need the depth for proper flow.  You could also raise the house pad or floor elevation some to help with the slope if you don't want to dig up the tank - depends on which problem is the worst.

Slope should work if kept at 3/16 to 1/4 per foot for 3" pipe.  As I remember you could go down to 1/8 per foot if you went up to 4" pipe.  Someone please correct me if I'm wrong - various city design information seems to agree with me -showed 1.05 feet of fall per 100 feet in one place with a 4 inch line - another place agreed.- Glenn
« Last Edit: February 14, 2005, 08:52:16 PM by glenn-k »
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Offline JRR

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Re: Sewer line drop
« Reply #7 on: February 15, 2005, 12:47:12 AM »
Jeff
I'm not sure if you think your tank may be too deep or too shallow.

I'm no expert, but the following is what this old novice "thinks" (... not "knows").

"Too deep" is never a problem... because you just install a combination of vertical drops and properly sloped horizontal runs to get to the tank.  Each vertical drop is usually a good location for a "clean out fitting" to be installed.  Never glue the cap of a clean out in place... you want it to be easily removable.  Use Vasoline as a cap sealant/lubricant to help prevent the intrusion of roots and make the cap removable.

"Too shallow" can be a bit of a problem.  But sewage basins and pumps are available as packaged units and many houses use them.  Some multi-floor houses have a combination.... the upper floors have regular gravity flow... the lower floor or basement have a sewage pump that pumps "up and over" into the gravity sewer line.  I would prefer to install this pump outside the house ... but they are often installed in basements.

A properly sloped horizontal (smooth bore) pipe run can work for any length... though local code may limit the length.   It is prudent to install "clean-outs" at some minimun spacing... local code may dictate a spacing.   I personally like many clean-outs and vents... every 20 - 30 ft.   Their locations (and the rest of the septic system) should be part of the "as-built" land lot drawing.  Open-ditch photos are good to keep.

Offline mossie

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Re: Sewer line drop
« Reply #8 on: February 15, 2005, 01:29:27 AM »
The tank is not deep enough. It had to be that way as per the sewage inforcement officer. I will need to have the installer come back when I get framed up. If we have to move it closer oh well; live and learn. In my area there is no city sewage and leech beds are real hard to get approved. I got lucky when we found the area that passed so I will work with what I have. Should not be that much of a problem to move it as long as we can get it back out without damaging it.  Thanks; I will post when I find out more. Maybe someone else will learn from my mistake.  Mossie
« Last Edit: February 15, 2005, 01:30:49 AM by mossie »
Mossie

Offline JRR

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Re: Sewer line drop
« Reply #9 on: February 15, 2005, 03:47:14 AM »
The tank depth and location has to suit the leaching field; so be sure any changes you make can/will be approved.

Don't be afraid of the concept of a sewage basin/pump.  I've actually designed custom ones for industrial/manufacturing sites.  I prefer to use a self-priming pump that can be installed above-ground... as opposed to a submerged pump.  Always included a "hi-level" alarm to help prevent overflows.  Since these were rather large facilities, dual pumps were always installed... to help manage maintenance actions.  I use to specify Gorman Rupp centrifugal T-series sewage pumps (http://www.gormanrupp.com/) .. a little pricey for home use... but Northern Tool carries a similar one.

I'm sure there are small standard home sewage pumps, complete with basins, avail at Home Depot and the like.  Not too expensive to buy or operate.  Probably lower cost than moving a septic tank.
« Last Edit: February 15, 2005, 01:09:01 PM by JRR »

Offline glenn kangiser

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Re: Sewer line drop
« Reply #10 on: May 02, 2005, 07:53:38 PM »
Thanks for posting this JRR, I hadn't seen it earlier.  I just finished digging a 6 foot deep x 60' long leach field on the side of a rather steep hill- got approval today to put in the rock for a customer/friend.  We have to put in a pump and basin as the only place we could put the leach field was up 24' elevation - 130 ft run.  Now to find an affordable pump.  My first time for other than a normal leach field or infiltrators-- I guess this means I'm not a virgin anymore ???
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Offline JRR

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Re: Sewer line drop
« Reply #11 on: May 03, 2005, 04:40:46 AM »
glenn
I would suggest you install conventional gravity drain to an outside "pumping station".    Then if the homeowner doesn't stay on top of his pump maintenance, a small spill won't be so bad.  Check out the little motor-pump unit sold by Northern Tool.   I think it is made by Gormann-Rupp but relabelled.

The big-box home improvement stores also sell similar units ... some complete with basin.
« Last Edit: May 03, 2005, 04:42:38 AM by JRR »

Offline glenn kangiser

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Re: Sewer line drop
« Reply #12 on: May 03, 2005, 05:35:57 AM »
We have gravity to the tank then will have a 200+ capacity vault tank to put the pump in.

Are you saying we should add a conventional gravity leach field to the high water point of the vault?  
If that is it we would have to add it after inspection.  There is room for a leach field at the bottom but there is seasonal ground water about 3 feet below the ground surface  in winter with fairly heavy clay 2 feet below surface

We have 24 feet of elevation rise so have to go with a little heavier pump and warning buzzer and light also.  ZOELLER is one that posts specs on the net but a bit more expensive - I'm still checking prices for my friends.  Thanks for any advice JRR.
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Offline Daddymem

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Re: Sewer line drop
« Reply #13 on: May 03, 2005, 05:59:38 AM »
Hey! I can be relevant in this forum!  

Pipe slope: yes 1/4" per foot (2%) is my usual target, but 1/8" per foot (1%) can be done.

Cover over system components:  1-3 feet is the goal.  1-foot for protection of the tanks, etc.  3-foot to keep oxygen in the system for the break down of ammonia.  In simple terms, there are two important bug types in septic systems; aerobic organisms (breathe oxygen) and anaerobic organisms (don't breath oxygen).  Each type of bug does its own thing best, so you need both to fully break down effluent, too deep and you lose the first step of the nitrogen process.

Pumping effluent:  There are many packaged systems available, Myers puts out a decent one, e-one puts out an expensive one (but this is a tank that will last and last).  These units come fully set up to go, basins, control panels, alarms and all.  There are two types of pumping.  The first is pressure dosing which involves squirting the effluent evenly across a leaching area with pressure (this takes considerable design).  The other involves gravity dosing which is simply lifting the effluent higher to a d-box where it flows into the leaching area by gravity.  If you pump to a leaching area, put a tee or splash plate on the d-box and check that you don't overdose the d-box before you bury it, it is common that you need to seal the cover.  Remember that every time that pump turns on, it uses energy so avoid pumping whenever you can.

If you have a well and septic on the same lot, or if you are near surface water or wetlands, or if groundwater is close to the surface, do us all a favor and install an effluent tee filter on your septic tank.  They aren't too expensive, and with regular (easy) maintenance they really help break down effluent.  Zabel is one source: (they also sell a bunch of cool septic components and pump systems)http://www.zabelzone.com/wastewaterfilters.htm

I cringe when I hear about areas that don't have decent septic regulations and allow any Joe with a shovel to install some pipe in a trench and call it a leaching area (this isn't to say that nobody but engineers or installers can do this work, but someone with some valid experience should be doing the work).  It is sooooo easy to destroy our drinking water supply with inadequate sewage treatment.  Nitrogen is quite nasty and can even be fatal in babies.  

Our State regulates septic systems and provides some decent rules:  
*100-foot separation from drinking water wells to leaching area (effluent plumes can easily go 50 feet or more from a leaching area given the right circumstances)

*4 foot separation from the bottom of leaching areas to seasonal high groundwater (5-foot in rapid percolation areas) to provide enough time for effluent breakdown prior to reaching the groundwater

*50-feet leaching area to wetland setback (let's keep those critter habitats clean)

I'll get off my soapbox now, I hope I got this stuff in understandable terms (us engineers sometimes talk funny, BOD, TkN, TSS and whatnot).  If you want a decent set of rules to follow check out our state regulations: http://www.mass.gov/dep/brp/files/310cmr15.pdf
These are very strict, but we have seen improvements in water quality since implementation of these regulations.

Remember: I only play an engineer at work so take this all as opinion only  ;)
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Offline Daddymem

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Re: Sewer line drop
« Reply #14 on: May 03, 2005, 06:04:20 AM »
Glenn, If you want I can send you a tool I use for pump systems.  It is an excel spreadsheet that will allow you to create a system head curve that pump guys would understand.
I have heard of Zoeller and they are usually mentioned when economics come into play.
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Offline glenn kangiser

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Re: Sewer line drop
« Reply #15 on: May 03, 2005, 06:07:27 AM »
Thanks a ton, Daddymem - I really appreciate it.  Will have to print it out and read it on the way up the hill.  I fell a couple of old growth trees - 120 to 140 feet- for a new house  - have to go bury the spotted owls, squirrels etc. and their nests and remove the logs.  I'm originally from Oregon.  We had a saying there.  "I like spotted owls.  Fried."

Thanks again.
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Offline Daddymem

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Re: Sewer line drop
« Reply #16 on: May 03, 2005, 06:09:04 AM »
Heh, if were only that light of a read.  I have been doing this for 7 years now and I still get confused by some of the stuff in there  ;D
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Offline glenn kangiser

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Re: Sewer line drop
« Reply #17 on: May 03, 2005, 06:09:44 AM »
That would be great Daddymem.  I have Excel - do I have brains to use it ???

Thanks
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Offline Daddymem

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Re: Sewer line drop
« Reply #18 on: May 03, 2005, 06:16:51 AM »
Email sent.  Good luck.  I forgot to mention above, if you put a tank in the water table, make sure it won't float!  Look up bouyancy calculations on the web, it is a really easy one to do and it saves a bunch, floating tanks suck!
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Offline glenn kangiser

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Re: Sewer line drop
« Reply #19 on: May 03, 2005, 06:21:20 AM »
I remembered that could happen and think I'm safe. I left the customer standing on it to hold it down. ;D

Actually its in a bit drier area and more well drained.  Thanks again for the help.  Will check the spreadsheet tonight.
« Last Edit: May 03, 2005, 06:21:39 AM by glenn-k »
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Offline JRR

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Re: Sewer line drop
« Reply #20 on: May 03, 2005, 10:42:41 AM »
Daddymem touched on one point that I want to reinforce:  It's important not to "pump through" the septic tank.  

Set the level switches on the pump so that small volumes are pumped in each pumping cycle ... volumes that are the same as one or two toilet flushings.  The reasoning is to avoid pushing matter (that the anaerobic's haven't yet treated) into the leaching field.

Yes, this makes the pump work more often .... but makes the septic system last longer.

And when selecting the pump, ... get the "head" required to overcome the elevation, but after that need is met ... the "slower, the better".


Oh, and earlier I was not suggesting a second leaching field.... just suggesting that the pump and basin should never be indoors unless it can't be avoided.
« Last Edit: May 03, 2005, 10:49:45 AM by JRR »

Offline Daddymem

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Re: Sewer line drop
« Reply #21 on: May 03, 2005, 11:09:16 AM »
Around here we can only pump 25% of the flow to the septic tank.  We usually try to pump to a manhole or pipe upstream of the tank so the flow has a chance to "calm down" a bit and not stir up the tank sludge and scum.  With an effluent tee filter, it isn't as much of a concern (though you are still stuck with the regulation here).  If we are talking simply about trying to get a shower or toilet to the septic system, there is an even easier solution that is similar to the Quik Jon system here: http://www.plumbingsupply.com/sewage.html

I have seen a version where it is like a small wastebasket tilted sideways.  The shower or toilet is raised off the floor to flow to it, and it just runs as water is sent to it.  It is usually pumped up to the pipe going through the foundation wall to the septic tank.
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Offline glenn kangiser

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Re: Sewer line drop
« Reply #22 on: May 03, 2005, 01:08:42 PM »
Break from logging for a few minutes- got the first load in.  Daddymem- looks like I will have to study a little longer then maybe I'll learn enough to be dangerous -  :-/

JRR - the tank is about 30 feet from the house and the vault and pump will be next to the tank - gravity house to tank then pumped from vault to drain field 24' elev up.  Thanks for the info about slow pumping -now I have a better idea what I'm looking for in pump size.

I appreciate all the tips from everyone.
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Offline Daddymem

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Re: Sewer line drop
« Reply #23 on: May 03, 2005, 02:50:36 PM »
Whoo boy.  Just got off my soapbox and looky what I found:
http://story.news.yahoo.com/news?tmpl=story&cid=387&e=1&u=/ibsys/20050430/lo_wews/2694191

Warning! Not for reading while you have food in front of you!
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Offline glenn kangiser

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Re: Sewer line drop
« Reply #24 on: May 03, 2005, 06:14:36 PM »
I read that last night on the DailyRotten.  I drilled water wells for ten years and am having a hard time figuring out how that happened unless a whole bunch of people didn't do their jobs right.  Where was the well seal, and the separation and other safeguards ???  Anybody for a nice fresh glass of lemonade?
« Last Edit: May 03, 2005, 06:15:42 PM by glenn-k »
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