Septic tank design

[ACWxRADR]

Quick question for anyone who knows septic tanks from experience...

What is the typical or average depth of the "scum" layer atop the clarified water, and how deep does it ride in the effluent?

My dilemma regards the installation of a mechanical effluent filter at the outlet of the septic tank.

I bought an effluent filter, a brand called "PolyLok" to reduce any portion of the "scum" layer at the top or any solids from the "sludge" layer at the bottom from exiting the main solids tank and entering the bio-tank or the leach field. I bought this mechanical filter to study its design. I believe that the design is insufficient after analyzing it first hand.

The lowest level of the outflow of the effluent water pipe is only six inches below the top of the open end of the top of the tee itself. I do not think that this is sufficient headroom. I believe it should be no less than ten inches and better at maybe 12 to 14 inches. Am I wrong? Or is the scum layer thinner and riding lower than I think? I just do not want any of the fats and buoyant solids to escape over the top of the tee and escape out into my secondary treatment tank or leach field. I want to be safe with my design as it is a long term, maintenance conscience engineering aspect.

If you have sincere direction on this notion, I would appreciate hearing from you!

Gordy

 

[ACWxRADR]

By the way, to whomever is responsible for generating my "avatar" for this forum... I like it! It's really cool!
Seriously! Thank you!

Gordy

 

[Sponsor]

 

[Smooky]

Here is a link to the Nebraska septic requirements:

http://nlc1.nlc.state.ne.us/epubs/E6500/R015.0124-2005.pdf

http://deq.ne.gov/RuleAndR.nsf/xsp/...DFD3186256801006FA3D9/Body/T124Ch8Figures.pdf

http://deq.ne.gov/NDEQProg.nsf/OnWeb/Onsite

Your tank requirement are a lot different than what is required here in NC. Nine inches of freeboard are required in tanks in NC.
The best thing to do is have your tank pumped every few years depending on how many people are in the house etc. Most people say every 3-5 years. If you have a food waste disposer you may need to do it more often. I put all the food waste in a small pail and dump it in the woods. Avoid pouring grease down the sink etc.

Here are some other septic filters:
http://www.zabelzone.com/

 

[ACWxRADR]

Smooky,

Thanks!

Took me some time to read through the information, but I believe I have it resolved. The first link in the list that you supplied provided the information that I required. I was correct in my assumptions, but Nebraska code does allow greater margin of depth for the "scum" layer than I expected. The effluent filter that I bought would not be acceptable according to code, although it falls short of the requirements, it is not too far off.

According to (our) code:

The space in the tank between the liquid surface and the top of the inlet and outlet baffles shall be not less than 20 percent of the total required liquid capacity.

That is a Nebraska code, it may be different in other states. In the Nebraska code, they provide diagrams, but those diagrams do not identify the actual depth of the "scum" layer. They only cite the total liquid volume or depth as a reference for measurement and the height of the inlet and outlet baffles are calculated from this value, with consideration to other dimensions. This leaves the task of calculating the "headroom" for the scum layer up to the engineer (or me in this case).

Normally, I don't follow the of letter of the law, per se. But in cases like this, I want to do it right, not just get by. The law or the code may spell out the minimums, but I want to ensure a greater margin of security for my own conscience.

Thanks again for all the reference links Smooky, really helped me a lot!

Gordy

 

[ACWxRADR]

Oh, I should state that I am going to use the effluent filter I bought, but engineer my own receptacle for it out of standard PVC pipe so that I can set the depth as required by code. Just a little engineering and DIY project

Gordy

 

[DonL]

Oh, I should state that I am going to use the effluent filter I bought, but engineer my own receptacle for it out of standard PVC pipe so that I can set the depth as required by code. Just a little engineering and DIY project

Gordy

Don't forget the Flatulence filter, It is good to have too.

Good Luck.

 

[ACWxRADR]

Don't forget the Flatulence filter, It is good to have too.

Good Luck.

Oh, that's a very good point Don. I will order one right away. I have decided to get a "whole house" flatulence filter rather than the "point of use" style. I have never installed a point of use flatulence filter, but I have heard that they are a royal pain in the butt! Ha!

Gordy

 

[Valveman]

a point of use flatulence filter

Charcoal lined underwear!

 

[Smooky]

Zabel sells something for flatulence or other vent odors:
http://zabelstore.stores.yahoo.net/odercontrol.html