Do-It-Yourself Septic Plans


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Septic Systems for Churches-Theaters



The following article applies to the drawing template package sold here from 

 The drawing templates are in both standard PDF and CAD (What is a CAD Drawing?) These drawings will enable you to prepare a set of construction drawings of your building project. Who is in Charge of the Project? Before you begin construction, the committee, contractor or minister who is in charge of the project needs to have a set of clear, proper scale drawings of the septic design. These construction drawings are needed to get approval to build a septic system for churches and theaters. These plans once approved by the local health department will usually allow for building permit approval. The plans are also used to get bids from several licensed contractors if needed. Important; In most areas land owners can prepare their own drawings and build their septic system without having a license to do either. State and local laws tell you if you can do this yourself or if you must hire an expert. Read this disclaimer before getting started. If you are unclear about your rules, call your county or parish health department and ask for the rules in your area. These are often available online along with permit forms and application fees.

A Septic system for assembly buildings present a special difficulty: Churches and Theaters share a common problem with resorts; intermit-tent flows. During special days there can be excessive crowds followed by days of almost no activity. Owners of assembly buildings only want to build those septic tanks and drainfields they need but often the numbers dictate that a larger system may be mandatory. Regulations are based on calculated daily flow based on full occupancy. Full occupancy in churches and most theaters happens less than weekly. Every seat is seldom filled for more than a few days per week at the busiest, yet the septic system is designed to handle full occupancy on a daily basis.

A septic system wants steady flow and normal waste strength. An apartment building is a good example of steady flow and normal waste strength. Restaurants have high waste strength. Hot water with excessive grease will kill a septic system faster than almost anything. A church with a large kitchen will deliver an intermittent load of high strength waste into the septic system. Be prepared to discuss how you will mitigate waste strength and intermittent flow with local health. Depending on their rules, they may not show you much mercy with the septic design.

Solving the Problem of Intermittent Flows: There are three basic strategies to even out occasional high loads.

1. Surge Tanks: Large underground storage tanks can be included in the design to store the treated effluent from the septic tank for sending to the drainfield in timed doses over the next few days following the holiday or other well attended event. This allows a smaller overall system but the surge tank must be professionally engineered. This type of system can wind up being more expensive than other options, and space for the surge tank must be found.

2. Enlarged Drainfields: Making the drainfield bigger is an obvious answer. However, an oversized drainfield will not work very well to remain healthy under normal low flow conditions.

3. Combinations of the two choices above: Utilizing smart control panels and remote valves, effluent can be delivered to the drainfield in timed doses to the capacity of the system. However excessive flows can be detected and redirected to surge tanks and then to specially designed drainfields built to accommodate surge conditions.

With our generic templates (The GTO System,) we provide you with examples of all three types of systems including pumping calculations and all the construction details. 

Where Do We Come Up With the Size of Our System? The USEPA Onsite Wastewater Treatment Systems Manual known in the trade as the Purple Manual, is the most used reference to set the minimum standards for system flows and many other things related to septic in the US.  The Purple manual has basically two methods to determine flow rates;

1. Fixture Flow Rates in Table 3-3 on page 7 of the Purple Manual, you will find various flow rates per hour for various residential plumbing fixtures. Once a flow rate/ fixture per day or sometimes flow rate/ person/ fixture/ day is agreed upon with the health people you can total up all fixtures and rates and arrive at a total gallons of sewage/ day (GPD.) The wide range of possible flow conditions usually tends to result in complex discussions and predicts larger flows than actually happens once built. Better to use flow rates based on occupancy or "Building Use."

2. Building Use Flow Rates in Table 3-4 on page 9 of the EPA Manual you can see all the possible uses such as "Resort Cabin," "Theater," "Country Club/ guests and employees."  For example, Patrons for a theater could use 3 gallons per seat per performance. A food service would use a figure more like 10 gallons of toilet and kitchen waste per patron. The number of patrons could be based on the number of seats times the number of meals served each day per seat. These numbers and details are generally somewhat negotiable with the local health people who will review your plans. Be prepared to dicker for what you want (possibly a smaller or less complex septic system) and come to any meeting prepared with clear plans in hand. 

Our package of drawings will suggest how you might show the flow rates for your church or theater, how big a tank is likely to be required and other details specific to your project. Professional drawings will help you make your case to the health department so they can determine the best system for your area. You will see what is required in our generic examples. For instance the theater above has a public occupancy of 200 people, 50 backstage actors and crew, three full time daily employees plus a limited snack food and beverage service in the lobby. With a 3000 gal surge tank (enough for two full days of storage,) the size of the pumping system, drainfield and replacement area can all be more than halfed.

Another example shows the church at the top of the page with hall seating for 300, a full commercial kitchen and a daytime  classroom for 30 children, three full daytime staff plus a managers unit with two bedrooms.  Using the drawing template package for a septic System for Theaters and Churches we discover that the subject church has a sewage flow rate of 3,120 gallons per day (GPD.) This rate requires a septic tank of at least 3,120 x 2 = 6,240 gallons. This tank is shown to the right and is a pre-cast concrete, traffic bearing model with concrete risers and cast iron lids. The tank is 17 ft long, 10 ft wide and 9.5 ft deep and is ordered from a local pre-cast concrete company and assembled on the site of four major parts. Costs for these tanks delivered these days is around $1 per gallon (6000 gal tank = $6,000) depending on lid arrangements. Cast-in-place tanks framed and poured on the site can not usually compete for price in this size range with pre-cast tanks.  

Next to the tank is a 1500 gal duplex (two pumps) pump chamber. Each pump delivers effluent to the drainfield through the white PVC transport lines seen heading past the inlet manhole on the septic tank at the bottom right of the picture. The small tractor at the top of the picture is running the generator which will provide electric power to the two pumps for a squirt test of the system for the health department inspection. In your plans you will be required to specify the exact size and layout of the septic tanks and pump chambers and the alignment, depth and drainage slope of all pipes. 

This Photo is looking down into the commercial duplex pumping system above. The the two turbine pumps (at the bottom of the view) are housed inside a one piece pump basin (blue PVC plastic) resting on the floor of the tank. The larger round chamber between the 1 1/2 inch diameter PVC transport lines contains a final plastic filter and can be slid up and out of its tube for inspection and cleaning. The float tree can be seen inside the filter chamber clipped to the pull-up handle on the right.

The blue basin is a custom length to match the top of the tank exactly. Our drawings show how one can specify all of the items required for most situations, although designing a larger system is something one should work up to if the designer has experience only with single home and small commercial systems. 

Commercial systems benefit greatly from duplex pumping. With two pumps in the system taking turns, if one pump quits in the middle of the night, you will not wake up to sewage on the ground (SOG.) The secondary (lag) pump will take over from the lead pump and keep the system operating for days if necessary until repair parts arrive.

You can see the control panel for the septic system for this assembly building in the corner ten feet to the left of the kitchen fan/vent. The close-up shows what is inside. The two light grey boxes on the upper left read out the elapsed time each pump has run in hundredths of an hour. The darker box upper middle is the logic control with a small screen and programming buttons (the brains.) Next to the right are the relays for each pump. Below them are the disconnect/ overload breakers plus the colour coded float and pump connections. The two toggles on the right control each pump individually and in three modes - on / off / and Auto. The system pumps should always be set to Auto if water is connected to the building. Leaving the pumps off for any reason such as saving power will surely lead to the flooding of the pump chamber when the building is occupied and no one remembers to turn on the system.

Grease Interceptors are Required in all Commercial Kitchens. This is for your own protection, and your drainfield because grease clogs the system and is hard for it to digest on good days. In the past a small grease pit in the floor was OK. Now we understand the role grease can play in a commercial system and we use much larger grease trap units accessible from outside the building. The software explains how to design the grease 

interceptor or grease trap for the size and needs of your kitchen. In general a 1000 gallon interceptor is about minimum size and it's outside dimensions are the same as for a 1000 gal septic tank. The grease trap requires that the kitchen sewer is separated from the sewer for the bathrooms and other domestic uses.  

No Garbage Grinders or Floor Drains Allowed: Large commercial garbage grinders like the one pictured to the left have no place hooked up to a septic system. Pulverized vegetables have the same density as water and will flow through the baffles and traps in the septic tank without adequate reduction of sewage strength. It is recommended to use commercial garbage collection to eliminate organic kitchen waste in a septic system for churches and theaters with food service. 







A Septic System for Churches and Theaters Last Revised: 11/11/2016 

all words and images copyright © 2009-2016 ECO-NOMIC INC. All rights reserved.








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