Category PLUMBER’S AND. PIPE FITTER’S. CALCULATIONS MANUAL

Problems with a leach field are uncommon among new installations. Unless the field was poorly designed or installed improperly, there is very little rea­son why it should fail. However, extremely wet ground conditions, due to heavy or constant rains, could force a field to become saturated. If the field saturates with ground water, it cannot accept the effluent from a septic tank. This, in turn, causes backups in houses. When this is the case, the person who created the septic design should be looked to in terms of fault.

Older Fields

Older fields sometimes clog up and fail. Some drain fields become clogged with solids. Financially, this is a devastating discovery. A clogged field has to be dug up and replaced. Much of the crushed stone might be salvageable, but the pipe, the excavation, and whatever new stone is needed can cost thou­sands of dollars. The reasons for a problem of this nature are either a poor de­sign, bad workmanship, or abuse.

If the septic tank installed for a system is too small, solids are likely to en­ter the drain field. An undersized tank could be the result of a poor septic de­sign, or it could come about as a family grows and adds onto their home.

A tank that is adequate for two people may not be able to keep up with the us­age seen when four people are involved. Unfortunately, finding out that a tank is too small often doesn’t happen until the damage has already been done.

Why would a small septic tank create problems with a drain field? Septic tanks accept solids and liquids. Ideally, only liquids should leave the septic tank and enter the leach field. Bacterial action occurs in a septic tank to break down solids. if a tank is too small, there is not adequate time for the breakdown of solids to occur. increased loads on a small tank can force solids down into the drain field. After this happens for a while, the solids plug up the drainage areas in the field. This is when digging and replace­ment is needed.

in terms of a septic tank, a pipe with a fast grade can cause solids to be stirred up and sent down the outlet pipe. When a four-inch wall of water dumps into a sep­tic tank at a rapid rate, it can create quite a ripple effect. The force of the water might generate enough stir to float solids that should be sinking. If these solids find their way into a leach field, clogging is likely.

We talked a little bit about garbage disposers earlier. When a disposer is used in conjunction with a septic system, there are more solids involved that what would exist without a disposer. This, where code allows, calls for a larger septic tank. Due to the increase in solids, a larger tank is needed for satisfac­tory operation and a reduction in the risk of a clogged field. I remind you again, some plumbing codes prohibit the use of garbage disposers where a septic system is present.

other causes for field failures can be related to collapsed piping. This is not common with today’s modern materials, but it is a fact of life with some old drain fields. Heavy vehicular traffic over a field can compress it and cause the field to fail. This is true even of modern fields. Saturation of a drain field will cause it to fail. This could be the result of seasonal water tables or pro­longed use of a field that is giving up the ghost.

Septic tanks should have the solids pumped out of them on a regular ba­sis. For a normal residential system, pumping once every two years should be adequate. Septic professionals can measure sludge levels and determine if pumping is needed. Failure to pump a system routinely can result in a build­up of solids that may invade and clog a leach field.

Normally, septic systems are not considered to be a plumber’s problem. Once you establish that a customer’s grief is coming from a failed septic sys­tem, you should be off the hook. Advise your customers to call septic profes­sionals and go onto your next service call; you’ve earned your money.

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ational rainfall statistics are needed for computing the requirements of storm water systems. The expected rainfall rates are needed to fig­ure out systems for roof drains, storm sewers, and similar methods of controlling storm water drainage. Fortunately, the rainfall rates for major cities are listed in this chapter. Similar information can often be found in plumbing codebooks. You will also find rain maps in this chapter and some codebooks. You can’t accomplish much with only the rainfall rates. Consider the following information as reference material that you can use at anytime to compute the needs for controlling storm water. (Figs. A1.1 to A1.5)

309

Virginia Bristol 2.7 Charlottesville 2.8 Lynchburg 3.2 Norfolk 3.4 Richmond Washington 3.3 Omak 1.1 Port Angeles 1.1 Seattle 1.4 Spokane 1.0 Yakima West Virginia 1.1 Charleston 2.8 Morgantown Wisconsin 2.7 Ashland 2.5 Eau Claire 2.9 Green Bay 2.6 La Crosse 3.1 Madison 3.0 Milwaukee Wyoming 3.0 Cheyenne 2.2 Fort Bridger 1.3 Lander 1.5 New Castle 2.5 Sheridan 1.7 Yellowstone Park 1.4

FIGURE A1.1 ■ (Continued) Rainfall rates.

OJ GO

FIGURE A1.5 ■ Rainfall intensity-duration-frequency charts. (Courtesy of McGraw-Hill)

Wichita. Kansas
«Podge City, Kansas’	■Topefcs. Kansas
Shreveport, Louisiana
^Lexington, Kentucky;	і Louisville, Kentucky	New Orleans, Louisiana
•Portland, Maine	.Baltimore, Maryland	■Boston, Massachusetts
‘Eastport, Maine
	■Detroit Michigan	-East Lansing, Michigan
;Alpena, Michigan;
•Escanaba, Michigan
■Grand Haven, Michigan	•Grand Rapids, Michigan	‘Houghton,
|Sault Ste. Marie, Michigan	Duluth, Minnesota.
[Marquette, Michigan
•Moorhead, Minnesota
[Minneapolis, Minnesota	]St. Paul,.Minnesota1	[Meridian, Mississippi
[Colombia, Missouri	Hannibal, Missouri	•Kansas City, Missouri
Vicksburg, Mississippi;
Missouri	‘яїоак.’Missouri
Minutes Duration

Miss dull, Montana
Каи spell, Montana
;Omaha, Nehraska!
;Lincoln, Nebraska	■North Platt», Nebraska
Atlantic City, New Jersey
.Winnenuicci, Nevada	■Concord, New Hampshire]
T re ntonNewTersoy
■SmghamtQ. n, New York
Fe, New Mexico
Oswego, ftewYoTk
.Rochester, New’York	-Asheville, North Caroline-	^Charlotte, North
■Raleigh, North Carolina
filming ton, North
Greensboro, North Carolina^
;&evils Lake, NorthDskota"
Bismarck, Norl

‘Cleveland, QbfO	■ Sandusky. Ohio
‘Columbus, Ohio
.Portland, Oregon
■Roseburg, Oregon	Erie, Pennsylvania	IHamsburs	Philadelphia, Pennsylvania
Шоск island Rhode Stand
Pennsylvania	Reading, Pennsylvania	[Scranton, Pennsylvania^
Greenville,’South СаюІівГ
■Columbia, South Carolina
‘Providenot, Rhode stand
Charleston South Carolina-
10
[Pierre, South D kota	■Yankton, Sou h Dakota’
Rapid City, South Dakota
[Chattanooga, Tennessee	■ Nashville, Tennessee1
•Knoxville Tennessee	; Mem phis, Tennessee;
■Amarillo, Texas-	[Brownsville, Texes
■ Corpus CbristJ, Texas –
Mmutes Duration

There are times, even with new systems, when the problem causing a whole – house backup is in the septic tank. These occasions are rare, but they do ex­ist. When this is the case, the top of the septic tank must be uncovered. Some tanks, like the one at my house, are only a few inches beneath the surface. Other tanks can be buried several feet below the finished grade.

Once a septic tank is in full operation, it works on a balance basis. The in­let opening of a septic tank is slightly higher than the outlet opening. When water enters a working septic tank, an equal amount of effluent leaves the
tank. This maintains the needed balance. But, if the outlet opening is blocked by an obstruction, water can’t get out. This will cause a backup.

Strange things sometimes happen on construction sites, so don’t rule out any possibilities. It may not seem logical that a relatively new septic tank could be full or clogged, but don’t bet on it. I can give you all kinds of things to think about. Suppose a septic installer was using up old scraps of pipe for drops and short pieces, and one of the pieces had a plastic test cap glued into the end of it that was not noticed? This could certainly render the septic sys­tem inoperative once the liquid rose to a point where it would be attempting to enter the outlet drain. Could this really happen? I’ve seen the same type of situation happen with interior plumbing, so it could happen with the piping at a septic tank.

What else could block the outlet of a new septic tank? Maybe a piece of scrap wood found its way into the septic tank during construction and is now blocking the outlet. If the wood floated in the tank and became aligned with the outlet drop, pressure could hold it in place and create a blockage. The point is that almost anything could be happening in the outlet opening, so take a snake and see if it is clear.

If the outlet opening is free of obstructions, and all drainage to the septic tank has been ruled out as a potential problem, you must look further down the line. Expose the distribution box and check it. Run a snake from the tank to the box. If it comes through without a hitch, the problem is somewhere in the leach field. In many cases, a leach field problem will cause the distribution box to flood. so, if you have liquid come rushing of the distribution box, you should be alerted to a probable field problem.

Whole-house backups (where none of the plumbing fixtures drain) indicate either a problem in the building drain, the sewer, or the septic system. There is no way to know where the problem is until some investigative work is done. It’s possible that the problem is associated with the septic tank, but you will have to pinpoint the location where trouble is occurring.

For all the plumbing in a house to back up, there must be some obstruc­tion at a point in the drainage or septic system beyond where the last plumb­ing drain enters the system. Plumbing codes require clean-out plugs along drainage pipes. There should be a clean-out either just inside the foundation wall of a home or just outside the wall. This clean-out location and the access panel of a septic tank are the two places to begin a search for the problem.

If the access cover of the septic system is not buried too deeply, I would start there. But, if extensive digging would be required to expose the cover, I would start with the clean-out at the foundation, hopefully on the outside of the house. Remove the clean-out plug and snake the drain. This will normally clear the stoppage, but you may not know what caused the problem. Habit­ual stoppages point to a problem in the drainage piping or septic tank.

Removing the inspection cover from the inlet area of a septic tank can show you a lot. For example, you may see that the inlet pipe doesn’t have a tee fitting on it and has been jammed into a tank baffle. This could obviously account for some stoppages. Cutting the pipe off and installing the diversion fitting will solve this problem.

Sometimes pipes sink in the ground after they are buried. Pipes some­times become damaged when a trench is backfilled. If a pipe is broken or de­pressed during backfilling, there can be drainage problems. When a pipe sinks in uncompacted earth, the grade of the pipe is altered, and stoppages become more likely. You might be able to see some of these problems from the access hole over the inlet opening of a septic tank.

Once you remove the inspection cover of a septic tank, look at the inlet pipe. It should be coming into the tank with a slight downward pitch. If the pipe is pointing upward, it indicates improper grading and a probable cause for stop­pages. If the inlet pipe either doesn’t exist or is partially pulled out of the tank, there’s a very good chance that you have found the cause of your backup.

In the case of a new septic system, a total backup is most likely to be the result of some failure in the piping system between the house and the septic tank. If your problem is occurring during very cold weather, it is possible that the drain pipe has retained water in a low spot and that the water has since frozen. I’ve seen it happen several times in Maine with older homes.

Running a snake from the house to the septic tank will tell you if the prob­lem is in the piping. This is assuming that the snake used is a pretty big one. Little snakes might slip past a blockage that is capable of causing a backup. An electric drain-cleaner with a full-size head is the best tool to use.

Some homeowners associate an overflowing toilet with a problem in their septic system. It is possible that the septic system is responsible for the toilet backing up, but this is not always the case. A stoppage either in the toilet trap or in the drainpipe can cause a backup.

If you get a call from a customer who has a toilet flooding their bathroom, there is a quick, simple test you can have the homeowner perform to tell you more about the problem. You know the toilet drain is stopped up, but will the kitchen sink drain properly? Will other toilets in the house drain? If other fix­tures drain just fine, the problem is not with the septic tank.

There are some special instructions that you should give your customers prior to having them test other fixtures. First, it is best if they use fixtures that are not in the same bathroom with the plugged-up toilet. Lavatories and bathing units often share the same main drain that a toilet uses. Testing a lava­tory that is near a stopped-up toilet can tell you if the toilet is the only fixture affected. It can, in fact, narrow the likelihood of the problem down to the toi­let’s trap. But, if the stoppage is some way down the drainpipe, it’s conceiv­able that the entire bathroom group will be affected. It is also likely that if the septic tank is the problem, water will back up in a bathtub.

When an entire plumbing system is unable to drain, water will rise to the lowest fixture, which is usually a bathtub or shower. so, if there is no backup in a bathing unit, there probably isn’t a problem with a septic tank. But, back­ups in bathing units can happen even when the major part of a plumbing sys­tem is working fine. A stoppage in a main drain could cause the liquids to back up into a bathing unit.

To determine if a total backup is being caused, have homeowners fill their kitchen sinks and then release all of the water at once. Get them to do this several times. A volume of water may be needed to expose a problem. Simply running the faucet for a short while might not show a problem with the kitchen drain. If the kitchen sink drains successfully after several attempts, it’s highly unlikely that there is a problem with the septic tank. This would mean that you should call your plumber, not your septic installer.

There are times when sewage pumps must be used to get sewage to a septic system. The pumps are normally installed in a buried box outside of the building being served. The box is often made of concrete. In these cases, the home’s sewer pipe goes to the pumping station. From the pumping station, a solid pipe transports the waste to the septic tank.

sewage pumps have floats that are lifted as the level of contents in the pump station build. When the float is raised to a certain point, the pump cuts on, emptying the contents of the pump station. The dis­charge pipe from the pump must be equipped with a check valve. otherwise, gravity would force waste down the pipe, back into the pump station, when the pump cut off. This would result in the pump having to constantly cut on and off, wearing out the pump.

There are some additional piping considerations for plumbers to observe. septic tanks are designed to handle routine sewage. They are not meant to modify chemical discharges and high volumes of water. If, as a plumber, you pipe the discharge from a sump pump into the sanitary plumbing system, which you are not supposed to do, the increased volume of water in the tank could disrupt its normal operation.

GAS CONCENTRATIONS

Gas concentrations in a septic tank can cause problems for plumbers. The gases collected in a septic tank have the poten­tial to explode. If you remove the top of a septic tank with a flame close by, you might be blown up. Also, breathing the gases for an extended period of time can cause health problems.

What about garbage disposers, do they hurt a septic system? The answers offered to this question vary from yes to maybe to no. Many people, including numerous code enforcement offices, believe garbage disposers should not be used in conjunction with septic sys­tems. Other people disagree and believe that disposers have no adverse effect on a septic system.

it is possible for the waste of a disposer to make it into the distribution pipes and drain field. If this happens, the risk for clogging is elevated. An­other argument against disposers is the increased load of solids they put on a septic tank. Obviously, the amount of solid waste will depend on the fre­quency with which the disposer is used.

What is my opinion? My opinion is that disposers increase the risk of sep­tic system failure and should not be used with such systems. However, I know of many houses using disposers with septic systems that are not experiencing any problems. If you check with your local plumbing inspector this question may become a moot point. Many local plumbing codes prevent the use of dis­posers with septic systems.

How can clogs be avoided? Clogs can be avoided by careful attention to what types of waste enter the septic system. Grease, for example, can cause a septic system to become clogged. Bacteria does not do a good job in breaking down grease. Therefore, the grease can enter the slotted drains and leach field with enough bulk to clog them.

Paper, other than toilet paper, can also clog up a septic system. If the paper is not broken down before entering the drain field, it can plug up the works.

WHAT ABOUT GARBAGE DISPOSERS,

How does a septic system work? A standard septic system works on a very simple principle. Sewage from a home enters the septic tank through the sewer. Where the sewer is connected to the septic tank, there is a baffle on the inside of the tank. This baffle is usually a sanitary tee. The sewer enters the center of the tee and drops down through the bottom of it. The top hub of the tee is left open.

The bottom of the tee is normally fitted with a short piece of pipe. The pipe drops out of the tee and extends into the tank liquids. This pipe should never extend lower than the outlet pipe at the other end of the septic tank. The inlet drop is usually no more than twelve inches long.

The outlet pipe for the tank also has a baffle, normally an elbow fitting. The drop from this baffle is frequently about sixteen inches in length.

When sewage enters a septic tank, the solids sink to the bottom of the tank and the liquids float within the confines of the container. As the tank col­lects waste, several processes begin to take place.

SEPTIC TANK MAINTENANCE

Septic tank maintenance is not a time consuming process. Most septic sys­tems require no attention for years at a time. However, when the scum and sludge layers combined have a depth of eighteen inches, the tank should be cleaned out.

Trucks equipped with suction hoses are normally used to clean septic tanks.

The contents removed from septic tanks can be infested with germs. The disease risk of exposure to sludge requires that the sludge be handled carefully and properly.

Mound systems, as you might suspect, are septic systems that are constructed in mounds that rise above the natural topography. This is done to compen­sate for high water tables and soils with slow absorption rates. Due to the amount of fill material to create a mound, the cost is naturally higher than it would be for a bed system.

Coarse gravel is normally used to build a septic mound. The stone is piled on top of the existing ground. However, topsoil is removed before the stone

is installed. When a mound is built, it contains suitable fill material, an ab­sorption area, a distribution network, a cap, and topsoil. Due to the raised height, a mound system depends on either pumping or siphonic action to work properly. Essentially, effluent is either pumped or siphoned into the dis­tribution network.

As the effluent is passing through the coarse gravel and infiltrating the fill material, treatment of the wastewater occurs. This continues as the liquid passes through the unsaturated zone of the natural soil. The purpose of the cap is to retard frost action, deflect precipitation, and to retain moisture that will stimulate the growth of ground cover.

Mounds should be used only in areas that drain well. The topography can be level or slightly sloping. The amount of slope allowable depends on the perk rate. For example, soil that perks at a rate of one inch every sixty minutes or less, should not have a slope of more than six percent if a mound system is to be installed. If the soil ab­sorbs water from a perk test faster than one inch in one hour, the slope could be increased to twelve percent. These numbers are only examples. A profes­sional who designs a mound system will set the true criteria for slope values. Ideally, about two feet of unsaturated soil should exist between the original soil surface and the seasonally saturated topsoil. There should be three to five feet of depth to the impermeable barrier. An overall range of perk rate could go as high as one inch in two hours, but this, of course, is subject to local ap­proval. Perk tests for this type of system are best when done at a depth of about 20 inches. However, they can be performed at shallow depths of only 12 inches. Again, you must consult and follow local requirements.