Concrete Septic Tank Cost - Septic Tank Sewage Treatment Systems - These present a no question incompetent method of treating sewage for properties which are not joined to mains drainage. Many septic tank systems throughout the world are never maintained and suitably realize not doing properly and pollution direct laws exist to try to limit the amount of environmental and health risks they cause. These laws are getting tighter, and minimum standards have been put in place for new or replacement septic systems. In many cases you will compulsion to install a sewage treatment reforest system instead. Always get the sewage system checked by a waste water system proficient prior to purchasing a property in order to prevent a pollution problem.
Types of Septic Tank Systems Available
There are various types of septic tank systems. They consist of an underground septic tank in differing shapes and sizes, which subsequently connects to a additional soil treatment system, usually a house drainage system in the form of a soakaway or drainfield, or a mound soakaway.
How a Septic Tank works
Raw sewage and waste water from baths, kitchens, etc. discharges into the tank, where the solids are divided from the liquid waste. Fats and oils float to the summit of the tank and form a crust layer. Faeces and food scraps sink to the bottom of the tank and form a sludge layer. Anerobic bacteria which are natural colonisers in the tank "digest" this sludge by occurring to 70%.
The filthy septic water flows out of the tank to a soakaway or drainfield. Baffles or 'T' pipes in the tank hold encourage the drifting crust and prevent it from entering the outlet of the tank. In order that the sludge and crust layers realize not become too deep, septic tanks should be emptied annually. This then prevents a far along and far along inclusion of suspended solids washing out into the soakaway. Solids can block the ventilate spaces in the soil drainage system, creating a drainage misery and the septic tank effluent will not be competent to soak away or be treated by the natural soil bacteria.
Variations in Septic Tank systems
Traditional septic tanks comprise of two rectangular chambers: the first one instinctive 2/3 of the sum up and the second 1/3, usually built in brick or concrete. Strict design rules are in place and septic tanks must be expected in accordance later BS 6297 1983. The inlet pipe into the first chamber ends in a 'T' pipe which travels next to the at least 450mm (18") below summit water level (TWL), and the chamber must be a minimum of 1500mm (5'-0") deep from TWL. This first stage chamber is usually twice as long as it is wide. The pipe from the first chamber into the second chamber consists of an 'H' pipe and the bottom of the pipe is a min. of 300mm (12") below TWL in the first chamber and 450mm (18") below summit water level (TWL) later it enters the second chamber.This second stage chamber is usually square. The outlet pipe from the second chamber of the tank then consists of a 'T' pipe later the bottom of the pipe 300mm (12") below TWL.
Vent pipes should be installed from the first and second chambers for venting the gases, mainly methane and hydrogen sulphide, that are produced by the sludge. mighty covers should always be placed no question greater than a septic tank to avoid kids / animals falling into the tank. There are many cases of thcovers collapsing and many people have been killed as a result.
Nowadays, septic tanks are made in GRP and polyethylene which commonly are spherical in involve later a narrow shaft at the summit to a manhole auditorium level. These realize not produce the similar vibes of effluent as two chamber tanks and cannot be placed in front of many conversion units.
Care should be taken to ensure that problems will not occur due to the tank rising out of the ground, later it is emptied in high water table sites. It is always advisable to install the tank later a tangible surround.
Septic tank effluent still contains about 70% of the pollutants in the indigenous sewage and needs new treatment in the soakaway to prevent a pollution problem.
Soakaways and Septic Drainfields
The Septic Tank only provides the first allowance of the sewage treatment process. The soakaway is the underground soil treatment system which uses aerobic bacteria found naturally in the auditorium to new treat the effluent. The soil type must be welcome for a soakaway to doing properly. Percolation tests are required to determine whether a septic tank soakaway is suitable. If the soil is clay, it is not welcome for a soakaway and a drainage misery is inevitable. If you have this misery subsequently a sewage treatment reforest is the answer as they realize not compulsion a soakaway.
The soakaway consists of either a series of trenches containing perforated pipe laid on and surrounded by stone, or an absorption bed, or a soakaway mound, all of which are joined to the septic tank outlet by a pipe. In all cases the soakaway must be a minimum of 1.2 metres above the water table or bedrock at all times. They must then be a minimum of 200 mm. below auditorium level to avoid septic effluent breaking to the surface. The pipes should be laid at a gradient of no more than 1:200 in a drainfield in order that the wastewater does not direct to the end of the pipe, but is dispersed evenly. The perforations should be larger than 6mm (0.25") to avoid the biomatt, which forms in the trench, blocking the holes. The pipe cannot be the corrugated tubing type as used in house drains as this is not allowed, but must be the truthful solid soakaway drainage pipe
The contaminants, pathogens, nutrients, and organic situation in the effluent are dispersed into the gravel where they are digested by aerobic bacteria.
On a oblique site, the effluent may flow into a series of drop boxes or manholes later substitute outlet to the next-door pipeline set at a degrade level. Absorption beds are useful where expose is limited, but they should only be used as a second choice.
Sewage Drainage Mounds
A treatment mound is a raised soakaway system. Aggregates are used to lift the soakaway suitably that it is at least 1200mm (4'-0") above the seasonal high water table or bedrock. The mound system must be expected carefully, taking into account the topography of the site, the volume of septic tank effluent to be treated and the porosity of the topsoil to avoid failure of the system and boggy areas approximately the base of the mound. The design cannot be guessed and must be curtains by a trained professional, using exam results and calculations.
I have seen dreadfully expected mounds blast a hole through the side as they have been too little for the job.
Effluent is piped to a pumping station tank, where it is pumped in batches into the mound pipe-work. Septic mounds can look no question attractive and can form allowance of the landscaping of a garden. You are not allowed to reforest shrubs on summit of them, but they can be planted approximately their base.
Septic Tank Soakaway Pits
In the past, many septic tank systems used soakaway pits, although these pits are no longer sufficient below highly developed building regulations. They consisted of a large hole in the ground, gate at the bottom, either blocked circular later gaps with the blocks to allow seepage of the effluent into the soil, or clearly holes filled later stones. Some soakaway pits were made of large tangible rings later gaps with the rings and the septic tank effluent was piped into them. They were always covered, usually later a large tangible slab, but they were often a failure, as no calculations were undertaken to determine the porosity of the surrounding soil and they soon were filled later septic effluent. The drains subsequently fill with the pit and the tank, which backs-up the entire septic system.
Site Conditions and Installation
Most sites in the UK are not welcome for septic tank systems. Either the soil contains too much clay or is too porous, or the winter water table or bedrock is too near the surface. If the soil is clay, subsequently it will not soak the septic effluent away and if it is too coarse it will not hold the effluent long sufficient for treatment. You could judge a non-electric sewage treatment reforest instead. Sometimes, it is practicable to accustom yourself a septic system to exploit a basically improper site, but this requires careful planning and design by an expert. As a general rule, if the site has either insufficient soil depth, or the incorrect type of soil, it is not welcome for a septic system. Always gate your Building Inspector past deciding on a septic system.
The size of a septic system, both the tank and the soakaway area, is definite by the number of bedrooms in the house and porosity of the soakaway soil. A septic system cannot doing if it is overloaded, suitably always bear in mind any plans you may have for extending the property past you judge on the size of the septic system. Increasing the size far along results in a ruined garden.
Finally, always check later the vibes Agency and you local Building direct past deciding on a septic system. They will have a no question fine idea as to whether it is likely to doing in your place and could keep you thousands of pounds in replacing an improper septic installation.