Septic Tank Installation and Maintenance

How does a Septic Tank Work?

A Septic Tank is a storage chamber that slows down the flow of sewage effluent through the tank unit so that solids are deposited at the bottom of the tank and any floating scum is trapped on the surface of liquid level in the tank. The outlet is designed so that only the non-scum, non-solid fraction of the sewage effluent is discharged - usually into a soakaway system below the ground surface.

A traditional septic tank with a single chamber fitted with single inlet and outlet 'T' pipes is shown in the diagram opposite.

When sewage enters the septic tank unit, two processes occur. Gravity pulls the solids in the sewage to the base of the tank and anaerobic bateria produce a scum layer on the surface.
The result is that what leaves the tank via the outlet pipe is effluent with a very low solids content. This effluent can then cascade into a second or third chamber which then leads to a ground soakaway system.

A modern moulded septic tank is shown in the lower digram opposite. This type of tank has internal baffles which reduce the flow and allow solids to settle to the base for periodic removal.

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Can I upgrade my existing Septic Tank?

If a higher-level of effluent cleanliness is required than a septic tank can provide, it may be necessary to replace the tank with a sewage treatment plant. This may involve significant on-site work and be quite expensive.

An alternative to full replacement is to retro-fit a secondary treatment unit such as the "UniGem" which is fitted to existing septic tanks and some cesspits/cesspools that have sufficient existing volume for sludge containment and uses an aerator and bacteria design with no need for additives.



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What size should my Septic Tank be?

As the main purpose of a septic system is to remove solids and only allow liquid effluent to discharge into the soakaway system, the size, style and construction of your septic tank will depend on the volume of effluent produced in a given time. A common problem is the original septic tank being too small for current usage. In recent years, household water usage has increased and we now produce higher volumes of waste water.

The average family house should have a septic tank system with a total holding capacity of approximately 1000 gallons (4 500 litre).

If a septic tank is too small then you are likely to reduce the life of your soakaway system. Black Water Solutions can advise you on the best septic tank style and size to suit your current and expected future requirements.

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Can I use bleach or detegent with a Septic Tank installation?

If you have a modern septic tank unit, using normal daily quantities of bleaches and detergents should not be a problem.

However, more traditional septic tank systems are more adversely affected by bleaches and detergents as they tend to kill the anaerobic bacteria essential for its operation. Also, if the tank is of a small capacity or has only one chamber, then we can find soakways becoming blocked and hence having a lower lifespan.

Contact Black Water Systems to advise you further on your septic tank system.

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Is a Septic Tank Smelly?

A sectic tank should not smell. However, in our experience, is in not uncommon to get the occasional unpleasant odour. Persistent odours are probably due to lack of maintenance and / or the septic tank being of inadequate capacity or damaged. We can help with surveying such problems and carry out the appropriate remedial work, where possible.

Black Water Solutions can fit air-tight access-covers which may prevent smells originating from septic tanks that are basically functioning correctly.

Always check the location of a septic tank in a newly-purchased property - if located too close to the house, then unpleasant odours can be a problem - especially on a hot day.

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Does a septic tank need to be emptied?

Yes - a septic tank needs emptying at least once a year.

Solids build up in septic tank systems, and they need to be removed periodically. Otherwise, they can build up in volume and cause the soakaway system (usually under your garden!) to get blocked with solids.

Black Water Solutions can carry out septic tank emptying for you as part of an annual service plan - please enquire for details.

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Is my existing Septic Tank working properly?

Here are some common problems with septic tanks:

• Backing-up of sewage in the drainage pipe and manholes.
• Flooding of effluent over the tank access covers.
• Dark effluent with an unpleasant odour visible at or near the tank.
• A combination of all of the above factors.

If a septic tank system is not effectively separating solids and liquid, then the soakaway will, in time be blocked.

So if the daily rate of dissipation of effluent by the soakaway is less than the volume of sewage entering the tank per day, then sewage will build up pipes and manholes and may break out onto the surface.

In such cases, a simple de-sludge of the tank and, if possible a jet clean of the soakaway, may be sufficient to cure the problem. However, our experience is that some repair work to the soakaway will also be necessary.

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What does a Septic Tank Cost?

Please call us or email us for our current charges as we are currently reviewing these.

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