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This page contains answers to some frequently asked questions (FAQ's) regarding domestic sewerage treatment, drinking water treatment and UV technology.

  1. Do I have to use any special type of detergents and washing powders?
  2. The greatest causes of problems with your treatment plant are cleaning products and the washing machine.

    PLEASE NOTE:  The following information is not intended to promote or discredit the product of any Company.  It is provided to assist in ensuring the satisfactory on-going operation of your system. To protect the environment and ensure the longevity and optimal performance of your Nature Flow® HSTP we recommend that you use environment friendly detergents and cleaners.  

    Using cleaners and detergents that contain high levels of ammonia (eg bleach) and/or phosphorus is hazardous to the biological health of your HSTP.  These types of cleaners kill off the natural bacteria and micro-organisms used to treat the primary effluent.  Reduction of the natural bacteria of your HSTP will result in a much lower level of primary treatment and may produce unpleasant “septic” odours.  High levels of nitrogen and phosphorus also contribute to the growth of algae and other less desirable micro-organisms in the environment eg algal growth in waterways.

    Info sheets - Do's & Don'ts and Toilet Paper

    We highly recommend visiting this independent website www.lanfaxlabs.com.au for further information on laundry products.  They have a concise, comprehensive and independent brochure detailing laundry products that is available for free download. 

  3. Do I have to establish garden beds for disposal of treated effluent?  Do I need to do any special landscaping?
  4. This is subject to your site assessment for effluent disposal.  The need for garden beds, diversion/retention mounds, soil improvement etc will be ascertained by your site assessor based on the soil type of your property, property size, ability to comply with setback distances, hydraulic loading of residence etc.

Special landscapiing is not generally required as this is usually identified in your site assessment.  However since HSTP's are commonly installed at an early stage of construction it is sometimes difficult to provide advice with regard to landscaping requirements.  

It is advisable to ensure that stormwater run-off is diverted away from the media filter and treatment tank.  This is to limit the entry of excess water which does not require treatment hence increasing the lifetime of your HSTP.  Owners who are concerned with possible stormwater run-off should talk to their sewerage site evaluator or HSTP installer and advise them of their concerns - discussion of diversion options can then take place.

As a general rule, if it becomes apparent that stormwater run-off flows in the direction of the media filter and sewerage tank some landscaping will be required to divert this flow.  This may be in the form of a diversion mound - a raised mound of grass/mulch covered soil to divert water flow away from the HSTP or a cut-off drain.  Alternatively diversion mounds may be designed in the form of garden beds .

  1. Does chlorine kill my plants?
  2. The Nature Flow® Mk II Budget HSTP with online chlorinator uses chlorine to disinfect effluent prior to dispersal. The chlorinator used is a dial-up model. This ensures that only the minimum amount of chlorine needed to effectively disinfect the effluent is used thus minimising the discharge of chemical into the environment. This also means that the chlorine residual remaining in the treated effluent is minimal and as such irrigation of plants and lawns is not adversely affected. Ie Irrigation with treated effluent from the chlorinator model will not kill your plants or lawn.

  3. How often does my system need servicing?  Do I have to get my system serviced?
  4. All Nature Flow® Systems only require annual servicing in standard domestic applications. Annual services cost approximately $125 plus travel and any consumeables and are completed by our service agent.

    Servicing is mandatory and a condition of your approval to install.  It is a local authority (council) requirement according to AS1547:2000 - Onsite Domestic Wastewater Management. Penalties apply to anyone infringing this requirement and spot checks are a regular occurrence.

  5. What else is involved in maintaining my system?
  6. Apart from the annual service Nature Flow® Systems require minimal intervention by the homeowner.

    The Nature Flow® Mk II Budget HSTP uses specialised chlorine tablets for disinfection. Generally, a standard household of 4 to 6 people uses 5 chlorine tablets a quarter. A pack of 5 chlorine tablets costs approximately $10. Therefore an average expense of $40 per year for chlorine tablets. The homeowner can replenish the chlorine tablets – a service call-out is not required. Instructions are available in the owners manual. No other maintenance is required.

    The Nature Flow® Mk II Ultra Violet HSTP uses UV sterilisation for disinfection. In a standard domestic application, the UV globe will require replacement approx. every 3 years at an approximate cost of $161.70* incl GST excluding packaging and freight, a service kit will also be required at this time (o'rings & felts) - approx $35* incl GST. We recommend that a service technician complete any UV lamp changes. To minimise costs this lamp change may be completed during an annual service. No other maintenance is required.

    The disposal field must be maintained eg keep grass mown and ensure sprinklers are uncoiled and in good operational condition.  Where subsurface disposal is utilised there may be in-line filters that require periodical cleaning.  Ensure signage is maintained.

  7. What happens when I go on holidays?

    The system’s power consumption is directly linked to use of the treatment plant.  

    Submersible pumps operate in relation to inflows into the treatment plant.  Pumps may continue to operate during periods of non-occupation due to ingress of stormwater/rainfall into the media filter bed.  While their operation will obviously be reduced during periods of non-use they must not be turned off to ensure that any water ingress into the treatment plant (outside household flows) may be disposed off.  

    The control box operates continuously using minimal power.  It must remain turned on at all times.  The control box alerts the homeowner to high levels in the treatment plant and/or UV lamp degradation.

    The treatment plant is robust and has the capacity to handle periods of non-use without the need for “reactivation”.  Simply commence using the system as usual.  (Ensure that power to the system is on and that disposal hoses (surface irrigation) are connected and unrolled.)  

    Servicing periods remain mandatory and intervals are not reduced due to periods of non-use.

  9. How much electricity does this system use?
  10. The Nature Flow® System in a standard domestic application uses approx $51 to $77 of electricity per year*.  

    Note that calculations have been based on a full 10EP loading of 2500L/Day based on 250 litres per person per day. However due to recent social and/or legislative changes regarding water use in the home and specifically the use of water saving devices the daily loading rate (10EP) is expected to reduce to an estimated average of 1500L - 1700L per day based on 150 or 170 litres per person per day.  

    Thus a standard domestic household of 6 EP could be expected to generate daily flows of between 900-1020 L/Day which would result in less than half the electricity consumption calculated below.

    Nature Flow UV HSTP    $154.02/yr*

    Nature Flow Budget HSTP    $102.02/yr*

    Assumptions:  Full 10EP Loading - 2500L/Day

    125 Minutes running per Day, based on 2500L/Day @ 20L/minute, 52 Weeks / Year @ 18c per kWh

    Controller Amps, based on normal state, NO Alarm state. Therefore visual or audible alarm currents not taken into account.  Operating times rounded up to nearest minute.  Pumps are Davey D25A submersible pumps.

    There are two pumps used in the system. One for pumping effluent through the media filter to the disinfection chamber of the tank and the other to pump from the disinfection through the chlorinator or UV unit to the dispersal method. These pumps do not operate 24 hours/day. They only operate as required and are activated by a float switch when a certain level is reached in the tank. 

* Based on 6EP 1500-1700L/day.  Subject to change depending on current tarrifs, actual hydraulic loading and pumps used.

  1. How do these systems protect the environment?

The Nature Flow® Mk II Budget HSTP with online chlorinator uses chlorine to disinfect effluent prior to dispersal. The chlorinator used is a dial-up model. This ensures that only the minimum amount of chlorine needed to effectively disinfect the effluent is used thus minimising the discharge of chemical into the environment.

The Nature Flow® Mk II Ultra Violet HSTP uses ultra violet sterilisation to treat wastewater.  UV sterilisation is Nature's own method of disinfection.  It does not introduce any chemicals or disinfection by-products into the environment.  It is safe, effective and efficient.  Treated effluent is odourless and disinfected to a very high standard.

  1. Do these systems treat black and grey water? Do I need a greasetrap?

Yes. Nature Flow® HSTP’s treat all black and grey water and eliminates the need for a greasetrap. It is an "all-waste" management system. It allows the householder to effectively use all their water twice – once in the house and again for irrigating their lawns and gardens.  While a greasetrap is not required it is strongly recommended that householders stringently limit the amount of grease/oils entering the system.  Fats and oils should not be disposed of down the kitchen sink.  This continues recommendations that have been in place for sometime regardless of the type of waste disposal system installed (ie all waste or onsite treatment system).

Note:  Commercial applications may still require a dedicated greasetrap subject to the nature of the operation.

  1. Does this system have Department of Infrastructure & Planning approval for installation throughout Queensland?

Yes. Chief Executive Approval 03/2011.  Onsite sewerage treatment systems require approval under the authority of the Department of Infrastructure & Planning for installation in Qld.  Approvals are granted for 5 years, at the end of which renewal must be applied for to the relevant department.  Approval for Nature Flow Mk II STP is currently valid until January 2015. 

  1. What is a "Riser" and when is a Riser necessary?

A Riser is an extension made from concrete used to lower the invert level of the inlet to a HSTP.  A Riser is generally required when the site is flat or where the invert level is low and the drainer could have trouble gaining fall to the HSTP. A Riser may also be required if crushing in an old septic tank and the original is too deep for the inlet to the HSTP. 

  1. What is a "Site Assessment"?

A site assessment for effluent disposal is required for Local Authority (council) approval.  It is a document detailing the layout of the disposal field (whether it is surface or subsurface, size of area, hydraulic loading, diversion and/or retention mound etc).

A completed site assessment is required to enable us to provide an accurate estimate for your project.

Look here for a list of recommended site assessors in SE Qld.

  1. What do I need to know about the chlorine tablets used in my Nature Flow Budget HSTP?

Chlorine tablets are all different and the tablets used within this system are of a specific composition. 

The chlorine tablets used in your system are slow-dissolve Trichloro-S-Triazinetrione (Tri -Chlor).

If additional tablets are required contact your manufacturer/service agent to obtain the correct chlorine tablets. 

Some basic rules...

Exercise extreme caution when opening or servicing your chlorine feeder.

Do not inhale any fumes from any chemical feeder or container.

Protect your eyes, skin and clothing from chemicals at all times.

When adding the chlorine tablets do not touch the tablets. Hold the middle of the packet. Carefully split the bottom of the packet while holding it over the chlorinator container and allow the tablets to gently fall into the unit.

Avoid chemical contact – do not drop the tablets into the unit.

The chlorinator unit utilises an O'Ring located in the lid.  Take care when unscrewing the lid to ensure this O'Ring is not damaged.  When replacing the lid, grease the O'ring and ensure it it located correctly in the lid.  Avoid cross-threading the lid and damaging the O'Ring.  Do not overtighten - a locking tab is used on the lid - do not tighten past this tab.  If unsure, please do not hesitate to contact the manufacturer or your service agent.

Material Safety Data Sheet - Chlorine Tablets.

  1. What is subsidence?

Subsidence and/or ground movement is an event caused by Nature – it is unpredictable and extremely difficult to avoid.  The degree of subsidence is dependent on individual site conditions including, but not limited to, weather (prior to, during and after installation), soil type and location of installation.  It is an event not covered by warranty.

Subsidence around tanks installed in-ground may result in increased pressure on any pipework connected to the tank. Sometimes this increased pressure will result in the pipework/fitting becoming "sheared off", stretched or split (leaking) or broken.  Defects arising from subsidence are not covered by warranty.

Generally subsidence only occurs in the first instance of changed weather conditions (ie after rain) however it may occur under other circumstances. Usually after the first instance the ground (and consequently the tank and other componentry) "finds it level" and you should not experience any further problems from this phenomenon. In very reactive soils or other unstable conditions, subsidence may occur again.

Defects caused by subsidence are possible in any installation involving tankage and pipework being placed in and below ground.

Common minor defects are:

· Shearing, leaking or breakage at the poly dispersal line from the HSTP tank to irrigation.

· Shearing, leaking or breakage at the PVC pipes between the ASF and HSTP tank.

· Shearing, leaking or breakage at the stormwater pipe into the rainwater tank.

Unless otherwise agreed, all installations are for "loose" backfill only. Compacted backfill cannot be completed around concrete tanks as the uneven pressure created when backfilling will result in movement between mouldings. It is also exorbitantly expensive and will not guarantee that subsidence will not occur.  The use of sand and other bedding materials will also not guarantee the prevention of subsidence.  Often the sand will simply be pushed out of the trench or cavity by the flow of water leaving a depression that places strain on the pipework.  The best prevention of defects caused by subsidence is simply to be aware of the possibility and to maintain vigilance in ensuring depressions are "topped up" and/or breakages etc are repaired in a timely manner.


*All prices subject to change without notice.


Send mail to webmaster with questions or comments about this web site.  Copyright © 2015 Nature Flow Systems Pty Ltd atf Nature Flow Systems Trust.  Nature Flow Systems reserves the right to alter product designs and specifications without prior notification.  While every effort is made to ensure the information on this website is up-to-date, no responsibility is taken for incorrect or outdated information.  Last modified: 25-May-2015