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Unit Sizing

When sizing a Hybrid Toilet unit, refer primarily to the Hybrid Unit size calculator below. This is the most accurate method of calculating unit sizing.  All unit sizing should be done in conjunction with trained Hybrid Toilet representatives. The average person is not qualified to size waste treatment units.  Each individual site must be assessed on its on merits, looking closely at the circumstances that surround that particular site only. There is no such thing as a generic sized unit.

Never under any circumstances take a yearly average figure and size the unit based on that information alone.

Things to Consider

Factors that must be considered when sizing a unit are the type of the clientele using the unit, the type of use of the system (eg. day use area, camping area and combined use) and fluctuations in loading and temperature. The travel distance from staging points has a bearing on use rates as well.

Growth Rate Allowance

Something that is mostly forgotten about or is not considered is the growth rate that may occur on the unit loading. Hybrid Toilet units, properly installed, will last for decades. Some areas like the World Heritage area of Fraser Island in Queensland are undergoing growth rates of around 5% per year. When this is calculated out over time, the effect can be substantial. It may be appropriate to allow for, say, 10 years of growth and plan for additional systems or upgrades as you approach that length of time.

Capped Visitor Numbers

Where circumstances allow, it is ideal if visitor numbers can be capped. Controlled visitor numbers allow for more accurate unit size calculations to occur. If this is the case, then there is no need to build in percentage growth figures. Capped visitor numbers allow planning for minimal impact on the site.

Door Counters

The utilisation of door counter systems allows the tracking of unit usage rates. These figures can be recorded on data bases and analysed against unit performance.

Unknowns Allowance

All the above points have potentially a significant bearing on the unit's performance. It is prudent to allow for around 25% extra capacity when calculating a rating. The Hybrid Calculator does this automatically. This gives an allowance for unknowns.

Unit Size Driver

If you have a particular period of the year where visitor numbers peak for a couple of months, work on these figures only and discount the remainder. This is particularly important as under sizing the unit capacity at the beginning can create long-term management and environmental problems. Large short duration spikes measured in a couple of days only will have little effect. It does become significant when the loading stretches out past this period. Ideally, with a little forward planning, Porta-Loos or the like should be brought in to carry significant spikes for once off events. Decisions on unit sizing based on cost alone initially may seem prudent, but in the long term, the cost of an under capacity system will far outweigh the presumed initial cost saving.

The Hybrid Toilet System Calculator v1.1

The below calculator is only compatible with Internet Explorer.

Date: 26/05/2019
Job Name / Number:
System Designer:
Sales Agent:
If the location experiences extreme conditions, eg. alpine or desert, please contact you agent for site specific advice.

Estimated uses per 24hr period
(actual door count data)

Number of campers staying overnight
(using toilet approx. 3.5 times each)
Number of day visitors
(using toilet approx. 2 times each)
If you do not have reliable estimates for usage, we recommend using a door counter system
(Battery or PLC) on any current amenities to more accurately establish usage figures.
What is the expected growth in number of users per year?
eg. Fraser Island experiences ~ 5% growth in usage per year.
How long must this system cater for the calculated load?
A second system may be required for example, after ten years.
Actual calculated load
The appropriate system size for this calculation is…
Systems greater than 150 Person may require special design. Systems greater than 300 Person require site specific design by manufacturer. Please contact your Distributor for more information.

The maximum design flow rate for this size unit is as follows…  
When installing MicroFlush Pedestals
When installing NonFlush Pedestals

Calculations for holding tank systems (not flow to ground option)
Maximum desired period between pump-outs
Average period is 30 days

The minimum size of holding tank required will be:
Note: Large systems may require multiple tanks or more frequent pump outs    

If the site has effluent discharge restrictions such as in World Heritage areas, you may need to consider a holding tank, or other options. For details on these systems, please contact your Agent.

Please contact your nearest Distributor to confirm sizing and inquire about pricing.