Modern off-mains sewage treatment systems, like GRAF UK’s One2Clean and OneAdvanced systems, are designed to run quietly and efficiently in the background of your home. Yet you might wonder what day-to-day running actually looks like and what the impact on your electricity bill and routine will be. This blog post demystifies the operation of these treatment plants by answering common questions we hear, such as “Can I turn it off at times?”, “Does it run constantly?”, “What about when I’m on holiday?”, and “Is it normal that it switches on and off?” We’ll also explain why the system is programmed to aerate for about 10.5 hours per day (typically starting at 7am and 7pm). By the end, you’ll see how GRAF UK’s sewage treatment systems keep your wastewater safely treated with minimal power consumption. Smaller domestic systems, like the One2Clean, typically use around 0.6 kWh per day (about the same as a light bulb), while larger units will use incrementally more energy in line with their capacity.
How Do One2Clean and OneAdvanced Operate Each Day?
Both the One2Clean and OneAdvanced systems use a process called a sequencing batch reactor (SBR) to treat wastewater in cycles rather than continuously. In simple terms, the treatment happens in phases: first, incoming sewage is collected and allowed to settle; next, an aeration phase injects oxygen into the water to enable beneficial bacteria to break down pollutants; then the water is allowed to settle again so that clean effluent can be drawn off. In larger commercial SBR systems such as the OneAdvanced, any remaining sludge is then returned to the primary chamber as part of the cycle. In the smaller One2Clean domestic system, this step isn’t required, the process is intentionally streamlined for straightforward household use. This entire cycle repeats periodically throughout the day. Importantly, the air compressor (which delivers oxygen to the bacteria) does not run 24/7 it operates intermittently under the control of the system’s panel. In fact, One2Clean’s compressor typically runs only about 10 and a half hours per day in total, instead of continuously, which cuts energy usage by roughly 50% compared to many older treatment systems that run non-stop. GRAF’s smart control technology supplies power to the aerator and valves at specific intervals, optimising the biological process without wasting electricity.
For One2Clean owners, this means the unit is usually programmed to run a morning and evening treatment cycle, often around 7am and 7pm, totalling ~10.5 hours of aeration per day. This schedule aligns with typical household water usage patterns (after overnight and again after the daytime) to efficiently process each “batch” of wastewater. Between these active periods, the system is in a settling or idle phase, effectively “pausing” the air blower, so don’t be surprised if you don’t hear it humming at all times. The entire process is managed automatically by the control panel, so no manual intervention is needed during normal daily operation.
Despite the sophisticated control, the design remains homeowner-friendly and robust. There are no moving mechanical parts inside the tank itself, and no submerged electrical gadgets that could fail. All the crucial components (the air pump compressor and the electronic control panel) are located externally or in a dedicated housing, making maintenance easy and keeping the risk of internal faults low. The systems are also built with sound insulation in mind, the standard air compressors operate from as little as 36 decibels. In other words, noise from the unit is minimal, and many owners find it unnoticeable in day-to-day life. (For additional peace of mind, you can install the compressor in an outdoor cabinet or outbuilding, an option that further muffles any sound and vibration.) In summary, One2Clean and OneAdvanced quietly go about their business on a pre-set cycle, using very little energy and ensuring your wastewater is treated to a high standard with minimal fuss.
Can I Turn My Treatment Plant Off at Times?
It’s a common question: “If no one is using water for a while (say, overnight), can I switch the system off to save power?” The answer is no, you should keep the system powered on and let it run as designed. Even though the compressor isn’t running constantly, the control panel needs to execute the timed cycles each day to maintain the health of the system. The treatment plant relies on a living ecosystem of bacteria to break down waste, and those microbes need regular oxygenation and circulation. Turning off the system for extended periods (even just at night) is not recommended, because without intermittent aeration the bacteria could starve of oxygen, the tank could turn septic, and treatment performance would drop off. We explicitly advise that continuous operation (via the automated on/off cycles) is critical for the biological process to work effectively.
Furthermore, the energy savings from manually shutting the system down would be negligible remember, the One2Clean energy usage start from 0.63 kWh per day. That’s roughly the consumption of an 8-watt LED light bulb running 24 hours. In financial terms, that’s well under £1 of electricity per week for most UK households, so there’s little to gain by trying to micromanage its on/off times. The system is engineered to be as efficient as possible by default, so you can “set it and forget it.” In fact, stopping and starting the plant could do more harm than good. If the aeration is halted for too long, waste in the tank isn’t being biologically processed and could produce odours or even cause the effluent quality to fall below regulatory standards. And when power is restored, the system may need time to ramp back up to optimal treatment. In short, leave your wastewater treatment plant running, it’s safest and best to let the automated cycles do their job of keeping your water clean and your tank healthy.
Is the Compressor Supposed to Run Constantly?
No, the compressor in a One2Clean or OneAdvanced plant is not running 24/7 and that’s by design. These systems use an intermittent aeration schedule, so it is entirely normal to hear the blower motor turn on and off throughout the day. Many new owners are initially concerned when they realise the unit isn’t making a noise all the time or see that it “goes to sleep” periodically. Rest assured, this on/off cycling is exactly how the plant achieves its efficiency. The controller will activate the air pump during the aeration portions of the cycle (for example, for a few hours after 7am and after 7pm), then turn it off during settling phases when aeration isn’t needed. Over a 24-hour period, the compressor is only active for roughly 10.5 hours total (it may be slightly more or less, in the ~8–12 hour range depending on the model and settings). This clever duty cycle is how GRAF systems slash energy consumption by up to 50% relative to older units that ran air pumps non-stop.
So if you notice the hum of the compressor stopping for several hours and then restarting later, that indicates the system is following its programmed sequence correctly. In fact, the pause is when the tank is in a settling or clarification stage, during that time, the wastewater that was just aerated is sitting undisturbed, allowing solids to separate out and the clarified water to rise to the top for discharge. Once that stage is complete, the controller will kick the compressor on again to begin a new treatment batch. This cyclical operation not only saves power but also reduces wear and tear on the compressor (since it’s not running full-time). One side benefit is a longer service life for the air pump, the most significant mechanical component in the system, which can defer replacement costs. It also means less noise on the whole. Even though the unit is quiet, it’s nice to know it won’t be humming away all night; instead, it works in bursts and then stays silent for extended periods. You should only be concerned if the compressor never comes on (or conversely, if it never seems to turn off), as that could indicate a fault, otherwise, periodic on/off operation is the normal and expected behaviour.
Can I Adjust the Aeration Timing (e.g. Only Run it Overnight)?
Some homeowners ask if it’s possible or advisable to change the factory-set schedule for instance, to have aeration occur only overnight (perhaps to capitalise on off-peak electricity rates or to avoid any daytime noise whatsoever). In general, it’s best to stick with the default programming provided by GRAF unless you have a specific need and the change is supported by the manufacturer. The One2Clean and OneAdvanced controllers are pre-configured to optimise treatment based on typical daily flow patterns. Running one cycle in the morning and one in the evening ensures that incoming sewage doesn’t sit too long without treatment and that the bacteria get oxygen at appropriate intervals. If you were to aerate only at night, then all the wastewater produced in the daytime would sit untended until the evening, which could lead to septicity or odour issues, especially in warmer weather. GRAF’s guidance is that turning the system off during part of the day (whether night or day) is not recommended, because continuous daily operation is key to performance.
From a technical standpoint, the control panel does allow some customisation on advanced systems, for example, the OneAdvanced models have a “holiday mode” and can be calibrated for under-loading. Those features are intended for scenarios like long periods of very low usage (such as a holiday home that’s empty for weeks), and they adjust the runtime or dosing to keep the biology stable. However, they are not simply shifting all aeration to night hours; instead, they might reduce the frequency or duration of cycles if the system senses little inflow. For a normal primary residence, such tweaks are usually unnecessary. The standard 10.5-hour/day cycle is already energy-efficient and costs only a few pence per day to run, so there’s little economic benefit to forcing it into an overnight-only pattern. Noise shouldn’t be a deterrent to daytime operation as noted, the units are whisper-quiet (around 36 dB), and you can situate the compressor away from living areas if you wish. Many owners place the compressor in a garage, utility room, or garden shed, and report that it’s virtually inaudible.
Can I Leave the System Running While I’m on Holiday?
Yes, in fact, you should. One of the great advantages of a modern sewage treatment plant is that it can run autonomously with very little supervision. If you’re going away for a couple of weeks (or even longer), you do not need to turn off or adjust your One2Clean/OneAdvanced system. Keep it powered on and let it continue its normal cycles. The energy usage is so low that it will barely make a dent in your electricity bill while you’re gone, the consumption is comparable to leaving a single light bulb on. More importantly, allowing it to run ensures that the bacterial culture in the tank stays alive and healthy. Even if no new wastewater is entering the system (because no one’s home using the water), the controller will still periodically aerate the water in the tank, which keeps the microbes active and the water fresh.
GRAF UK explicitly advises that for typical domestic situations, leaving the system running during holidays is the right approach. There’s no need for a “pause” button, the plant self-regulates and will simply treat whatever small amount of waste is in there. When you return and normal flow resumes, the bacteria will already be in good shape to handle it. On the other hand, if you were to turn the system off while away, the stagnant conditions could cause the biology to go dormant or die off, leading to bad odours and poor treatment when restarted. It could take some time for the system to re-establish equilibrium. Thus, avoiding that scenario is as easy as just leaving it be.
For larger or advanced installations (for example, commercial sites or very large residential systems), there is often a “holiday mode” feature in the control panel. This doesn’t shut the system off, but it can dial back the aeration a bit to save energy when extended low-use periods are anticipated. In advanced systems, there are even options for automatic carbon dosing to feed the bacteria if the normal sewage flow (their food source) stops for a long time, a consideration for holiday homes or seasonal properties. However, these features are generally not something the homeowner needs to tinker with; if your system has such capability and you plan to leave it unused for months, you could ask your maintenance provider about activating a low-load setting. For the typical homeowner going on a holiday for a few weeks, no action is required except maybe to ensure the system is in good order before you go (it’s always a good idea to keep up with yearly service and desludging schedules). You can jet off knowing your treatment plant will keep calmly doing its job, protecting the environment in your absence.
Seasonal Considerations
One concern UK users may have is how the changing seasons might affect their sewage treatment plant’s operation. The good news is that One2Clean and OneAdvanced are designed to handle year-round UK climate conditions with ease. The system is buried underground, which naturally insulates it from extreme cold. In winter, even if air temperatures drop below freezing, the water in the tank typically remains well above 0 °C, partly due to the warmth of incoming household water and partly due to the earth’s insulation. The bacteria in the plant do slow down a bit in cold temperatures, but as long as the water stays above about 12 °C, they remain effective. (For context, 12 °C is a temperature threshold often cited for optimal biological activity. If the water were to get near freezing, the treatment process would be severely hindered, but under normal UK conditions this is extremely unlikely, especially if the tank is installed at the proper depth.) In fact, the performance tests for these systems are conducted at ≥12 °C to mirror typical conditions and ensure they meet standards year-round. If you live in an area prone to very hard frosts and are concerned, you can ask your installer about adding insulation or installing the tank a bit deeper for extra protection, but for most homeowners, this isn’t necessary.
During hotter weather in summer, the biological activity can actually increase slightly (since warmth boosts bacterial metabolism), and the system will continue to operate normally. The main thing in summer is to maintain normal usage patterns; if you’re home and using water, the plant is doing its job. If you go on extended summer holidays, refer to the guidance above (the system can handle it). Very heavy rainfall isn’t a direct issue for the treatment plant itself, remember, it’s a sealed system, so rainwater should not be entering the tank (any surface water should be kept out, and roof/yard drains should bypass the sewage treatment unit). However, seasonally high groundwater or prolonged wet weather can impact your soakaway or drainage field (where the treated effluent is released). In winter when the ground is saturated or during flooding conditions, drainage fields percolate more slowly. This is something to be mindful of, but as long as your drainage field was properly designed to regulations, it should cope with normal British rainfall patterns. The output from a One2Clean/OneAdvanced is very clean, well within the standards for discharge to a soakaway or watercourse, which helps ensure you’re not causing pollution even in difficult conditions. Just make sure regular maintenance is done (e.g. sludge is emptied annually) so that the high effluent quality is maintained; this gives you the most buffer in any situation.
If you have a seasonal property (say a countryside cottage that’s only occupied part of the year), GRAF’s advanced options can accommodate that. As noted, the OneAdvanced system can be outfitted with under-load calibration or carbon dosing modules for periods of low use. These keep the biology ticking over when there’s not much “food” (sewage) coming in, so that when you do occupy the house again, the treatment plant ramps up quickly. In normal residential use, though, you typically won’t notice any seasonal difference the system will quietly adjust as needed. No manual seasonal adjustments are required on your part. Just continue to operate the plant as instructed, and it will handle cold snaps, heat waves, and everything in between.
One seasonal tip: after a very long dry spell (or if a property was left unused over a season), you might run some water and flush toilets when you return just to refresh the tank. The incoming flow will re-wet all the components and give the bacteria new nutrients, essentially “waking” the system up if it had a sleepy period. But again, the control system likely was still aerating occasionally even if no new wastewater came in, so things should be in good shape. The bottom line is that One2Clean and OneAdvanced are built for UK weather and usage patterns. They offer reliable, year-round operation without needing any seasonal mode changes, making them very user-friendly.
Efficient, Worry-Free Operation All Year Round
Owning a GRAF One2Clean or OneAdvanced sewage treatment plant means you have an eco-friendly, low-maintenance solution managing your wastewater behind the scenes. As we’ve covered, you do not need to tinker with it daily, in fact, it’s best to let it run exactly as it’s programmed. The system’s roughly 10.5-hours-per-day aeration cycle is optimised for performance and efficiency, keeping power usage to a minimum (around 0.59–0.63 kWh per day on a small domestic unit) while still delivering top-notch treatment results. You can’t really improve on this by shutting it off or changing the times, so just trust the process!
Remember that it’s normal for the compressor to turn on and off periodically; that’s a sign of the intelligent SBR process at work, not a malfunction. Leave the system running even when you’re away, since it’s content to quietly look after itself and will be ready when you need it. With no moving parts inside the tank and very low noise levels, these GRAF systems are designed to blend into your home life, you get peace of mind that your household’s wastewater is being treated safely and legally, without a hefty energy bill or constant upkeep. All you need to do is arrange the routine annual service and desludging, much like servicing a boiler or car, and the plant will do the rest.
In essence, the One2Clean and OneAdvanced make sewage treatment “set it and forget it” for homeowners, delivering reliable performance for the long term. We hope this article has answered your questions and put to rest any worries about day-to-day operation. If you’re considering one of these systems for your property or have more questions about their use, feel free to reach out to our team at GRAF UK. We’re always happy to help you understand how our products can fit your needs and keep your home sustainable and compliant.
Posted by Callum Vallance-Poole, on October 6, 2025.
