iSPA-T or iSPS-X? Choosing Between AQUAIOT’s Two Multi-Parameter Water Quality Systems
TL;DR: The iSPA-T is a complete online monitoring station: it measures chlorine, COD, TOC, turbidity, pH, conductivity and temperature, sends data over 4G and can support closed-loop control of a pump room. The iSPS-X is a compact instrument that takes up to four reagent-free sensors, from dissolved oxygen to ammonia and nitrate, in an IP68 housing with an RS485 output. Treated water and chlorine usually point to the iSPA-T. Raw water, rivers and effluent usually point to the iSPS-X.
Last updated: 30 September 2026
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Key takeaways
- The iSPA-T measures COD, TOC, turbidity, free or total chlorine, pH, conductivity and temperature in one online system.
- The iSPS-X takes up to four sensors covering parameters such as pH or ORP, conductivity, salinity, dissolved oxygen, turbidity, COD, TOC, ammonia and nitrate.
- Only the iSPA-T measures free and total chlorine, using constant voltage, membrane-covered or DPD methods.
- The iSPS-X uses no reagents, is rated IP68 and outputs over RS485.
- Both systems can complete a measurement cycle in as little as 10 seconds.
- Drinking water regulations set turbidity at 4 NTU and nitrate at 50 mg/l at consumers’ taps, two of the parameters these systems watch.
What is the difference between the iSPA-T and the iSPS-X?
The iSPA-T is a complete online monitoring system: sensing, control, 4G communication and cloud connection in one station, with thresholds, alarms and the option of closed-loop control of pump room operations. The iSPS-X is a measurement instrument: a compact housing that takes up to four sensors and passes their readings over RS485 to a data platform or handheld terminal.
Put simply, one is a finished monitoring point and the other is a flexible sensor head. The station suits a site that wants one self-contained station on a treated water line. The iSPS-X suits a site that wants to choose its own set of up to four parameters and connect them into an existing telemetry or SCADA system.
Both come from the same product family and share a quick measurement cycle, as short as 10 seconds, and both are used on the same kinds of site: treatment works inlets and outlets, treatment processes, pipe networks, surface water and groundwater, and industrial water.
Which parameters does each system measure?
The iSPA-T measures COD, TOC, turbidity, free or total chlorine, pH, conductivity and water temperature, with further parameters added to suit the site. The iSPS-X can take sensors for pH or ORP, conductivity, salinity, dissolved oxygen, turbidity, COD, TOC, ammonia nitrogen, nitrate nitrogen and temperature, up to four at a time.
The lists overlap on the organic load and clarity parameters. Total organic carbon is a non-specific indicator of water quality, chemical oxygen demand is a quick way to quantify the organics in water, and turbidity tracks suspended material. Both systems can watch those.
They split on the rest. The iSPA-T adds chlorine, the parameter that matters most in treated and distributed water. The iSPS-X adds dissolved oxygen, ammonia and nitrate, the parameters that matter most in effluent, rivers and groundwater.
| Parameter | iSPA-T | iSPS-X |
|---|---|---|
| Free or total chlorine | Yes | No |
| COD and TOC | Yes | Yes |
| Turbidity | Yes | Yes |
| pH and conductivity | Yes | Yes |
| Dissolved oxygen | Not in the standard set | Yes |
| Ammonia and nitrate | Not in the standard set | Yes |
| Salinity and ORP | Not in the standard set | Yes |
Which one measures chlorine?
Only the iSPA-T measures free and total chlorine. It supports three methods: constant voltage, membrane-covered sensors, and DPD, a colorimetric method. That makes the station the choice wherever the job is to confirm disinfection, such as a treated water reservoir outlet, a booster station or a private supply.
Chlorine is the reason most treated water sites choose the online station. A falling residual is an early sign that disinfection is not holding through the network, and a rising one can point to a dosing fault. Watching it every few seconds, with an alarm threshold, replaces the occasional manual grab sample.
Where chlorine is all a site needs, a dedicated analyser may be enough. Our guide to the free and total chlorine analyser covers that option.
Which one suits effluent, rivers and groundwater?
The iSPS-X usually suits effluent, rivers and groundwater, because those jobs call for dissolved oxygen, ammonia and nitrate, and because its sensors sit in harsh water for long periods. It uses no reagents, carries an IP68 rating and comes with a cleaning brush on the sensor for a long maintenance-free cycle.
Nitrate is a good example of why the parameter choice matters. The Water Supply (Water Quality) Regulations 2016 set nitrate at 50 mg NO3 per litre at consumers’ taps, and turbidity at 4 NTU. Rising nitrate in a borehole or a river intake is worth seeing weeks before it reaches a treatment works.
How do they connect and alarm?
The online station connects over 4G straight to a cloud platform, where each parameter has a user-defined threshold that triggers an alarm, and it can feed back to pump room controls for closed-loop operation. The iSPS-X outputs over RS485, so its readings go to a data acquisition platform, a telemetry unit or a handheld terminal on site.
That difference often decides the choice on its own. A remote reservoir outlet with no network nearby suits a station that brings its own 4G. A treatment works with an existing SCADA system suits an instrument that plugs into it. Either way, readings can reach the AQUAIOT Cloud for alarms, trendlines and exports.
How much maintenance do they need?
Both systems are built for long unattended runs. The station has a self-cleaning module for long-term maintenance-free operation. The iSPS-X uses no reagents, which removes reagent top-ups, and its sensors come with a cleaning brush. The DPD chlorine method is the one option in either system that uses a reagent.
Maintenance still matters. Sensors drift and foul, so the schedule for checks and calibration should be agreed at the start and tied to the alarm history, so that a sensor that starts behaving oddly is looked at before its readings are relied on.
Which system should you choose?
Choose the iSPA-T for treated or distributed water where chlorine must be watched and a self-contained 4G station suits the site. Choose the iSPS-X for raw water, effluent, rivers or groundwater where dissolved oxygen, ammonia or nitrate matter and the readings need to join an existing telemetry or SCADA system.
- Do you need chlorine? If yes, the iSPA-T.
- Do you need dissolved oxygen, ammonia or nitrate? If yes, the iSPS-X.
- Is there a network to join? SCADA or a data platform on site favours the iSPS-X; a remote point with nothing nearby favours the iSPA-T and its 4G.
- Can reagents be topped up? If not, avoid the DPD option, or choose the reagent-free iSPS-X.
Our water quality monitoring service covers survey, installation and dashboards for either system.
Frequently asked questions
What is the iSPA-T?
The iSPA-T is AQUAIOT’s multi-parameter water quality online monitoring system. It measures COD, TOC, turbidity, free or total chlorine, pH, conductivity and temperature, sends data over 4G, alarms on user-defined thresholds and can support closed-loop control of pump room operations.
What is the iSPS-X?
The iSPS-X is a multi-parameter water quality measurement instrument that takes up to four sensors, such as pH or ORP, conductivity, dissolved oxygen, turbidity, ammonia or nitrate. It uses no reagents, is rated IP68 and outputs over RS485 to a data platform or handheld terminal.
Which system measures dissolved oxygen?
The iSPS-X takes a dissolved oxygen sensor as one of its four positions, which makes it the usual choice for effluent, rivers and aeration processes. The iSPA-T can add optional parameters, but its standard set focuses on treated water, including chlorine.
How often do they take a reading?
Both the iSPA-T and the iSPS-X can complete a measurement cycle in as little as 10 seconds, so a change in water quality shows within moments rather than at the next grab sample.
Where to start
Start with the question the readings must answer: is disinfection holding, or is something entering the water that should not? That usually points to one system before the specification sheets are opened.
To choose between them for your site, tell us about the water you need to watch and a UK engineer will come back within one working day. See also our guide to the multi-parameter water quality monitoring system.