Have a question about your UV disinfection unit? Unsure which UV lamp you require? Below are some of our most frequently asked questions.
Can’t find the information you need? Contact us today.
Will a UV unit filter my water?
Not unless your water supply is contaminated with tennis balls. A UV unit offers absolutely no filtration what so ever. The term “UV filter” is a bit of a personal annoyance. A UV disinfection system will often come with filtration options but the UV unit itself has no integrated filtration.
Can I shut off my UV unit?
Yes you can but we wouldn’t recommend it. UV lamps are manufactured to be left on 24/7 for one whole year. If the UV lamp is switched off, then bacteria can migrate through the chamber so the next time you turn the tap on, untreated water will come out. As well as that, the filaments in UV lamps are weak so they will become damaged very quickly being turned on and off a lot.
How long will a UV lamp last for?
Typically 9,000 hours or 1 year. After this, the UV lamp will still be on (you can still see the blue light) but it won’t give out an appropriate UV dose. Some UV lamps using newer technology will last 2 for years now. These are usually used for bigger applications though.
Do I need a Pre-filter?
We recommend you do use a pre-filter to protect the UV unit. Without a pre-filter, quartz fouling is more likely as is UV shadowing. For drinking water you should be looking at using a 5 − 25μ filter cartridge with it.
What is UV shadowing?
UV Shadowing is when small bacteria hide inside larger particles that pass through the UV unit. Because they’re inside the large particle and UV can’t penetrate solids, the bacteria are protected from treatment. We counter this with filtration.
How often will a UV filter cartridge need replacing?
Usually between 2-6 months. The way you can tell is when you notice a drop in water pressure, this means your UV filter is clogged up and needs changing. How quick for your particular filter depends on where you are in the country, where your water comes from and how much water you use.
What do Micron (μ) ratings mean?
Where a human hair is around 80μ (microns) and a single grain of talc is around 5μ, we can see down to 40μ, assuming you have 20/20 vision. Many manufacturers claim their UV units work optimally with a 5μ pre-filter. In our experience these block up far too quickly and from a practical view point achieve little more than a 20-25μ pre-filter. Of course, if you really want to you could buy 5μ replacement cartridges but they will block up more quickly!
Is my UV unit working?
Different UV units will have different ways to tell you if they’re working or not. It could be anything from a green light on the lamp connector to the fault code on a ballast display. If you’re unsure whether your UV is working, contact us and we’ll try to help.
What UV unit do I need?
Several important factors come into play that mean you have very little choice in what unit you need. You need the one you need. By using the UV Transmittance ‘T10’ value of your untreated water (T10 is a measure of UV treatability or ‘how well does UV penetrate through my particular water’) and finding out the maximum flow rate passing through the UV disinfection system at any one time, we can choose a unit that will give the appropriate level of treatment.
How effective is UV Disinfection?
UV disinfection is 99.99% effective i.e. 1 out of every 10,000 bacteria that pass through the UV unit may remain intact after UV treatment. In reality, the performance of a UV unit is usually even better than this although it’s only been scientifically proven to this level.
How do I clean my quartz (inc. Sensor window if a UV sensor is fitted)
The correct way to clean quartz is using an acid based cleaning product (natural ones included like vinegar or citric acid) with a mildly abrasive cloth (we use those green plastic kitchen scouring pads, you know the ones). Do not use anything that may scratch the surface of the quartz.
What does UV light do?
UV light breaks down DNA and makes bacteria unable to split or reproduce. Although the bacteria aren’t actually dead after UV interaction, most tend to live for only a few minutes and are harmless while they are. For a more detailed explanation on how UV works, I’ve blogged about this as well so you can check it out there.
How effective is UV against bacteria?
Different bacteria have different levels of resistance against UV light. Our UV units give an average dose of 30mJ/cm2 so comparing that against what it takes to neutralise some bacteria you can see how effective it is.
- Legionella pheumophilia 12.3 mJ/cm2
- E.coli 6.6 mJ/cm2
- Cryptosporidium 12 mJ/cm2
- Anthrax 46.2 mJ/cm2
What do Sterilight ballast fault codes mean?
- Blank screen – No power / lamp failure mode
- Low UV Level – Test water supply / clean quartz sleeve and sensor window
- A2 – UV level below 50% and the alarm has been muted
- A3 – Lamp life expired / day counter at 0 / replace UV lamp
I’ve changed my Sterilight lamp and the alarm’s still sounding.
After you replace your UV lamp you need to reset the ballast to get the day reading back to 365. If you don’t, the alarm will keep beeping at you. You can reset the ballast by turning the power off from the mains, holding in the reset button( small button located on the end of the controller), then turning the power back on and waiting for the RSET code to display. This may take 5 – 7 seconds whilst still holding the button in but then hey presto!
Where do I put my UV unit?
You want your UV unit as close to the point of use as conveniently possible. If you have a small UV unit for your kitchen tap, then the UV system should be under the kitchen sink. If it’s treating multiple outlets then you want it as close to where the pipe work branches off as possible. If you are treating a typical whole house and you have a storage tank for all of the cold water, put it on the outlet side of the water storage tank. That way, all of the water coming out of the tank to the cold supply will be treated.
What are the benefits of UV disinfection vs. alternative water treatments?
The main alternative to UV is chlorine treatment. While initial setups are similar in cost, UV costs less to maintain on a yearly basis, it doesn’t need the secure storage and handling that chlorine demands (because of its toxicity) and you don’t need to take regular level readings of UV because you can’t overdose with it. The main one is that UV is easy to use and maintain.
How is UV dose measured?
UV Dose = UV intensity x Residence time. This means UV dose is affected by the lamp output and the time that the water is exposed to the UV light for. So, if the lamp is too old then the output will be too low or, if the water flow rate is too high (reducing residence time) then the dosage given by your UV unit will be too low. If you have both of these scenarios then sort your system out!
How easy is it to install a Domestic UV unit?
It’s as easy or as hard as any other minor home plumbing job. It’s taking out a section of pipe work and putting the UV system in its place (with a suitable pre-filter if required), that being simple or hard is up to you. If in doubt, give your local plumber a call.
What will affect the UV unit treating my supply?
In an urban environment, not a lot should go wrong (famous last words). You’re not likely to get a slug of dirty water coming through your mains supply. In a rural situation where your water may be coming from a spring or borehole, many things can affect the UV unit. If the supply is open then you can get all sorts falling in. Seasonal changes also affect the water quality and also ‘nasties’ can leach from the surrounding substrate. From a UV’s perspective, the worst addition to the water would be from dissolved iron and manganese. If these are present then our lives are made harder due to them and we need to take special precautions.