The real dimensions, an honest look at old tank systems, and why your press under the sink is safe
You have done the research. You know reverse osmosis is the gold standard for drinking water at home. Then you open the press under your sink, look at the waste pipe, the bin and the mystery bag of bags, and one question stops everything: where exactly is this thing supposed to go?
It is the most common doubt we hear from people who are otherwise ready to sort their drinking water. And it is a fair one. Ask most people to picture a reverse osmosis system and they see a cluster of tubes, three or four filter housings and a bulky storage tank eating the entire cupboard. Search for photos online and that is largely what comes up, because that is what these systems looked like for decades.
The good news is that the picture is about twenty years out of date. Here is what a modern system actually measures, how that compares to the traditional tank equipment that created the worry in the first place, and what installation really involves.
Why traditional RO systems take up so much room
Traditional reverse osmosis systems rely on a pressurised storage tank. The old membranes produced water slowly, drop by drop, so the system filled a tank in advance and you drew your glass from that. The tank alone is often the size of a small keg. Add three or four separate filter housings bolted to a bracket, the pipework connecting it all, and the clearance you need to change filters, and the whole press under the sink is usually gone.
The tank brings other headaches too. It holds a few litres at most, so it can run out mid pot of pasta and leave you waiting while it refills. And because filtered water sits in it for hours, the tank itself needs sanitising as part of maintenance.
So if you have been hesitating because you pictured all of that under your sink, your instinct was right. It just applies to the old generation of equipment.
Our reverse osmosis system, measured
Our answer to this problem is the ArkkZ Reverse Osmosis System, and here are its real dimensions, straight from the spec sheet: 39cm long, 13.5cm wide, 39.5cm high.
To make that concrete, the ArkkZ is about the size of a box of printer paper stood on its side. Its slim 13.5cm width means it slots neatly against the side wall of the cabinet, leaving the floor of the press free for the bin and the washing up liquid.
Real Life with Arkkz
There is some pictures about how your sink looks like having our reverse osmosis system.
Honest comparison
Traditional reverse osmosis systems deserve credit, because for decades they were the only way to get purified water at home and they still do the core job well. They also tend to cost less upfront, and since the tank does the work, most of them run well. But that tank is where the compromises live. It swallows most of the press under your sink, it holds a few litres at most so it can run out mid pot of pasta, and because filtered water sits in it for hours it needs regular sanitising to stay hygienic.
The ArkkZ takes a different approach. It is a tankless, direct flow system, so water is filtered fresh at up to 2 litres per minute the moment you open the tap. That means no stored water, no tank maintenance, and a unit just 13.5cm wide that uses up to 70 percent less space. You get a system that never runs dry and a press you can still use for everything else.
What installation day actually looks like
This is the other half of the worry. People imagine days of plumbing work, a torn apart kitchen and a hunt for a reliable installer.
Here is how it works with us. Installation is included in the price, and it is carried out by our own trained Renewell Water technicians, not a subcontractor you have never heard of. We cover every county in Ireland and Northern Ireland. After you order, our team contacts you to book a day and time that suits, the technician fits the ArkkZ and your new drinking water tap, tests everything, and shows you how it all works before leaving. For most homes it is done in a single visit, and the only visible change in your kitchen is an elegant new tap beside your existing one.
There is nothing for you to measure, source or figure out. If anything about your kitchen is unusual, the technician deals with it on the day. That is the point of doing our own installations: the person fitting your system has done it hundreds of times in kitchens exactly like yours.
Simon Newell, our founder, has been saying the same thing for over two decades: "Buy the filter, don't be the filter." The only thing that should stand between your family and better water is a booking, not a measuring tape.
The short answer
Yes, it fits. A modern tankless reverse osmosis system is slimmer than a cereal box is wide, and the ArkkZ was engineered specifically for real Irish and UK kitchens. That focus on real homes is a big part of why we are the number one rated water company in Ireland, with over 20,000 homes using our systems. You can read what those homeowners say about their installations on our reviews page.
In fact, the ArkkZ leaves so much of the press free that plenty of our customers fit an entire Duo Package under the one sink, the ArkkZ plus our compact Green Softener, and still close the door with room to spare.
Ready to stop worrying about space? The ArkkZ Water Filtration System comes with your tap, full professional installation and nationwide coverage all included.