Under-Sink Water Filter Installation in Northampton: A 3-Stage System Explained

By Jordan Lamb · Gas Safe Engineer · Northampton

A lot of people ask me whether it's worth filtering the water that comes out of their kitchen tap. In this job I fitted a 3-stage water filter under a customer's sink in Northampton, and filmed the whole thing so you can see exactly what's involved. I also handle tap and trap repairs in Northampton.

Why fit a water filter?

Tap water in the UK is treated to be safe, but it can still carry chlorine taste, limescale and fine sediment picked up on the way to your house. A filter under the sink takes that out, so the water you drink and cook with tastes cleaner. For me, a 3-stage filter is the cheapest and best way to do it properly, and it's one of the plumbing jobs I enjoy most.

What the 3 stages do

• Carbon filter: takes out chlorine and improves the taste and smell.
• RO filter: the reverse osmosis stage filters out much finer particles.
• Sediment filter: catches the last bits of sediment before the water reaches the tap.

How the install works

1. Make room under the sink. I cut a bit of the plastic back so the filter sits where the copper pipe runs, and it's easy to get to when the filters need changing.
2. Tee into the cold supply. On this job I'd already fitted a new lever-valve stopcock on a previous visit, so I teed the filter off the cold water from there.
3. Fit isolation valves. There's an isolation valve on each side of the filter, so it can be shut off for filter changes without turning off the whole house.
4. Fill it slowly. Once it's all piped up, I open the valves gently so the water works its way through all three stages.
5. Set the flow. I leave the isolation valves at about a quarter open rather than fully on. Slowing the water down through the filters gives it more time in each stage and cleaner water at the tap.
6. Leave the filter key in easy reach, so changing the filters later is quick.

The result is clear, clean drinking water straight from the tap.

How much does a water filter install cost?

Installation for this filter is around £300. The final price depends on how the pipework is set up under your sink, so I'll always take a look and give you a fixed quote before starting.

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