How to Fit an Under-Sink Water Filter in Your Caravan
So, today we’re fitting a water filter into our caravan. The one we went with goes underneath the sink, and that then gives us filtered water to the tap in our kitchen.
Even though we always put filtered water into our tanks whenever we’re filling them up, we thought another layer of protection was worth having. The water that comes out of the tank basically gets filtered twice, so that means it should be pretty good drinking quality. And while we had the cupboard open, Tim also tidied up the water hoses under there so we got a bit of storage space back.
– For all your caravan fittings and water gear: Caravan RV Camping
Why We Only Filter the Kitchen Tap
We decided to go with one that sits underneath the sink and only does that tap. We sort of thought there’s no real point in filtering the water to the shower, the hand basin, or the tap on the front of the A-frame. Just the one we use for drinking water. So that sort of makes sense.
The filter itself is only half of it for us. We always run our water through an inline filter when we fill the tanks, and this under-sink unit is the second layer on top of that, right where we drink from.
If you want the bigger picture of where the water goes from the tank to the tap, we’ve covered that in How does a caravan water system work?
What to Look for in an Under-Sink Water Filter
The one we’ve got is a filter with a slightly higher flow rate than some of the other filters, like your pure taps and things like that. One of the advantages of that is when you turn your water on, what comes out of the tap is not so slow. When you’re filling up that pot of water to do your cooking, it doesn’t take as long to fill up your pot.
The other thing is the fittings it comes with. It comes with all the John Guest fittings, and they’re the 12mm hose John Guest fittings, which are exactly the same as what’s currently on the van. I think that’s pretty well an industry standard. So fitting it in should be a whole lot easier, and you don’t have to use any converters to go from one size hose to another.
Now, this one we actually got off Marketplace. It was one we were looking around for anyway, and someone had one still in the box, never even used. They were going to get around to fitting it and never did. So yeah, we got ourselves a bargain. We’re not affiliated with that brand, but keep an eye on Marketplace. If you’d rather buy one new, a similar under-sink unit with 12mm John Guest fittings is the Shurflo RV and Marine Water Filtration Kit.
Before You Start: Get the Water Out of the Lines
Let’s get stuck into it. The first thing to do, before anything else, is get all the water out of the water lines.
- Turn off the water pump.
- Once the pump’s off, open up the tap and let all the pressure out.
- Once that stops running, you know you can get stuck into it.
Next, get access to the area. Our sink doors have a quick release system, so we could take them off, which makes it a lot easier. The workspace under there is still pretty tight.
Even though you’ve purged the water by opening the taps, there will still be a little bit left in the lines. Put a towel down to soak it up, and put a pot underneath where you’ll be opening the pipes, so whatever’s left in the hoses goes into the pot and hopefully doesn’t make a big old mess.
The Plan: Filter Both the City Water and the Tank Water
These John Guest fittings are pretty easy. There’s a little collet you push in, and the pipe slides out. As long as the O-ring inside is undamaged, and as long as the pipe is also undamaged, these fittings work really well.
Under our sink, two lines come in. One is for when you’re plugging into the city water, so that’s your mains water in. The other comes from your pressure pump, which comes from your onboard tanks. Both of them join together and go up to the kitchen tap. So we want the water filter placed so it filters both the city water and the water from the tanks.
What I basically want to do is use a 12mm elbow on one line so it joins up with the other through a T piece. From the T piece it goes into the water filter, through the filter, and then up to the tap. That’s the basic theory of what I’m trying to achieve here.
At the same time, I moved the water hoses right up against the side of the cupboard. They used to come down in the way, with a few extra connections, and moving them increases the area in there that we can actually store things in without water pipes in the way.
Cut the Hose Dead Straight, at 90 Degrees
Whenever you’re cutting these hoses, make sure you get a really nice neat cut. It needs to be at 90 degrees to the pipe, not on an angle. If the ends are cut at an angle, they don’t sit that well in the connection point.
You want the hose to fit all the way in. It’s got to go past the little O-ring and sit snug all the way in. If it’s cut on an angle, sometimes you can’t get that pipe all the way in, you don’t get a really good positive seal, and they can leak.
You can get these little devices that cut the hose quite easily. They almost look like a little stapler: pinch them together and they cut it perfectly. I didn’t get one, so I used a good old trusty Stanley knife, took it nice and easy, and made sure I cut it nice and straight. It took me two goes on one of them to get the height right, and that’s fine. Test it, and if it needs to be shorter, cut it again.
👉Want the perfect square cut without the Stanley knife? Grab the John Guest tube cutter and pinch it through in one go!
Leave Clearance for the Filter Canister
I trimmed the first hose so it sits a little bit lower. When the pipe comes across, it needs to go underneath where the filter is going to sit, then up and into the connection.
You need a little bit of clearance under that pipe, because when you pull the canister down you want it to clear the pipe, so you don’t hit the pipe each time. Then it’s just short pieces joining it all up. One of mine was about 15cm, with the right angle connection on the upright piece. Push each one in and check it’s gone all the way down.
Mount the Bracket and Connect It Up
Take the housing away from the filter so you’ve just got the bracket that screws into the wall. It makes it a little bit easier. Find the spot where it’s going to go, mark the points for the screw holes, put a little pilot hole into each of those, and screw the bracket in.
With the filter installed, it’s a couple more pipes: join the pipe into the filter, measure the last piece and cut it off the existing pipe, then feed down the pipe that goes to the tap and connect that last piece on.
Check for Leaks and Run About 20 Litres Through
Now that it’s all connected up, turn the water pump back on and see if you’ve got any leaks. Slowly purge all the air out of the lines.
Once the water filter is installed, the best thing to do is run it for a bit. I think about 20 litres or so. Run that through and let the new filter sort of bed in and get all the impurities out. Then put it to the test and see what it tastes like. Ours looked pretty good.
Our Thoughts
Filtered water going into the tanks, and filtered again at the kitchen tap. For a job that mostly comes down to a few clean cuts and some push-in fittings, it’s a simple one, and we got a tidier cupboard with more storage out of it too.
Do you filter just your drinking tap, or the whole van? Let us know what setup you’re running.
👉For more information on keeping on top of jobs like changing your water filter, have a look at our caravan maintenance schedule.
