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Air vent for water tank.

This is a cold water tank and it has an air vent at the top. A right angled elbow comes out of the tank and a 8mm copper compression fitting joins it to a plastic tube (Like wine syphon tube).

This wanders about through bulkheads etc before joining back onto a copper tube which goes through the side of the boat.

It is blocked and I've identified that the blockage is in the final copper section.

The owner says that the tube needs to have a filter, as he doesn't want earwigs dropping into his kettle when he fills it up ! Shocked

So I have to cut the copper pipe and replace it , but what to use for this filter ?

At the moment I have in mind a small piece of stainless pan scrubber pushed into the tube, or some nylon gauze (old tights )

So the filter has to allow air to go both ways and to allow water to pass outwards so it comes out from the end of th etube and he knows to remove the hosepipe and stop filling the tank !

Just a little bit of something rolled up and pushed into an 8mm copper tube - Any ideas ? Confused
Graham Hyde

Falstaff, you mention boat, is this a sailing boat or a barge?

If you've got something just balled up and put in line, isn't there a risk that it will be pushed in when he fills up with water. It's also likely to be hard to get to when it finally blocks, with either an earwig, or limescale.

At the arse end of our washing machine water inlet is a stainless steel mesh 'cap' that sits inline and can be accessed easily, but it held in place on a rubber washer.

That should do the job, no?


it's a "Cabin cruiser" Graham, so reliant on engine power. A bit like a floating caravan really.

I'm not explaining properly Nick. There is a separate filler tube about 37 mm dia which you stick a hosepipe into. This goes to the tank low down, so the water level as it rises cuts off the escaping air from this tube. The air vent is at the very top of the tank. This is about 8mm dia and is the one which is blocked.

This is also the one which needs the filter to stop detritus and insects getting in.
When the tank is full, the water goes up the air pipe and also spills out of the main filler pipe.

That idea of yours gives a starting point Nick and I had a look on ebay too and found this :

I reckon that'll do the trick and it's just a shame to cover it up after !
Rolling Eyes

I'll make a point of showing him though ! Wink Cool
Graham Hyde

Hi Falstaff.
So, a tell tale as well as a breather.
Various options but stuffing something up the tube not one of them.
I would be tempted with a simple solution as gauze taped over the outlet. A piece of nylon tights with an elastic band would do as good a job.
As you need to be able to remove the filter on a regular basis to remove the build up of algy and debris an easy method of removing, cleaning and replacement is preferred.
The tubing inside the boat tends to get a coating of greenish mold, I swapped mine with food grade tubing and rinsed regularly with a chlorine based solution.
If you do go metallic, watch out for dis-similar metals.
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