Safely Removing Stuck Tap Insert from Kitchen Mixer

Hi Guys

I'm thinking about trying to remove the cold tap insert shown in the picture here, but it's fairly stuck (maybe limescale):


I've turned off the water supply using the tap isolation valve fitted beneath the sink. So far, the tap insert won't budge with the limited amount of force I've applied with an adjustable spanner. What I'm worried about is using too much force and damaging the tap pipework, as I don't have the skills to fix broken pipework.

Here's how the mixer tap looks from below:


There are three pipes coming down, and the back one is hexagonal, which I assume is somehow keeping the mixer tap in place. How much turning force on the tap insert do you think this installation could take?

To unscrew the tap insert by applying force, how would you prevent damage to the tap pipework? I'm thinking that putting blocks of wood behind the tap base would prevent rotation, or perhaps buying a special tool to clamp the mixer base would be worthwhile?

Thanks for any thoughts.

Easy.
Pour very hot water on to soften any goo.
Take off both tap heads. Put a spanner on one in the undo direction, the other in the do up direction.
Apply force.
If that doesn't work, then with your third hand, hit the end of the undoing spanner with a smallish hammer.

That insert will indeed unscrew, but its a good idea to hold the tap firmly somehow as you apply more pressure.
The brass hexagon you see does hold the tap down to the sink.
Its unlikely to cause any water issues if you do move the tap, but you don't want the rubber washer between the tap and the sink to dislodge as splash water will tend to drip through after a while.
John

ChrisR said:

Easy.
Pour very hot water on to soften any goo.
Take off both tap heads. Put a spanner on one in the undo direction, the other in the do up direction.
Apply force.
If that doesn't work, then with your third hand, hit the end of the undoing spanner with a smallish hammer.

Click to expand...

Never come across the two spanner trick Chris - cheers!
John

ChrisR said:

Easy.
Pour very hot water on to soften any goo.
Take off both tap heads. Put a spanner on one in the undo direction, the other in the do up direction.
Apply force.
If that doesn't work, then with your third hand, hit the end of the undoing spanner with a smallish hammer.

Click to expand...

So, you are saying put a spanner on the cold tap insert, and a spanner on the hot tap insert, then undo the cold tap insert (anticlockwise as you look down on it, correct?), whilst "doing up" the hot tap insert (clockwise as you look down on it, correct?).

You don't think there's a risk of overtightening the hot and getting it stuck?

Should I apply hot water just before attempting the undo? Could that not cause expansion and make the insert harder to undo??

Many thanks