Should I be worried?

[avaratz]

Yea builds over time the blue bit I bet there's a blue flow restrictor behind the scale

I would test the hardness of your water to see if you need a softener

We do get scale, as we have very hard water. But it usually appears as a really stubborn, white caked on substance. This is a really slushy, almost gel like substance.

 

[avaratz]

Are they solid crystals or a gel/slush? It looks like Copper Sulphate crystals to me.

I thought it could be that, so was worried about some large scale corrosion going on. But they're definitely not crystal like - they form a sort of slush when you compress them.

 

[ShaunCorbs]

We do get scale, as we have very hard water. But it usually appears as a really stubborn, white caked on substance. This is a really slushy, almost gel like substance.

You haven't already got a softener have you if yes could be the salt out of said softener

 

[avaratz]

You haven't already got a softener have you if yes could be the salt out of said softener

Not that I know of. I searched high and low, but from what I know a softener would be a decent sized box and I haven't been able to find anything in the airing cupboard or under the sink.

 

[Ben-gee]

It could be the ion exchange resin out of a softener, I have known this to happen when a column splits. Makes an awful mess, however the only times I've seen it the resin beads have been yellowish, maybe some makes are blue?

 

[avaratz]

I thought it could be that, but I don't have a softener. We bought the house a couple years back - and have yet to come across one. They're fairly big and need to be accessible so I'm sure we would've by now.

The only other thing I considered was this could be the result of a used up aluminium anode in the Megaflo? It looks an awful lot like aluminium hydroxide would. But from what I've read, the Megaflo has no anode

 

[Welder]

As it's an unvented cylinder, the fine mesh on the control set would stop this from coming from the cold mains. This has to be being introduced on the hot side...

 

[Ben-gee]

Could it be copper sulphate? Could be saturated solution in cylinder which then would then drop out of solution as it cooled, such as travelling along pipes and/or mixing with cold.

 

[avaratz]

As it's an unvented cylinder, the fine mesh on the control set would stop this from coming from the cold mains. This has to be being introduced on the hot side...

That would make sense, given that the shower mixer ONLY has this stuff on the hot supply side.

My boiler was not supplying my tank for about 12 months (the electric immersion heater did the job instead, much to the dismay of my electric bill ).

Someone fixed that in March, by replacing a broken zone valve (IIRC, not 100% sure if that's the right name).

Is it possible this stuff (whatever it is) was sitting in the boiler -> tank supply pipe and has started shifting now, months later?

I'm a complete amateur so my understanding might be way off. I didn't even spot the system was broken until someone fixing an unrelated issue told me it was