Pipe scale-A myth?

[sPoNiX]

Currently taking the CH apart and updating various things. The system and pipework are over 30 years old and we live in a very hard water area.

Had to remove a section of incoming main (15mm) and to my astonishment it was virtually limescale free. There was a very fine layer of powdery limescale but you could wipe this off with a finger.

Also, removing a section of pipework from the radiator circuit showed that to have only a very fine layer of magnetite. The water removed from the rads had a slight dark "tinge" to it but nothing severe.

The pipework genuinely hasn't been touched in 30+ years. The previous owner stated that he did nothing to the CH system apart from hoover the boiler out every year.

I'm starting to think all this stuff about limescale blocking pipes is a load of rubbish.

Kettles and appliances yes (I have seen that) but pipework no..I assume heat makes the difference?

Has anyone any first hand experience of pipework becoming seriously scaled up or is it a myth?

Can anyone explain why my 30 year old pipework is scale free?

sponix

[EricP]

Depends where you live. Some parts of Wales have lovely soft water, London has cement in the pipes.

[Andy Hall]

You wouldn't expect to find scale in the cold water pipes. If you think about it, if that were to happen, all the street mains would be in severe trouble by now. The calcium and magnesium compounds in scale come out of solution on heating and generally on the heating surfaces, so you would expect to find it on the surfaces of the coil inside the HW cylinder and possibly inside some of the pipes in the near vicinity. On older systems with a direct cylinder where there is no coil and the DHW circulates by convection through the boiler, you would expect to find scaling of the boiler and pipework from it.

The water in the heating circuit seldom changes, so no significant scaling there. If the system doesn't have problems with pumping over or sucking down because of pump placement and pipework, then initial dissolved oxygen, causing corrosion would be used up.

You might find that if you check the radiators, there is more magnetite in these since the water is crossing radiators at a lower speed at a given point than it will be through the pipes feeding them. Hence material is deposited, typically in a triangular shape at the bottom.

[Andrew Mawson]

system

astonishment

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previous

Incoming main is cold - the lime tends to come out when warm.

C/H pipes - so long as system isn't constantly emptying and filling you only have the lime held in 'one fill' of the system to deposit on the pipes so not much should be there.

On the other hand the domestic hot water pipes and inside of the hot cylinder I would expect to be encrusted in limescale.

AWEM

[david lang]

You can check your water hardness by entering your post code into a box on

I have checked this with areas I know to be hard & softa water and it hasn't failed yet.

It does indeed, at about 70 centigrade the calcium (mainly) salts come out of solution and stick to metal items like pipes.

Sure can. Industrial high pressure hot water cleaner 160 bar @20 litres/min I once installed in Gosport, Hants scaled up sufficiently to almost block a

10mm pipe completely - did it in less than a fortnight and kept doing it. We added a chemical scale inhibitor, reduced the heat to below 70 c and made the operator run it cold before stopping use. This didn't stop the problem, just reduced it a lot.

The cold would be, the calcium salts stayed in solution. With the hot, once the scale had come out of the original fill water, that's it.

Dave

[sPoNiX]

I'll check the cylinder when it comes out and see if it's more scaley.

sponix

[nrh]

In news:5ivwf.23244$ [e-mail], david lang scribed:

Thanks for this.

Nigel

[Rob Summers]

Hmm. I beg to differ. Out of three postcodes of which I tried and which I know the hardness of the water it managed a not too amazing 1 out of 3.

Rob

[Brian G]

Rob,

If you mean it didn't recognise two of the post codes - I had the same problem.

It would appear that their post code database is (shall we say) a little out of date. Ours changed about 10 years ago from NP1 to NP11 and I had to input the old one to get a result - a soft water area, which I already knew.

Brian G

[Jeff]

If you check your local water co website it will tell you the hardness of your water without bias ( they have no product to sell )

Regards Jeff

Regards Jeff

[Ed Sirett]

Your system was in good order.

Where new water is being frequently added to the circuit scale can be a problem and corrosion due to the dissolved oxygen.

Posts and replies here are often dealing with troubles causes by problems which you simply have not had.

[Ed Sirett]

An inch or two of flakey stuff is quite common after 20 years.