Limescale removal from CH sytem

[letmedoit]

8 months ago I got good help from this forum to cure a CH system with cold ground floor rads. During that time the system was well flushed through with Sentinel X400 System Restorer and re-filled with X100 Inhibitor. I also took the opportunity to back-flush all the rads and fit a Spirotech Magnabooster 2.

Since then, the DHW heat-exchanger has blocked up with lumps and bits of limescale. Removal and back flushing (I am used to doing this now) cured the problem but only until next time.

The system is 40 years old and originally supplied from a very hard-water supply (300ppm !). 15 years ago we fitted a water softener and all re-fills have been with softened water and inhibitor. 8 years ago we had an Alpha CD24C fitted and since its second year, I have been removing and back flushing the DHW heat-exchanger every 6 months !

Is there a flushing agent which is best for dissolving/removing the limescale that is in the old system and would rid us of this regular need to dismantle and flush the DHW heat exchanger ?

Thanks

 

[letmedoit]

No suggestions ?

I really would like to sort this out before we put our CH back on when the cold weather starts.

 

[Youllneverguess]

Christ is was only 45 minutes

 

[dcawkwell]

Fit a good unvented hot water tank with a magnetic limescale reducer
in line. Problem solved it isn't going to blockup.

 

[ServiceNumpty]

By your description it sounds like it is blocking on the central heating side, if it;s on the cold water side fit a filter their.

 

[letmedoit]

By your description it sounds like it is blocking on the central heating side, if it;s on the cold water side fit a filter their.

Yes, it is the central heating water side within the DHW heat exchanger. The cold water side is fine as there is already an in-line filter ahead of the flow-valve diaphram, which has always been clean when I have checked it.

The CH was only used for a few weeks since getting the cold GF rads. sorted-out before being turned off (IIRC Easter was rather hot !). The boiler has been set for DHW only ever since.

 

[ServiceNumpty]

Where has the Magnabooster been fitted, if it is on the return, you shouldn't get any crud in the boiler, I'm guessing this is crud that has been circulating within the boiler itself.

 

[letmedoit]

The Magnabooster has been fitted below the boiler in the return pipe from the rads . It should have caught any crud that might have been floating around the system before it was switched off at Easter. I did drain it off into a washing-up bowl after 4 weeks from fitting but, though the water was getting black (again) there were no significant bits in the bowl.

The back flushing had been done using the filling loop and included closing the CH-return isolating valve so it would flush through the main heat exchanger, down the CH flow pipe and out the drain valve.

I understand that the crud which blocked the DHW heat exchanger this time must have been circulating around the boiler (becuase the CH was no longer in use). I am just completely fed-up that despite all of the ^^^^ work the DHW heat-exchanger had blocked up yet again (ok this time after 8 months not 6).

 

[letmedoit]

Christ is was only 45 minutes

Thanks for your really usefull and helpfull comment (not) !

But if you check the times you will see - youllneverguess - it was actualy 3 days and 45 minutes !

If you have anything else to say - it has already been ignored.

 

[ServiceNumpty]

If the water is going black, it hasn't been flushed properly - simples.

Start from the beginning, take every rad off one by one and using a garden hose flush every rad. Then flush the pipework and boiler.

 

[letmedoit]

If the water is going black, it hasn't been flushed properly - simples.

OK, I accept what you are saying. However, the magnatite still in the system is not currently a problem and I hope the Magnabooster will eventualy deal with that anyway (and catch the bits of old limescale in the process).

I take it there is no easy way of dissolving the limescale out (like descaling a kettle) ?

Meantime, as it is easier than removing all the rads, will I have to expect to remove and backflush the DHW heat exchanger a few more times ?