On Saturday, 16 March 2019 12:27:16 UTC, John Rumm wrote:
On 16/03/2019 10:11, tabbypurr wrote:
On Saturday, 16 March 2019 09:20:00 UTC, harry wrote:
On Saturday, 16 March 2019 03:44:27 UTC, John Rumm wrote:
On 15/03/2019 12:51, Tim Lamb wrote:

You can get a chemical additive leak sealer. (Similar to
"Radweld") How effective it would be in the HEX, I don't know.

The one used in CH is water glass. It sets hard when exposed to high
temp. IMLE (sample of 1) it sort of worked, but not fully, and that
was with a vented system with a few feet head above the boiler. It
does result in hard but easily broken off crud getting into the
burner area. I presume minimising pressure would help, which might be
helped by putting a bit of air into each rad.

I did try some on this, and it appeared to work for about 5 days. It
might be that the stresses are too high on a HX, or might be I did not
have adequate concentration for the quantity of primary water in the
system.

I expect you have a pressurised primary. The last boiler ran on waterglass with a split HX.


NT