White mould blobs on water surface of header tank

[asitwas]

18/5/09 Hello All.

Central heating modifications a few weeks ago. Now there are lots of white mould blobs floating on the water surface of the new plastic header tank. Not seen any previously.

Cleaner chemical added, while system was hot with circulator pump running for a few hours, then water was run through with drain cock open. Extra two drain cocks fitted in the process.

Then a new condensing boiler was fitted and 6 out of the 8 radiators were renewed. All done by Corgi man.

Cleaner chemical additive stated on the installation sheet as Sentinel x400. The inhibitor added when water refilled is stated as Sentinel X?00. The writing looks as though it might be X100 or X700

Anyone know what I should do? I drew the plumber's attention to it today [when he came to replace the new but faulty pump] but he did not offer to get rid of the mould.

 

[JohnD]

1) how do you know it is mould?

2) buy a bottle of Fernox AF10 from a plumbers merchant. They may have to order it. Read the instructions. It is about £25 but twice as much as a typical house needs so keep the rest next to the tank for the future. Make sure all plumbing work is completed before you use it to avoid wastage from draining.

Sentinel X100 is a popular and good-quality corrosion inhibitor. I don't think Sentinel make a biocide.

 

[bengasman]

It sounds like he did not clean the system properly.
Not a vision shared by all on here, but personally, I find installing an open vent boiler in the 21st century rather questionable.
In stead of dropping a hint, you could call the installer again, and tell him you want it sorted.
The money he received wasn't molded, so why should your new boiler be?

 

[asitwas]

Thanks JohnD for the reply. The blobs are puffy looking and are very white in colour and resemble mould growth but yes, I can't be certain it is not the solidifying of the chemicals from the x100. I have no experience with the stuff.

Previously, with my own repairs keeping a potterton boiler going for the last 45 years, I used Fernox F1 and had no sign of any problem with mould. As this was a new type condensing boiler, of which I knew little, I got an 'expert' to do the job. I see Fernox claim the F1 is anti-bacterial.

Heat will probably have killed off any bacteria that is inside the pipework/radiators etc, and there is no air for its growth, so I guess I just need to tip some of what you suggest into the header tank -- after clearing most of the mould out. And then check it occasionally. No leaks should mean little or no dilution.

I don't want to drain the system down as there is a plumber's 12 month guarantee.

I have sent Sentinel an email about it to see what they say.

 

[JohnD]

just before adding the AF10, I would bale the tank out and sponge it clean to remove all discernable traces of fungus.

make sure it has a tight-fitting dark lid, and an insulating jacket to keep the heat out (seriously) on hot sunny days.

let us know what Sentinel say as I think they are missing a trick.

 

[asitwas]

Thanks JohnD. Will do.

 

[heytesto]

Fernox is supposed to inhibit bacterial growth.

In the old days of Fernox MB1, 3/4 went into the system and the final bit into the header tank once filled.

 

[asitwas]

I now have an email. I quote the main bits:

"The mould is the result of airborne bacteria and not the result of the inhibitor added . . . the bacteria will not have any negative effect on the operation of the system unless you fully drain the system again. . . remove this bacteria . . . by ‘skimming’ . . . then doing a low level of domestic bleach into the header tank."

Not the result of the inhibitor, eh? So the mould would grow on top of clear water, without inhibitor? Me thinks not.

Of course it is the result of adding their inhibitor. And any intake of water will now insert the mould blobs into the system.

I see that Fernox sell both MB-1 and F1. I wonder which of these is best for refilling the system with?

 

[JohnD]

...then doing a low level of domestic bleach into the header tank."

Sentinel say it's OK to use bleach? that's great, it will save me money next time. Do they say how much?

Anyone know any objections to this?

 

[asitwas]

Update.

I have just looked in the tank and the white blobs have gone and left just two dark brown flattish flotations. Presumably the result of died mould. Murky water stops me seeing the tank bottom. I will leave things as they are for now.

 

[glasgowgas]

to mr asitwas,

please keep us updated with how you get on with any feedback from Sentinel.

its good to have this info in the back pocket so to speak

best of luck..

 

[asitwas]

Not sure whether the mould died of its own accord or if the plumber put his hand in and pushed the mould under. It has vanished quickly. I saw it Sunday and he looked yesterday (Monday) when he came to change a faulty pump. So I need to check it again at a later date.