Nasty yellowy brown stain in my hot water

[Bargeman]

Hello,

I have just had a new gas boiler installed (Vaillant ecoTec plus 428). This has been connected up to the old s-plan system and HW cylinder. However the hot water is now coming out with a nasty yellowish/brownish stain.

I have drained the header tank and cylinder completely and refilled it. Before switching the boiler back on I ran unheated water through the taps and it was clear. However as soon as heating was applied the brownish stain reappeared.

The old boiler was inoperable for about 2 months and we have been heating water using the immersion heater. We had no problem with discolouration of the water whilst heating using the immersion. It is a 1050 x 450 mm cylinder with the coil at the bottom of the tank.

I'm wondering if by heating the tank from the bottom using the boiler coil we have 'disturbed' something nasty that had started growing in the botom of the tank whilst we were using the immersion heater only.

Advice sought and greatly appreciated.

regards,

Justin

 

[Nige F]

sounds like the "boiler coil" is leaking into the Domestic Water (what area of Kent?)

 

[JohnD]

climb into the loft and see which is higher - the small Feed and Expansion tank that tops up the central heating, or the large cold water tank that supplies the taps. the important thing is to look at the water level at the top of the two, and see which is higher above the floor (i.e. if there was a connection between them, which one would run into the other?)

Is your house old enough to have iron water pipes? Are there rust stains in the tank? Or brown sludge at the bottom?

Did you clean the CH system before fitting the new boiler, and add inhibitor afterwards?

Does the stain wash away with water, or does it seem like rust (will clean off with acid drink like Coke)

p.s. if you drain a little water out of a radiator, what colour is it?

 

[Bargeman]

Thanks,

The level in the larger header tank is above that of the F&E tank. We do have iron water pipes at the entry point up to the stop cock, but after draining the tank and cylinder the header tank was clear without sludge in the bottom.

The CH system has been flushed through and has had a cleaner put in it. The intention is to run it for a few days, then drain again and add inhibitor when refilling. During draining the system was pretty mucky.

I guess the confusion is that after draining when we refilled the header tank and cylinder, but before restoring the heating, the water coming from the HW taps was clear. The stain only returned once we turned on the boiler.

A leak from the boiler coil into the cylinder seems a distinct possibility.

regards,

Justin

 

[JohnD]

You say "The level in the larger header tank is above that of the F&E tank"

this would normally cause any leakage to be clean water going into the radiators circuit (and causing the F&E to overflow) rather than dirty water getting into the hot taps. However, a pressure increase caused by the pump may make it go the other way. this could be why it happened when you started running the heating.

Go up to the loft, tie up the ball valves in both tanks, and run the heating, watch to see if the small F&E gets fuller or emptier when the pump is running. Ask people not to run any taps while you are doing this.