Combi - hot water & dirty water

[Bullbags]

Could someone help answer the following 2 questions
1) Why does a drop in pressure on a combi system affect h/w operation. I recently drained system down to change some rads. Turned c/h off, left h/w on timed programme. As the c/h is a separate sealed system I didn't think this would affect h/w operation. Had to leave c/h off for a day and h/w stopped working (boiler lockout?). Anyway, altered rads, refilled system and now all ok. Just puzzled as to why h/w was affected when I thought in theory I hadn't touched this. Is it simply that h/w operation requires 1 bar reading to operate too?
2)Have been getting dirty brown water coming out of bath hot tap from combi. If bath not used for a couple of days then dirty water comes out of hot tap and lasts for about 10-15 secs then goes clear. No other taps affected. Why is this happening?
Hope my queries are clear.
Many thanks.

[dreadnoughtheating]

BB, the boiler does indeed require 'pressure" (pressurised water actually I suppose it should be called) to operate.

By dirty water do you mean 'milky'?, if so run it into a clean glass and see if the bubbles clear to the top of the glass. That would indicate nothing more than some dissolved oxygen bubbles trapped in water - sometimes direct from water treatment works, or again, sometimes from getting very hot in the boiler heat exchanger. So, if milky nuffink at all to be concerned about.

DH

[Bullbags]

Thanks DH. Water not milky, it's dark brown. Similar in colour to what you would get when bailing out the bottom of a header tank.

[dreadnoughtheating]

Hmmmm, waters mixing in a split secondary heat exchanger? - Not good, get an RGI to visit. If you are in an NR postcode area, reply and we'll make contact.

DH

[sooey]

You say you 'left h/w on a timed programme'. Are you sure you've got a combi? Do you have a hot water cylinder?

[kevindgas]

dreadnoughtheating wrote:

if you are in an NR postcode area, reply and we'll make contact. DH

don't think Devon is NR postcode somehow

[dreadnoughtheating]

kevindgas wrote:

dreadnoughtheating wrote: if you are in an NR postcode area, reply and we'll make contact. DH don't think Devon is NR postcode somehow

OK, OK, so give the 'new boy on here' a break can't you? I know things are quiet business wise and yes, Devon is outside my normal work area but you can't blame a bloke for trying

So, if it is a 'Combi', is the filling loop left connected?, although the checkvalve in the loop is not supposed to let system water through, may be its a home brewed job...... just a thought
DH

[gigz]

Bullbags wrote:

If bath not used for a couple of days then dirty water comes out of hot tap and lasts for about 10-15 secs then goes clear. No other taps affected

If no other tap is affected i would say its the pipework to that tap i.e. iron pipe or a rusty/split flexi or even the tap itself.

[jmln]

The brown colour experienced when the tap is not used for a while is iron and is a natural element in water - it is in all ground water in different degrees, however, it is made worse when passed through metal pipes currently being changed to blue plastic as fast as the utilities can afford. Old properties also used iron pipes, again only changing them will remove some of the problem. The water companies will try and reduce it but there will always be some present. I have used a slow sand filter to remove it from a water source down to a tiny amount - it is said to be harmless but it not pleasant to drink it. It is strange how it only shows when it stands due to oxidation which turns it brown as in rust, more so when warmer. If you look inside a storage tank apart from discoloration on the tank sides there is also a furry film that attaches itself to plastic pipes because the two have different static charges which attract this is also evident in plastic pipe inside walls so that when the tap is turned on it flushes away, this is a bacterium of iron normally invisible until static. Copper pipes have a sanitising effect which prevents this occurance so beware when choosing plastic water pipes although the water companies are using it as a replacement to metal. If you choose copper for the last supply chain you should not get any of this through the tap.

[Boilerman2]

That's Deveon Soft water for you