**boiler Question!**

[Lisa_Louise]

Any plumbers or boiler people who can help with this query please?!
What is the difference between a combi, system and open vent boilers ?

I am used to a combi boiler, instant hot water on demand, whenever I need it. I am moving to another property but it has an open vent boiler.... I have an idea what this is but cannot find more info... Like, does this mean I now have to wait for the hot water cylinder in the airing cupboard to heat the water up to have a shower, wash my hair or have a bath? Or is it like a combi where the hot water is instant and no waiting around for the water to heat up? Is there Anything else I should know that is different to a combi?

By the way, the boiler in the next place is a Vaillant ecoTEC plus 415 if that is any help!

Much appreciated

[donny48]

http://www.aphc.co.uk/UNDERSTANDING%20HOT%20WATER%20SYSTEMS%20IN%20THE%20HOME%20Dec13.pdf

[Lisa_Louise]

Thank you donny! Does anyone know where the cold water is sourced from? Is it from the cold water tank in the roof, the cylinder in the airing cupboard or from the mains? I'm confused by this system as like I said, I'm used to a combi. I'm a bit annoyed as the person I'm letting from said it was a combi (she didn't have a clue what system it was) and no we've signed a contract for a year with a boiler I know nothing about! I've read that harmful bacteria can grow in storage tanks.... That has worried me now.

[bhg481]

The cold taps in the kitchen are normally fed directly from the mains. The cold taps in the bathroom can be either; ours were fed from the storage tank but I converted the sink tap to be direct from the mains That's a very simple conversion if you are worried about cleaning your teeth with stored water.

[KARL]

Combi boilers heat water directly at mains pressure and basically produces ".... instant hot water on demand..." and it only heats what you actually use. Vented systems involve mains water being discharged into a vessel (header tank) which then goes by gravity to another vessel (cylinder) with a heat exchanger. Is it "...I now have to wait for the hot water cylinder in the airing cupboard to heat the water up to have a shower, wash my hair or have a bath?..." - yes it generally is and shower pressure balance between mains cold and gravity hot can be tricky. In the latter the volume of the cylinder is partly or wholly heated and stored until it is used (some heat loss over time).

If Brexit means rolling back European influences/regulations/laws and going back to genuinely (old) British ways then combi boilers will again be "dangerous" and forbidden for not meeting the regulations. If I am not mistaken, they were first developed in Germany and were widely in use on the mainland quite a bit before British regulations eventually began to tolerate them. Foreign (modern, non-syphon) toilet flushing mechanisms became accepted at about the same time.

[bhg481]

Karl - showers should not be fed from mains cold water. If you are showering and someone in the house turns on a kitchen cold tap, the pressure will drop and the shower could scold the user.

[Lisa_Louise]

Thank you bhg and KARL...

Karl, how easy was it to convert your sink tap to the mains.. What did you need to do? Is it costly? I am worried about brushing teeth from a storage tank to be honest! How can I tell if the bathroom sink's cold tap is drawing water from the tank or mains? I will test this next weekend when we gets the keys to the property.

[Lisa_Louise]

Sorry, that last question was for bhg!

[SnookerPlayer]

Turn the water off at the main stop cock and see which taps still work.

[SnookerPlayer]

I would think that the toilet is fed from the mains, not a big job to tap off to feed cold basin tap, if the cold is fed from storage tank.

I would expect change out of £50

[Lisa_Louise]

Thanks snookerplayer! I guess that was pretty obvious lol

[bhg481]

The header tank in the loft is supplied directly from the mains; the cold feed to the bathroom sink comes out of the header tank. Turn off the mains, cut cold feed to header tank and insert a "T" piece into it. Drain header tank. Cut cold from header to sink and cap it off where it leaves the tank. Connect the other cut end (to sink) to the new T piece. Turn on mains; job done for the cost of 1 T piece and one cap (+ labour). When you turn the mains back on the water will refill the header tank and will also be connected directly to the bathroom sink cold tap.

[bhg481]

Bear in mind the the bathroom sink cold MAY already be fed from the mains. I would expect the toilet to have the same feed as the sink tap. As others have said, turn off the mains and see which taps don't work anymore. (You might still get a bit of water out of some taps until the pipes empty but it will be at reduved flow).

[Lisa_Louise]

That's above me, bhg! But thanks anyway!! I don't suppose you live anywhere near Romford, Essex do you and fancy a bit of cash? Haha!! ;)

[bhg481]

Reading is my stamping ground Lisa - the point is that it's a simple job so shouldn't be too costly.

[KARL]

We had mains fed cold with gravity hot to the shower for many years without any problems (e.g.scalding) but, as I said, balancing the supply to it was necessary. This was satisfactorily achieved but the matter could be overlooked in a form of ignorance.

[bhg481]

I wonder who installed that Karl. I was never a plumber by trade but I did look up the regulations many years ago when I installed my own shower and I think it's actually illegal to plumb it that way.

[The Builder]

All good, but I can see one flaw with bhg's "conversion" in the roofspace with the cold water cistern.

If you cap off the 22mm outlet from the tank in the roof, and connect the pipe run to the mains, then, yes, the sink etc will become mains fed........

................. but, so would the cold feed to the immersion cylinder, and you definitely don't want that. The immersion cylinder would then keep filling indefinitely because there would be nothing to ever stop it.

Occasionally, you find 2 outlets on the roof tank. One for sinks & WCs, and the other for the cylinder. This would be easy, but I doubt if you have that arrangement.

[bhg481]

My bathroom sink was fed by a 15mm pipe and the bath by a 22mm pipe - I assumed all houses were the same since sink taps have 15mm connections and bath taps have 22mm connections. My current house was built in 1982 - perhaps things have changed since then.

[Lisa_Louise]

That's interesting the builder.. It's too complicated for me to so will get someone in anyway, I just hope the cold taps are connected to the mains instead of the tank, to save all this hassle!

[The Builder]

Lisa, I think you're wise to leave it alone until someone can look at it and find out exactly how it's all connected up... and go from there. Bathroom WCs and basins (sinks) have been mains fed for many years. BHG's 1982 house would most likely have been gravity fed as he says. If your house is newer than that, then I'm willing to bet that your basin is indeed mains fed as you would wish.

If I may reply to bhg's latest post...... 15mm or 22mm is actually irrelevant here. Baths today are 15mm fed (mains), then converted to 22mm to connect to the bath tap.

My point, in my previous post, is that the most common set-up was to have all the cold outlets in the bathroom rooftank-fed (gravity). Branching off from this was the cold feed to the bottom of the immersion cylinder.

That's where the problem arises. Even if the WC/bath/basin colds were converted to mains fed, then the immersion cold feed MUST remain as gravity fed.