Central heating header tank - ground floor shut off to tank feed?

Have just installed the central heating header tank, in a little- difficult-to-access loft, with a lever valve right next to the ballcock as it should be.
I'm tempted to add a second lever valve in series with the first, in the ground floor utility cupboard next to the hot water tank.
Should the header tank overflow ever start pouring (or any other part of the system for that matter), it would make for a no-hassle shut- off, until the ballcock/whatever can be replaced/repaired (as well as making for easily controlled system filling).
However, there would always be the temptation for a future owner to shut it off and forget about it.
So trading off convenience against a potential hazard - your thoughts?
The system actually uses a 250L thermal store, so vast amounts of water would have to be lost before the tank/boiler (Rayburn 480K) circuit could get air into it.
I'm also planning to have lever valves on the two tank-to-radiators circuits to isolate them independently from the tank - but obviously *not* on the boiler/tank circuit (apart from the valves either side of the pumps).
Lowest point(s) in the system will be the 3 pumps (2 heating circuits, 1 boiler circuit - so it's "pump plan"), so this seems the obvious place to add drain-off points. ISTR it's smart to raise the dop's slightly wrt to the lowest point to prevent them sluding up. Same with the pumps - have a *slightly* lower point for the sludge to collect?
I *think* there should be no need for air bleed valves, apart from those in the rads - in normal use. But some extras might be useful for system filling, and I can see that the dop's next to the pumps might make for the easiest initial/partial system filling.
Comments/suggestions from those with similar systems or experience?
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Just wondering why you're using a header tank in this day and age?
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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For a straightforward self-install. With a thermal store, there's no real *disadvantage* to a vented system, unless it's a tankless combi system chosen to save space in flats etc.
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Ah. Don't think you mean a central heating header tank?
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Sorry, feed and expansion tank. Header tank is so entrenched in me I can't shake the term.
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Header tank's ok provided you say it's for the hot water. One for the central heating primary can often get away with the cold feed turned off for much of the time.
As regards your extra stopcock, I have one in the kitchen which cuts off the feed after the kitchen cold tap. So I can shut down the feed to everything after that while still having water for drinking, etc.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Do it. There would be no hazard if it got turned of at some time. The worst that would happen is that the F&E tank would dry up in a year or so and the boiler would stop working. This is a fairly common occurence when float valves get stuck in the closed position and the boiler just cycles on its own stat when there is not enough water to circulate round the system.

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