That's because I spent forty years installing, running and maintaining large pipe systems. The only thing they're good for is dry gases and none corrosive liquids.
El cheapo ball valves and water are bad news.
You seem to be missing the whole point of DIYing these things. You get to choose if you want the added convenience and serviceability that having multiple valves adds. It has nothing to do whether its domestic or commercial.
And the most problematic valves? The ones used most often (e.g. taps, cistern valves, showers etc). I have never had a problem with a proper service valve, and they have saved me many hours of time and much inconvenience by allowing sections of a system to be isolated and worked on without disruption to the remainder.
So my personal advice, festoon the system with full bore service valves, makes life much easier later.
Bollix.
Only if they are in working order when you need them. Apart from the main stop valve, the only other useful valves are ones that save having to drain down a tank full of water. So maybe one on the cold feed pipe between header tank and hot water cylinder. Where there is virtually no water to drain, eg cold water system, total waste of time and money. And with the shit isolation valves commonly on sale now, potential trouble. So save money on crap valves and spend it on decent quality other valves.
They are just a consumer rip off, selling people (inferior) stuff they don't need.
A bit like the insurance they try to sell you with just about everything you buy these days. Or unnecessarily complex/shitty stuff that can't be repaired/isn't needed.
Example. Thermostatic mixing valves for showers seems topical.
Well, I've just had a long look and I think the right side could be disassembled after all.
There are only 2 pipes coming off - the mains feed and the garden tap. Both of this should have enough flex (thanks to the offset bend in both) to sling off the top.
After that, the central valve can be undone and the right manifold rotated top towards me. Then it will unclip.
So - yes, bit OTT on the clips, but I think still maintainable...
The only other thing I considered was whether too many clips might strain the pipe, but they are plastic and a) went in according to the pipe layout; b) have a little bit of give. So probably OK...
Will learn to be more subtle next time...
Annoyingly, munsens are 2mm too tall on their lowest settings to directly replace a talon plus one spacer.
I really must measure all my pipe clips (I have a sample of practically every type) and add it to the wiki... It would be useful to know what clips match etc...
I have never had a quality ball valve fail yet...
You do talk cobblers.
For example, when my shower mixer failed, and would not shut off the flow, I could simply isolate it at the service valves I had installed when I fitted the unvented cylinder, order a replacement shower, and fit at my leisure. If I took your advice I would have had to turn the water off at the main stopcock and hence the whole house!
When I notice a tap dripping and want to change a washer, just isolate the tap at its service valve, and get on with it - no need to worry about what other users of water in the house are up to...
Well, a single stopcock for the whole house supply is a bare minimum requirement to let you deal with such jobs but it does mean you could find yourself with a simple plumbing repair turning into a nightmare if you suddenly discover that it might take several days to obtain the necessary spares because the fitting doesn't use the parts you expected to find in use after effectively destroying said fitting during your initial strip down (an all too common event for a lot of DIY repair endevours).
Fitting isolator valves in every concievable feed can be seen as 'overkill' by many despite its undoubted benefits. However, a reasonable compromise imo, would be to keep a small stock of in-line isolator valves handy (perhaps two or three different sizes at most) against the risk of encountering such a situation. If such a 'simple job' turns into a nightmare, you can then fit an isolator valve in the feed to the maverick fitting and then take a more relaxed approach to resolving the problem.
Who knows? You might never need to deploy any of your stock of isolation valves but the 'wasted investment' is a tiny price to pay for 'piece of mind'. Indeed, due to "Sod's Law", you'll almost certainly never have to use up such stock (unless you neglect verifying their 'fitness for purpose', of course!).
+1 to all of that...
Also worth consideration, is that while its entirely reasonable to make the decision that you can fit the valve at the time should the nee arise, it does rather presume that you are going to be there and in a place to actually do the job right then and there.
Last time I on site with a client and got a phone call from SWMBO to say a toilet cistern was filling indefinitely and would not stop, it was far easier to tell her to turn off the leaver ball valve in the cupboard, than where to find my plumbing kit!
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