Sorry but I never knew this thread was still going! I usually get emails to tell me when there has been a reply and didn't get any so thought the thread had died out. So my apologies for not replying.
Been there, got the tee shirt, etc
So my system at present can't cope with the 2 showers it has, how on earth will it cope with another 3?? Though of course they'll never all be running at the same time.
That depends on what's wrong with it - and what sort of showers they are.
If all it needs is descaling, then the answer may be yes. If it's under specced even when clean, then no.
Simon, I'm so grateful for the time you've taken to try and come up with solutions for me but I'm not quite sure how to use them. I'm a layman and only have a basic grasp of what is going on. Unless I can find a local plumber who has expertise with TS who is prepared to try all this then I'm stuck.
Well you've seen here what "a typical plumber" thinks of something as "complicated" as a thermal store. Real plumbers do exist, but I suspect you'll struggle to find one. BTW - in case there was any confusion, I too am a layman and only do plumbing on a DIY basis.
I really feel as though I should just rip it out and install a Mega Flo.
Can somebody please answer the following question, it's the really important one.
If I didn't mind the cost, would installing a Mega Flo resolve my issues? Would I be able to run 2 or even 3 showers at the same time and have hot water instantly?
Also at present with my system I get mains pressure hot water, would this still be the case with a mega flo including to the loft ensuites (the unvented cylinder would remain in the loft)
Yes, replacing the store with an unvented cylinder is an option. Yes you will still get main pressure hot water. Yes you will still get "instant" hot water (well as long as it takes to get through the pipes if they have gone cold).
Unvented cylinders have their own issues. There is a reason for the strict regulations around them - multiple safety devices, and a recommendation for annual servicing. That's because without all the redundant safety devices, they are exceedingly dangerous. In other countries (the US is one) where the regs are less strict, they do have incidents where water heaters (as they call them in the US) explode. This isn't just "it splits and dumps hot water", this is "it fails and dumps superheated water/steam explosively". Such steam can cook the flesh of people and animals in a matter of seconds.
These videos show what happens if all the safety devices fail (or in the case have been nobbled). The first is one done just in the open, the second was done to see if the heater could punch through a house.
http://www.youtube.com/watch?v=rGWmONHipVo
http://www.youtube.com/watch?v=9bU-I2ZiML0
Over here we have strict regs which mean such incidents are virtually impossible. There are two separate pressure control devices, and two separate temperature control devices. The pressure relief valve will prevent excess pressure buildup, and the requirement for two temperature limits* means that you can't superheat** the water.
* There's a temperature sensitive dump valve, and you aren't allowed uncontrolled heat sources. So the sources should not be able to heat the cylinder above 82˚C, and if they do, then the dump valve will let hot water out.
** In this context, superheated means above 100˚C. You can heat pressurised water above that, but should the tank fail then the water will instantly flash off into steam as it's above the boiling point at atmospheric pressure.
Lest I am accused of imbalance, other systems aren't without their problems. Open vented cylinders can be boiled if heating controls fail, or incorrect system design can result on pumping over into the F&E tank. There have been incidents of the F&E tank giving way, dumping hot water through a (typically) bedroom ceiling - hence regs on construction and support of F&E tanks.
But as Onetap says - ultimately your limit will be what you get out of the supply pipe. If that isn't sufficient then you'll either have to accept lower flow rates/pressures; or have a large storage/header tank, open vented cylinder, and booster pump(s); or an unvented cylinder and booster pumps (if flow is OK, but pressure low); or ...
This is where finding someone who properly understands the trade, rather than someone who just assembles pipes and stuff, will really pay off. They'll know what your local supply situation is (and/or be capable of measuring it), and be able to assess which of the many options would be best for your particular situation.
