2 x loft tanks

Hi
No problem if they're 6 ft apart, just make sure the ball vale is in one tank and the outlets in the other, , and of course, over flow, about 2 inches below ball valve.

Also, remove any lagging under the tanks.

Regards
Peter

 

Hi
Speedfit will no ok, need at least 22 mm, 28 is better, to join tanks that is.

Vent pipe discharging to tank, ? Well technically it's not good, but in the real world, any tank is ok.

( it's said, that if the system has a fault and hot water vents over into the cold tank, it will/ could, raise the temperature above 20c. This is then a breading ground for legionella)


Bit over the top, but that's how it is in public building etc...

Regards
Peter

 

Just noticed, spell check error. Will be ok for speedfit...

 

Legionella, the risk of contamination is small, but it has happened.

 

All water naturally contains the legionella bug and it's perfectly harmless to drink.
It's only when it is allowed to breed into very large quantities and then it still needs to be injected into a fine mist then breathed in by a human and only then does there become a slight risk of that person contracting legionella.

A lot of time and money is currently being spent spouting sear rubbish about legionella.

Having said that you don't want a heating expansion pipe discharging all that ***** out of the heating into a domestic tank!!
Tappy,

 

So old fashion having header tanks in lofts in 21st century...

 

As above no problems with two connected and use 2x22 or even maybe 2x28 - the link needs to be the same or preferably greater than the total take off. Try to put the take off at the opposite end from the connecting pipe too - you are trying to encourage flow and alleviate any dead spots.


When you say "heating vent pipe" - is that from the actual heating system or is it the expansion pipe from a hot cylinder?

 

You need to connect the two tanks together and there must be a good flow through those that can equal, or be greater than the drain on the tanks from hot and cold water usage.

To treat it simplistically, you will have two outlets, a cold feed to the taps and a hot to the cylinder - assume these are 22mm pipes. The internal bore is nominally 18mm and thus the cross sectional area is 255mm^2. With two outlets the total is therefore 510mm^2.

The pipes connecting the two tanks should have a cross sectional area of at least the same amount or you will drain the second tank faster than it can be refilled by the first. Taking gravity and pumps into account can make it even worse.

If you connect using a single 28mm with cross sectional area will be around 450mm^2 which is 10% less. It might just about suffice but you could end up draining the second tank if all taps were being run for an extended period. 2 x 22mm in parallel will have the same 510mm^2 and would allow a faster transfer of water from the first to the second tank. Putting two 28mm pipes in parallel will give a good potential flow rate significantly greater than drain that will occur.

If it was me for the extra cost of a few pounds I would be going for two 28mm pipes in parallel.



The hot cylinder expansion is often fed back to the cold tank ... not sure which one of te two it should go too though.

 

Always pays to over engineer abit, having two 28mm pipes in parallel is better.

 

Not so much "over engineer" but design for all eventualities.

 

Same as over engineering in my book.

Like other month, friend was having new water main pipe fitted, I got water board chaps to change to a 32mm pipe instead of 25mm which they were going to use, if then he decided to build house in meadow, mains could cope with extra demand.

 

I am actually a design engineer by profession and to me they are different. Designing for all eventualities means looking at current and future needs and creating something that will meet future demand in 99% of cases. Over engineer means to look at the future needs, work out what is needed in 110% of case and still make it larger with the inherent waste of money

I know they got it wrong. When the M25 near Heathrow was built they estimated that it would need 2 lanes and possibly 3 in te future - we now know that 5 or 6 would deal with te traffic over 95% of the time. So, if at day 1 they had "designed for all eventualities" they would have specified 6 lanes with land available and services located well to the side for a possible 8 lanes. Over engineering would have said - fully build 10 lanes

 

What do you mean by rigid? Using PEX pipe - Hep2O, Speedfit or others is fine.

 

I have known peeps to use 32mm mdpe pipe to connect tanks in a loft.