HW cylinder issues

[Goldengator]

Hi there, we have had an audit on the HW cylinder in the building we have recently moved into,

Can somebody please let me know what the issues are with the installation relating to the report. I know that the pipework is shocking and the discharge pipework is also incorrect,

 

[Justin Passing]

If you mean you don't understand what it says, it's complaining that there isn't a hot water return, though stubs etc are there.
The point of a HWR is twofold:

1) to reduce the waiting time at the taps, especially those further from the cylinder. If there's a circulation pump running (can be timed, by the way) then the loop is always hot so the unheated branch pipes will be short.

2) To get all the cylinder up to the same temperature. with no HWR you get "stratification" in the store. Hot water rises, so the cylinder sits there with hotter water at the top. It's less of an issue with horiz stores but look where the heaters are and where the thermostat/s is/are. And where the outlet is. If the water's being circulated, it'll be more or less even so you won't get half a store of lower temperature water.

It could be a right and proper PITA to run the what-the-book-might-say 22mm all the way from the top floor to the basement. You CAN get away with a 15mm plastic pipe, which with a bit of luck is easier to thread through. I have done that and it worked well enough.

Be mindful that you will have a lot of hot pipe losing heat all the time, both flow and return, so it should be well insulated.
You can argue about when the circulation pump should be tined to be on. Morning and evening to match draw off times, is popular.

NB it need to be a pump designed for the purpose, not a Heating circulation pump. ££+.

 

[Exedon]

Just to be clear you can't use standard plastic pipe on secondary circulation systems .
Needs to be copper or pipe rated for job we use tectite metal with tectite classic fittings with correct inserts.
Pump needs to be bronze or stainless steel.

 

[Goldengator]

Hi there, many thanks for the reply’s. So going forward what do I need to do to rectify the issue? The system currently works fine it’s just this audit has picked this up and said that an alteration to the pipework or pump needs to be made? thanks GG

 

[Goldengator]

This audit was done originally by an engineer checking legionella testing and noted that the pipework might be causing contamination?

 

[Justin Passing]

you can't use standard plastic pipe on secondary circulation systems

He's right - I forgot that! Tektite was what I used, it was quite a while ago.. It's expensive but it's nice to use - stays where it's put.
Flexible copper would do but it goes hard quite quickly and isn't so flexible then.
You also need a non-return valve, and to keep the flow in the loop right down, too. 0.5m/sec comes to mind.
You can add a pipe stat as well, to reduce the time the pump was on.

Contamination? Not with dirty water, but you can get Legio with standing warmish water, so you need a cycle at above 60°. Conflicting needs, it can get complicated.

There's a British STandard book which spells it out, and a quick search found this, which is freeeeee:

https://onlinelibrary.wiley.com/doi/book/10.1002/9780470690277