A straight answer

[DaleRCL]

Can any of you guys out there answer this supposedly simple plumbing question for me. Despite having been a plumber for about 7 years I have been told all sorts of answers and never got to the bottom of this one.

Here goes

What is the minimum distance acceptable from the bottom of a cold water storage tank to the top outlet of a hot water water cylinder that it is feeding?

Any answers will be appreciated.

 

[Terrywookfit]

If you consider that an Elson or Fortic type combination tank has virtually no vertical head, then that should answer your question.

The main criterior is the height of any draw offs relative to this point.

 

[DaleRCL]

Good point. All draw offs will be on the floor below as I am considering having cws tank and dhw cylinder all up in a loft.

Thanks

 

[powell30]

Don't expect much pressure tho.......head is so slight the water will have time to wipe its feet as it leaves the taps....

 

[DaleRCL]

I'm going to be fitting a house pump to it so this shouldn't be a problem

 

[TicklyT]

Moving the hot cylinder isn't going to make any difference to the static head at the outlets on the floor below - that's purely down to the position of the cold water storage.

What will change is the flow rate from the cold storage to the hot cylinder with the reduced head available, increasing the chance of drawing air down the open vent.