Pipework sizing and connections

[Bogart]

Posted a message before about new position for kitchen sink and feed to it. Was told best is mains and not tank, to which I definitely agree. Was going to run a new 15mm cold feed from mains to this tap but as that will involve drilling through quite a few kitchen ceiling joist I wondered if there was an alternative.
There is a H&C feed near to the new position but the cold feed is from the tank.
I have attached a drawing which shows the setup. Now as an experiment I am considering installing a pipe, dashed line, between the 22mm mains feed and the 28mm pipe from the tank, installing a valve at point A to effectively enable the tank to be isolated.
With the place being rather old, 16c there is a real mixture of mains fed and tank fed cold supplies.
As an aside the main bath tap is a bath/shower mixer tap. Supplies to both hot and cold arrive in 22mm so obviously at some point the hot 28mm reduces to 22mm on its way to the bath. The cold feed is from the mains. This results in getting the temperature adjustment of the mixer very difficult, the smallest of adjustments to the cold tap results in a large temperature variation. On this evidence I am assuming the mains fed is at a higher pressure than the tank can provide.

Hence I am hoping if I can effectively run everything off the mains this should alleviate this problem to some degree.
All comments gratefully received.
Regards

 

[centralheatking]

This is how I would do it. Bath hot and cold tank fed, you could even do the bog tank fed. Anywhere else ought to be cold mains fed....bathroom basin aswell as teeth cleaning, kitchen cold outside tap
and washing machine point. It is best to get it all sorted out properly. Make sure the tank has an effective lid as debris and dead pigeons can taint the water somewhat. Centralheatking

 

[steadyon]

If you do what you are proposing, then the hot water cylinder will be at mains pressure. They are not designed for these pressures and would likely burst.

 

[Bogart]

This is how I would do it. Bath hot and cold tank fed, you could even do the bog tank fed. Anywhere else ought to be cold mains fed....bathroom basin aswell as teeth cleaning, kitchen cold outside tap
and washing machine point. It is best to get it all sorted out properly. Make sure the tank has an effective lid as debris and dead pigeons can taint the water somewhat. Centralheatking

Hopefully lid is sealed well enough to stop pigeons, not sure about the mice of chaffinches that live up in the loft
Changing the bath cold to tank fed easier said than done as the 22mm pipe disappears into a partition wall and have no idea how the mains gets into the bathroom, plus the washbasin cold in the bathroom is tank fed which as you say should ideally be mains fed, so a bit arse about face!

 

[Bogart]

Tank states max pressure 10m or 1.45bar, which in themselves do not equate with 1.45 bar being about 14.5m.
The base of the cylinder is approximately 3m below the max height of the water in the feed tank.
If I connect up as shown in the drawing only problem, quite a big one in my mind, is the water pressure would force water up the 28mm pipe into the feed tank, not an ideal situation!
So my proviso is to take the new feed, the dotted line, not to the 28mm pipe but to the 22mm feed and do away with the 28mm/22mm T piece. In this situation the tank does the hot water cylinder and nothing else.

 

[ShaunCorbs]

The extra .45 would be the head pressure of the water in the tank

 

[Bogart]

The extra .45 would be the head pressure of the water in the tank

Is 4.5m not 0.45m not sure how they equate the two figures.

 

[ShaunCorbs]

Is 4.5m not 0.45m not sure how they equate the two figures.

bar 0.45 bar due to the weight of the water water

 

[Bogart]

Surely the maximum pressure equates to the head. So what I am saying is if the tank can stand 1.45bar which equates to a 14.5m head where does the 10m figure come from. To exceed the tanks pressure the top of the water in the feed tank would have to be 14.5m higher than the cold inlet on the cylinder.