I am in the process of replacing my cold water tank in the loft on a fully pumped CH/hot water system. The flow from the hot taps has always been rather poor. I am in a top floor flat hence the available attic space.
The hw pipe from the tank leaves as 22mm and then immediately reduces to 15mm before it leaves the airing cupboard.
1) Would replacing the existing 25 gallon tank with a larger 50 gallon tank improve things?
2) Would raising the tank from the loft floor and putting it on a stand help? I would probably only gain about 1m in height if I did this.
The two things which influence flow rate are pressure and pipe resistance. On a gravity system such as yours, the pressure is determined by the
*vertical* distance between the top surface of the water in the header tank and the hot tap in question. Having a larger tank will not affect this at all (unless this also results in a higher level). Raising the tank will make
*some* difference, but maybe not all that much. If you can easily raise it while replacing it, do so - it can't do any harm! Also a bigger one would be good to make sure that you can use all the hot water in your cylinder before emtpying the header and thus not being able to expel any more hot. Bear in mind, though, that water is heavy stuff. A 50 gallon tank full of water weighs 500 lbs plus the weight of the tank itself - so you need to make sure that you build a strong support for it.
Pipe resistance is determined by pipe diameter and the number of bends and elbows around which the water has to flow. The flow path to a hot tap includes the feed pipe from the bottom of the header tank to the bottom of the hot cylinder and the pipework from the top of the hot cylinder to the taps. It is well worth while ensuring that as much as possible of this is
22mm - if not 28mm - and that sweep bends are used rather than elbows.
Mike - where can I get one of these? I've used the booster pumps for 15 mm copper (mixer shower), but can't seem to find one for 22mm which I would need for hot water. My problem is similar to the OP's
Thanks Set Square for a concise answer. Pretty much as I thought. There is no point in buying a larger tank. I will look at raising the tank but if it proves too difficult I probably won't bother.
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