Can you help explain the components of my water system?

Question

I've moved into an old stone house in the UK. The water system consists of:

1. Some type of well under the conservatory. It looks very deep and has a good flow rate according to the survey.
2. A submersible pump inside the well that pumps water up the hill behind the house to:
3. A very large water storage tank. Then the water goes back down the hill into the house, where it also goes up to:
4. A small water storage tank in the loft space below the roof. This feeds into a:
5. Hot water boiler on the first (2nd in US) floor right below the loft tank.

I keep getting various advice on what all the various components are doing and which are necessary. My questions are:

1. Why is the storage tank on the hill necessary? The well has enough water throughout the year. If it's to increase pressure, then:
2. Can this type of pressure be replicated by an inline (or some other kind) of pump that increases the pressure? What are the pros and cons of doing this instead of, or on top of, having the storage tank?
3. Why is there another tank inside the loft? Is this to increase supply to the hot water boiler? Why can't this be accomplished with the storage tank on the hill?

Someone gave me advice that each component was put there for a reason, but it would be nice to know if anything can be simplified without sacrificing resilience or efficiency. Is an inline pump plus expansion vessel recommended? Thank you!

Answer 1

The cistern in the house is "traditional UK" as I understand it. Most of my UK friends consider them outmoded. IIRC they were used in part because the municipal supply in many areas was low enough that it would be overcome by lots of simultaneous use, so a reserve in every house meant having water, .vs. not having water when everybody turned on the taps at the same general time of day. Or so I've been told. Presumably a house with it's own well and larger tank got an inside tank out of the pattern "we do them all that way" at the time it was done.

The big one outside insulates you from power outages, pump failures, and drought possibly affecting the supply, and may also help the fire brigade in the event of a fire to be put out. None of which a pump alone is nearly as good at.

I'd consider replacing the in-the house one with a "more modern" solution preserving the full pressure of the outside tank; depending on the pipe size from the outside tank to the inside that might be as simple as connect pipe to pipe, (making sure first all the internal fixtures can handle whatever that pressure is) or it might need a bladder tank.

Unless it's in dire shape and facing expensive repair bills, the big one outside is a thing you should treasure and protect, rather than leap to replace.

Answer 2

The large tank buffers a relatively weak pump or an unreliable pump (wind driven, for instance) to still provide large flow rates until the tank's stored water is exhausted. With your well's flow rate, it sounds like it could be replaced by a combination of high performance pump plus a hydraulic accumulator (assuming that you don't already have the high performance pump).

The attic tank could be an expansion tank for the boiler.

Answer 3

There are two kinds of loft tank:

• a large one (hundreds of litres) which is used for storing cold water for non drinking purposes - to give enough head of water for showers and such when supplied from the street.
• a small one (~10 litres) like a toilet cistern which is the filling and expansion (F&E) tank for a vented radiator system. This sits at the top of the radiator loop - if it becomes low on water (leak from a radiator) the valve will open and add water. It also gives space for water in the system to expand as it gets hot.

The first one holds clean if not potable water, the second holds central heating water that may contain rust inhibitor chemicals.

If you changed your central heating to an unvented system, the loop then becomes pressurized and you no longer need the F&E tank. Otherwise you can't remove it as it's the way the system keeps the correct level of water.

The large cold water tank operates in the way Ecnerwal mentions.