No water on tank supply? It is almost always the pump, not the water

Every piece of plumbing advice about low pressure or a suspected leak begins the same way: go and read the water meter. It is the foundation of the whole diagnostic method, and it assumes a meter exists.

On a property running rainwater tanks with a pressure pump, it does not. There is no meter, no mains pressure, and no utility involved at all. That removes the standard test and replaces it with a different one, and it means the most common cause of "no water" out here is not the water. It is the machine that moves it.

The short answer

On tank supply, no water is usually the pump: tripped, lost prime, or run dry. Before you ring anyone, check whether the pump has power and whether it is running. If it is running continuously without building pressure, switch it off, because a pump running dry destroys itself and every minute counts against it.

1. Check whether the pump has power and whether the breaker has tripped
2. Listen: is it running, cycling on and off, or silent?
3. If it runs without building pressure, switch it off immediately
4. Check the tank actually has water in it
5. With every tap closed, the pump should be silent. If it cycles, something is losing

On this page

1. The pump is the instrument
2. No water at all
3. Running dry destroys it
4. Cycling with nothing running
5. Finding a leak with no meter
6. Living on tank water

1. Without a meter, the pump is your instrument

A water meter is how everyone finds a leak. Shut everything off, read it, wait, read it again. Movement means water is leaving the system. It is simple, it is definitive, and it is the basis of every leak-testing article you will ever read.

On tank supply there is nothing to read. What you have instead is a pump that is supposed to run only when something is calling for water, and that turns it into a perfectly good instrument if you know what to listen for.

With every tap in the house closed and nothing filling, the pump should be silent and stay silent. If it kicks in periodically with nothing being used, water is escaping somewhere and the pump is repressurising to replace it. That is the tank-water equivalent of a meter that will not stop turning.

2. When there is no water at all

This is where people reach for a plumber first, and where the free checks are worth the most, because the answer is very often something you can establish in two minutes.

1. Is there water in the tank? It sounds obvious and it is regularly the answer, particularly after a dry stretch or with a household that has grown.
2. Has the pump got power? Check the switch and the breaker. A tripped circuit is the single commonest cause of a pump that has simply stopped.
3. Is it running at all? Silence with a tap open means it is not starting. Running with nothing arriving means it is not pumping, which is a different problem.
4. Has it lost prime? A pump that has drawn air rather than water will spin without moving anything.
5. Is there an isolation valve that has been closed? After any previous work, this is worth ruling out before anything else.

Those five cost nothing. If none of them explains it, that is genuinely useful information to give us on the phone.

3. The one thing to do immediately: switch it off

If the pump is running and nothing is arriving, turn it off. Not later, not after you have finished investigating. Now.

A pressure pump is cooled and lubricated by the water passing through it. Running dry removes both at once, and a pump left running dry destroys itself. The difference between switching it off at the first sign and leaving it going while somebody works out what to do is frequently the difference between a repair and a replacement.

The same applies if the tank has run out. The pump will keep trying, and it will keep trying until something in it fails. Switch it off, sort the water out, then start it again.

4. If it cycles when nothing is being used

A pump that starts on its own periodically, with every tap closed and nothing filling, means the system is losing pressure. Something is letting water out, or air in.

• A leak on the line between the pump and the house. On a rural block that run can be long, buried, and entirely invisible.
• A dripping tap or a leaking toilet cistern. Small, constant, and enough to trigger a pump repeatedly.
• A failed non-return valve. Water flows back and the pump repressurises to compensate.
• A pressure vessel that has lost its charge. The pump then cycles rapidly on small demands, which is hard on it.
• A leaking fitting anywhere on the system, including at the tank end.

Telling us which pattern you are hearing, a slow occasional start against rapid repeated cycling, genuinely narrows that list before anybody arrives.

5. Finding a leak when there is no meter

It is entirely doable, it is just done differently, and it is worth knowing what to expect so a quote makes sense.

The pump behaviour tells us there is a loss. Isolating sections of the system tells us roughly where: shut the line to the house and see whether the pump still cycles, and the answer immediately halves the search. From there it is pressure testing and acoustic or thermal location on the section that is losing.

On a property where the house sits well back from the tank or the road, that locating work is worth real money, because the alternative is trenching a long buried run on a guess. It is the same argument that makes relining a drain cheaper than digging it up out here.

6. Living on tank supply

• Know where the pump is, where its isolator is, and how to switch it off in the dark.
• Listen to it occasionally with everything closed. Ten minutes, a few times a year.
• Fix a dripping tap promptly. On mains it wastes water; on a pump it also wears the pump.
• Know roughly how much water is in the tank, rather than discovering it on a Sunday.
• Keep any paperwork for the pump with the house documents, including its age.
• If the property also has an on-site waste system, the two are separate machines with separate failure modes. Do not assume one explains the other.

Anything about the quality of tank water for drinking is a health question rather than a plumbing one, and it is worth asking the people whose field that is.

The short version

• On tank supply there is no meter, so the pump becomes the diagnostic instrument.
• With everything closed the pump should be silent. Cycling on its own means a loss.
• No water at all is usually power, prime, an empty tank or a closed valve.
• A pump running without building pressure must be switched off immediately.
• Running dry removes its cooling and lubrication, and it will destroy itself.
• Leaks are found by isolating sections and pressure testing, and locating is worth paying for.