Probably a leak but can't find it

About a year ago I noticed that the water pump motor was coming on for half a second at regular intervals even when no-one was running water. It turned out that I had a leak, a simple drop every 10 seconds, and as soon I got it fixed the water pump stopped coming on.

Recently again, the motor is coming on during the night - usually at about 4 to 4.30 - for about 2-3 seconds now. But it is only happening once a night. I have investigated all areas where I can see or feel water pipes but everywhere is dry.

Can anyone suggest how I can locate this probable leak or what I can do at all, if anything, in this situation?

Check toilets for slight overflow.

Thanks Davy. I will check it out. However, I am 99.9% certain that there isn't one.

Any other ideas out there?

Recently in mother's apartment, there was a tiny drip coming out of the undercounter side of the kitchen tap unit.. Just the tinyest little drip.. found it behind the kick board..

We had a terrible expansive annoying little leak in our rental property.
It literally cost €2000 one year to fix the effects of the leak, without ever finding the leak itself.

The eventually solution after umpteen novenas to the patron saint of plumbing....was a thermographic camera. The cost was €480 for a 1/2 day. We had to leave the heating on for 24 hrs prior to his arrival.

He wandered around with a thing like a video camera, following the pipes.
the pictures identified a number of likely spots and by some miracle the problem turned out to be in the cheapest spot....ie under the decking in the garden. the joints in the pipes just needed tightening. It was a tiny leak but oh so expensive.

I guess this won't work if its a cold water leak though.

I still haven't got to the bottom of this - but here is an update:

If I turn on a tap for about 3 seconds then I hear the pump activitate for those 3 seconds - this is normal. The 'drip, drip' can then be heard while the tank is refilling.

Then, in the middle of the night the pump activates for about 3 seconds in the same way as it activiates when I turn on a tap for 3 seconds. But in this case the tank does not refil. So it's as if the pump has activated but no water has come out of the tank.

So maybe I don't have a slow leak at all but an issue with the pump?

It may be air in the pipework that dislodges over night and slightly moves the flow switch in pump causing it to activate.

Do you have night saver electricity ? Could it be linked to that coming on at night to heat the water ?

No - the water is set to heat up at set times and those times are not concurrent with the pump activating.

As for 'air in the pipes'??? Maybe?? Didn't really understand it.

Putting my head in the clouds on this for now. I'm a little less worried about it when it seems that water is not coming out of the tank at least.

Get the air pressure checked in your pressure tank. This is used in conjunction with your water pump. This pressure tank holds a reserve of water that is used before the pressure switch in the system senses a pressure drop and turns the pump on. If this tank is not re-charged with air annually the pressure tank will become waterlogged leading to involuntary switching on/off of the pump during the night etc. The pressure tank should have standing pressures of either 20psi or 30psi depending on your pump operating pressures.