Boiler losing pressure and overflow pipe dripping water

you did not state which model, therefore detailed instruction or remedy is not possible, telepathy do not work that hot as they show in the movies... these two are most "popular " choices in most of boilers, regardless of brand or heating element.

your release valve is blocked by calcium build-up, lift it few times and it should clean and close correctly, if it is not - need removal and cleaning or replacement, cleaning is cheaper...

another reason can be location of the boiler, if it is much lower than lowest radiator - it can constantly overflow and drip hot water from overflow valve as well.

if these two do not apply - unfortunately - with available information, need to call technician or at least relative with plumbing skills...

Contact a qualified heating engineer,obviously leaking probably a split expansion tank,get it checked properly before it causes a n electrical fault.

I had the same problem. There's another clear rubber pipe underneath, that runs from the front right to a pump in the middle. I had to pull it off and dry it with a hairdryer before mine would light properly. Blast into the hole the pipe came off too to dry the sensor if there is one.

Pressure relief valve - replace
The internal seal gets bunged up with dirt & scale and then leaks water [pressure] to that outside pipe
To avoid draining the whole system, turn off the two central heating taps on the 3/4 pipes and then operate the valve manually and / or disconnect - only a small amount of water will escape / drip to below the boiler
Replace valve and fill as before.
If you think your system needs flushing out - now is a good time
Turn off mains electricity to boiler before starting work

If there is no leak anywhere in the system [pipes & radiators] Check the emergency pressure relief valve. It usually is at the base of the boiler and drains to outside [15mm pipe] where, if the valve leaks, water drips can be seen.. Looks similar to the picture with your query
Renew the valve
You can take it apart and clean it but I've never found that to be successful in the long term

If it's from the condenser, it's ok
Should really be piped away but a container under is also ok

Check the pressure relief valve & the pipe to the outside

Your pressure relief valve is open either due to an increase of pressure (that is what it is designed to do) or more likely .the spring in the device is weak and requires replacement . pick one up at Lowes and reinstall the same as removal .You will need a pipe wrench or equivelent and some pipe sealing compound.Hope this helps.

Is your boiler heating your domestic hot water if so i would turn water off to water maker and see if your boiler pressure stays down below 20 psi. If so water maker is bad. The other thing that could cause this problem would be the boiler pump is out.

replace pressure release valve