Disappearing water, please help.

[Clarence06]

Hello, first time poster. Apologies if this is the wrong place to post but getting rather desperate. Currently driving 2006 1.2 Corsa (design)
Got a problem with regards to water. Engine was overheating and water from the tank was disappearing when filled. called the AA and they came and replaced the water pump pipe (original had corroded away, hence no water). AA replaced and did pressure and sniff test, all fine. Car ran fine for a day. Next checked water following morning, had gone down some but not a lot. Driven for and hour in heavy traffic. No increase in temperature. Returned to find water had gone down a little but not much. Topped up again for commute to work, again no problems - however water has again totally vanished when parked. Parked in dry driveway and no evidence of leaks at all both on driveway and around engine.
Anyone any suggestions as not at all car savvy and don't want to be ripped off.
Thanks in advance for your responses and sorry once again if this is the wrong place for posting.
Clarence06

[johnny]

Head gasket maybe, could be the waters evaporating, should be using coolant to prevent this

If your sure its not lts not leaking, it must be using it

[dandadan]

Top up your coolant to the max mark & run the car. Follow all of your hoses to check for leaks. Look under the car to see if you can see any drips. Check your radiator to. Some leaks can be hard to spot

Your expansion tank cap could be causing you to lose coolant. Try replacing with one from a motor factors. They are only a couple of quid.

Check your oil isn't creamy. You can also remove the plugs and check to see if they are 'clean' which can indicate signs of a failing head gasket. Ideally you want your plugs to be brown. Is your exhaust pushing out excessive coolant? Also you can remove the expansion tank cap and start the car and check to see if there's bubbles in the coolant. Quite a few bubbles also indicates head gasket failure.

when you say he did a pressure test did he do it on the full system from the expansion tank?

Is your car hard to start in a morning? Sometimes head gaskets fail between a coolant gallery & a cylinder & when the cars not running coolant is able to leak into a cylinder. Usually the cars hard to start or at least struggles to start then runs abit rough for a minute or 2.

When its running does it sound rough like its mis firing?

Sorry for all the questions lol