I have a t reg escort ive a header tank that i fill up with water but it empties every time i stop the car and it sits is it the head gasket or water pump

Take off the radiator fill cap.
Top off the radiator.
Crank the engine.

Are there bubbles or is there water spouting out of the radiator fill hole?

Yes: likely cylinder head gasket failure or cracked header.

No: Pressure test cooling system after topping off with a pressure tester. Locate source of leak.

Assuming the water leak isn't anything to do with the non-starting situation, which it probably is though form the sound of it, also check the following:

1) Air filter
2) Fuel filter
3) Manifold Air Pressure sensor.
4) Mass Air Flow sensor.

Blocks crack as well.

Have you tried filling at the motor, header tank or radiator. You may need a new cap or you could have grass or something block the airflow at the front of the radiator, possible head gasket, does it run rough when first started then clear up?

it seems to me your car lost coolant through a crack in the radiator or from the cooling system hoses, which resulted in it overheating. what you can do is pressure test the cooling system to pinpoint the source of the leak and rectify it. it could be anything from a damaged radiator, worn hoses to loose hose clamps. after doing that check to see if the fans are working and if so take your car for a spin. the car should be ok. if during testing the temp goes up then you need a new cylinder head gasket and it could be a bit expensive.

Bad head gasket

Bad head gasket

It may also have been low enough on coolant that one filling wasn't enough. If it is leaking you should see a wet spot or puddle under the car. Also check inside the car to see if the floormats are wet to see if maybe the heater is the source of the leak. Coolant will be sticky to the hand.
Fill the bottle again and run the engine to let it warm up to operating temp. Turn the heater on to its highest settings and the fan as well. Watch the exhaust for signs of white smoke, that is a sign of coolant being burnt off in the engine and that would be a leaking head gasket.Also keep an eye on what is going on in the water tank. If the tank empties out shortly after you start the car, refill it until it stops doing this. That is a sign there was not enough coolant in the engine.
When the engine gets hot you will see likely see bubbling in the tank and probably see thecoolant level drop. DON"T open it now. The coolant is the same temperature as boiling water. Shut the car off and let it sit for 15 minutes or so and slowly unscrew the cap. You will probably get a hissing sound at some point with some bubbling. Stop turning the cap until that stops. Then you can remove the cap and add coolant. You may have to repeat this step more than once but a cuople of times should have the system back to near normal.
Keep an eye on your temperature and water tank for a few days. If the car continues to give you heating problems or using coolant it will need to be looked at to find out the cause. Hope this helps.

ZAS

When car is cold make radiator is full.then fill up your recovery tank make sure you do not spill. then park car on level ground and it dry look for any wet spot's on the ground. If no leak's you have a blown head gasket and if it's useing water that much do not drive it

i have just bought a 52 reg saab 95 3lt v6 filled system with addative yet on a drive the water indicater says low water in system does anyone pls now why and what the solution is