Engine Cooling problem
1999 Other Peugeot Models Manual 88000 miles

i have a peugeot 306 that started to overheat yesterday. it was discovered that the coolant reservoir was empty due to a leak, i refilled the tank and added Radweld which has stopped the leak for the time being, and the engine has stopped overheating now that the coolant reservoir has been topped up. however, on the couple of short journeys following i kept checking the coolant level, which i had to top up both times with a litre or more of water each time, since there are no leaks i am left with the question where is all the coolant going that i put in before? is it just that it is being distributed around the cooling system and will stop draining the reservoir once the whole system is full of coolant?