How to prevent water leaking inside,after replacing the batteries.. should i replace the gasket to? after replacing the batteries....

Yes. In your watch, as with most wristwatches that have a snap-fit case back, there's a thin neoprene gasket that sits either in a groove cast into the watch case or around the part of the case back that snaps into the watch case. Either way, the gasket is designed to further reduce the amount of moisture that can wick in between the tiny gap between the case back and the watch body.

As a matter of procedure, for maximum water resistance, this gasket is supposed to be changed every time the watch is opened (for example, when the battery is replaced). As a practical matter, however, I have often reused a gasket if it has not been distorted from pressure or mis-installation (lots of these gaskets end up crimped or pinched when they slip out of position as the case back is pressed into place). Does it provide reduced water resistance? Possibly, though moisture more often enters a watch fastest through the opening for the stem used to set the time. Leaving the back gasket out entirely, however, definitely creates an easy path for sweat and moisture to enter a watch.

The most common failure of a watch to be water resistant is caused by a faulty contact between the case at an opening around the glass, crown, or pushbutton and the opening's gasket. Worn or defective rubber O-rings are often a cause of failure. Condensation forming under the crystal of a watch following a sharp temperature change (a swim after a stretch in the sun, for example) tells you to have the watch checked without delay. This can be an indication of additional moisture elsewhere inside the case. It is also the only water-tightness check a consumer can perform.
Of course non-water-resistant watches don't contain the additional seals and gaskets found on water-resistant models. Consequently, moisture-laden air can easily enter the case. Once inside, a pronounced change in temperature may cause condensation to form under the crystal. Very little can be done to prevent this. A high-quality water-resistant watch, however, properly serviced and maintained, will be sealed to prevent internal water damage and will more than outlast an ordinary watch.
To keep the watch properly sealed, replace any defective parts , such as gaskets, crystals, and crowns. Water-resistant watches should be tested for case tightness at least once a year, as well as every time the watch is opened, such as when a battery is replaced.

1. Place the watch in case holder. Place the watch in the case holder, if you have one. If you do not, place it on a soft cloth.
2. Check for room to work. Check to see if there is room to attach the adjustable case wrench and rotate it 360 degrees. If not remove watch band.
3. Remove case back. Fit the adjustable case wrench into the slots on the case back. Tighten it down until it is snug. Be careful not to slip with this tool as it can scratch the case back of your watch. Work slowly. When it is unscrewed gently pry up the case back taking great care not to damage the internal gasket. If the gasket gets damaged it will need to be replaced with the battery to retain water resistance.
4. Remove battery. The battery will be held in place by some type of retention device. It will need to be removed. Some clips will be removed by using tweezers. Some clips may be moved using a screw driver, and some simply bend out of the way slightly. Remember how it was removed as it must be put back in place exactly for the circuit to be completed after battery change. If the clip is removed, place it and any screws in a paper cup to prevent loss. Remember how the battery was seated, plus (positive) side up or down etc. it needs to be replaced correctly to work.
5. Test battery. Using the battery tester check the battery. If it is dead move to next step, if it is not take the watch to a jewelers for inspection.
6. Clean and inspect battery box. Inspect the battery box the battery came out of. If there is corrosion take it to jewelers for inspection. If there is light dust it may be cleaned with a clean soft cloth.
7. Buy battery. Use the numbers on the battery and buy a new one. Occasionally the number will be obsolete and you will be referenced to a replacement battery in the battery charts. This is the time to also replace the gasket if you need to. Check with a watch maker or jeweler, or the watch company to buy a replacement. We cannot stress enough how important this gasket is to a water resistant watch, without its integrity your fine watch may no longer be resistant.
8. Replace battery. Using the plastic tweezers if you have them, or fingers wearing cotton gloves, replace the battery. Never use bare fingers as finger oils may corrode or short out the new battery. Carefully replace the retention device as it was remove.
9. Replace case back. Make sure that the gasket is in place, and not pinched or caught in the case back when you set it in place. Screw down the case back using your fingers until it is tight and needs the case wrench. Attach case wrench as before and tighten down the case back.
10. Reset and clean watch. Using the appropriate method reset the watch. Use the polishing cloth to clean off any dirt and finger prints.

OR...take to your local jeweler/watchmaker who has the appropiate tools and let them do it for you!!!! :)

The most water resistant watches will have a screwed down case back and crown for maximum water resistance, both of which are backed by internal gaskets. These are the types this articlde will concentrate on. To change the battery in a water resistant watch you will need:

• Adjustable case tool
• Case holder ' + google_ads[0].line1 + '
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• Small screw driver
• Polishing cloth
• Cotton gloves
• Small tweezers
• Plastic tweezers
• Soft clean cloths
• Battery tester
• Paper cup

1. Place the watch in case holder. Place the watch in the case holder, if you have one. If you do not, place it on a soft cloth.
2. Check for room to work. Check to see if there is room to attach the adjustable case wrench and rotate it 360 degrees. If not remove watch band.
3. Remove case back. Fit the adjustable case wrench into the slots on the case back. Tighten it down until it is snug. Be careful not to slip with this tool as it can scratch the case back of your watch. Work slowly. When it is unscrewed gently pry up the case back taking great care not to damage the internal gasket. If the gasket gets damaged it will need to be replaced with the battery to retain water resistance.
4. Remove battery. The battery will be held in place by some type of retention device. It will need to be removed. Some clips will be removed by using tweezers. Some clips may be moved using a screw driver, and some simply bend out of the way slightly. Remember how it was removed as it must be put back in place exactly for the circuit to be completed after battery change. If the clip is removed, place it and any screws in a paper cup to prevent loss. Remember how the battery was seated, plus (positive) side up or down etc. it needs to be replaced correctly to work.
5. Test battery. Using the battery tester check the battery. If it is dead move to next step, if it is not take the watch to a jewelers for inspection.
6. Clean and inspect battery box. Inspect the battery box the battery came out of. If there is corrosion take it to jewelers for inspection. If there is light dust it may be cleaned with a clean soft cloth.
7. Buy battery. Use the numbers on the battery and buy a new one. Occasionally the number will be obsolete and you will be referenced to a replacement battery in the battery charts. This is the time to also replace the gasket if you need to. Check with a watch maker or jeweler, or the watch company to buy a replacement. We cannot stress enough how important this gasket is to a water resistant watch, without its integrity your fine watch may no longer be resistant.
8. Replace battery. Using the plastic tweezers if you have them, or fingers wearing cotton gloves, replace the battery. Never use bare fingers as finger oils may corrode or short out the new battery. Carefully replace the retention device as it was remove.
9. Replace case back. Make sure that the gasket is in place, and not pinched or caught in the case back when you set it in place. Screw down the case back using your fingers until it is tight and needs the case wrench. Attach case wrench as before and tighten down the case back.
10. Reset and clean watch. Using the appropriate method reset the watch. Use the polishing cloth to clean off any dirt and finger prints.

OR...take to your local jeweler/watchmaker who has the appropiate tools and let them do it for you!!!! :)

Take it to a watch shopor jewelry store and they should be able to do it for about $8. If you do it yourself you'll need some specilaized tools to asvoid damaging the watch and a new gasket for the caseback to keep it water resistant. The old gasket cannot be reused even if it looks ok. Once the gasket has been compressed it will leak if reused.

You need either a caseback knife or caseback wrench depending on whether it's a screwdown or snap-on back. If it's a snap-on, you'll also need a caseback presser to put it back on. Using the wrong tools can easily cause damage to your watch. If the watch is "water-resistant" be sure to replace the gasket as well or it will leak - you cannot reuse the gasket. You best bet to do this without having to buy tools, find the correct battery and gasket and risking scratching the watch is to let a watch shop or jeweler do it. Most places will charge about $8 to replace the battery and gasket. Sears sometimes charges only $4 so either way it's worth it. Even though I have the tools myself I usually bring my watches in and have it done since I'd have to go out and buy the battery & gasket anyway.

There is a special caseback prying tool for that purpose. You can find them on ebay for a reasonable cost but you just might want to let a watch shop do it for you to avoid damaging the watch. Also, once you get it off, you have to get it back on which may require the use of a case back pliers designed to prevent damage to the crystal when seating the caseback, You will also want to replace the rubber gasket on the caseback to keep it water resistant. Even if it looks OK, the gasket should not be reused as once it has been compressed and removed it will not seal properly and allow dust and water to enter. Most shops, including Sears, will change the battery and gasket for about $8 while you wait.

The rubber gasket is a water seal and should be trapped between the back and the case. There may be a small rim on the case to locate the gasket.

not being inside your watch to see if water leaks in...it's hard to tell.  However, if you carefully replaced the battery and didn't damage the case or the gasket o ring, things should be fine.  Test it under the kitchen faucet first.