Assuming that you used the bucket of water with the drain, the key should be here in the mud http://img502.imageshack.us/img502/6241/varrocksewers.jpg
bucket of water
you go into the kitchen sewers left of varrok palace and look there its different for each player it should say rusty key
The key is stuck down a drain behind the kitchen in the castle. Go get a bucket or jug and fill it with water at any water source and the sink in the kitchen gives you water (if you did not bring a bucket, up the stairs there is a rooms at the corner and you can get a bucket in there). Use the bucket of water on the drain and the key will be washed into the sewers. Enter the Varrock sewers using the manhole located immediately east of the castle's keep. Follow the north-western path until you get to a stream and go to the small corner. Search for a rusty key on the ground; it will not appear on the minimap. Grab it.
If you're talking about during the quest Demon Slayer, then what you do is use a bucket full of water with the drain, causing the key to dislodge and go into the sewers. Then go near the Church, and there should be a manhole. go down into the sewers, there should be two hallways. go through the hallway to the left, then turn left when you get to the water, and behind a broken wall, with (i believe) skulls piled up, there the key will be :) hope that helps!!!
get a bucket of water pour it down the drain and get it in the sewer go to runehq.com or runescape.wikia.com for quest guides
Assuming that you used the bucket of water with the drain, the key should be here in the mud http://img502.imageshack.us/img502/6241/varrocksewers.jpg
It's Varrock Castle. To get it you need to get a bucket of water and use the bucket of water on the kitchen drain. Thie key will fall into the sewer, you'll need to go to the Varrock Sewers to pick up the key. The key will be on top of a pile of mud near a clump of several skeletons.
bucket of water
you go into the kitchen sewers left of varrok palace and look there its different for each player it should say rusty key
The key is stuck down a drain behind the kitchen in the castle. Go get a bucket or jug and fill it with water at any water source and the sink in the kitchen gives you water (if you did not bring a bucket, up the stairs there is a rooms at the corner and you can get a bucket in there). Use the bucket of water on the drain and the key will be washed into the sewers. Enter the Varrock sewers using the manhole located immediately east of the castle's keep. Follow the north-western path until you get to a stream and go to the small corner. Search for a rusty key on the ground; it will not appear on the minimap. Grab it.
in the drain in varrock place us water in the drainage pipe and then go to the swears to wear the pipe ends
It's on the roof of the gift shop, go to the HQ and talk to G and he will give you the key to the roof then its on the sewer drain on the roof! ☺
The key is stuck down a drain behind the kitchen in the castle. Go get a bucket or jug and fill it with water at any water source; the sink in the kitchen is close and convenient (if you did not bring a bucket, up the stairs there is a room right behind you with a bucket and theres a bucket in front of the drain just outside the kitchen). Use the bucket of water on the drain and the key will be washed into the sewers. Enter the Varrock sewers using the manhole located immediately east of the castle's keep. Follow the north-western path until you get to a stream and search around there. It is just beside the skeletons under a pile of mud. Search for a rusty key on the ground; it will not appear on the minimap. Grab it.
You get the first key upstairs in Varrock Castle by talking to Captain Rovin, you will need to persuade him. The 2nd was washed down the down the drain and you will need to venture into Varrock Sewer to find it. The 3rd is with Wizard Traiborn, who is located in the Wizard Tower south of Draynor. For a full text and video guide please refer to the link below.
sorry you cant make keys on runescape unless of corse it is the crystsal key.
There isn't a key for it unfortunately.