If you're replacing an old bath tub with a new one that will go in the same position, you should be able to use the existing pipe work.  However, if your bathroom remodeling plans involve rearranging the layout of the room and relocating the bath, you'll need to adjust the supply and drainage pipe connections accordingly.  Fitting a bath is done in two stages.  The first step is to put the feet and framework in place, the second step is to connect up the water supply to the faucets and connect the drainage system.

Standard baths come with feet that need to be attached.  The feet and supporting legs are designed to be adjusted in order to keep the bath level on an uneven floor.  Lay out a dust sheet on the floor and place your bath on it upside down.  Then fit the legs into the sockets round the rim.  Usually, they are held in place with a grub screw that goes through the outside of the socket into the leg.

Using nuts, attach the feet in the holes at the base of the legs.  Try to adjust each foot to about the same height, bearing in mind that the height can be altered again when the bath's been installed.  You will probably also be able to screws the leg frames into the base of the bath using the pre-drilled holes in the middle of the leg framework.  When using screws, it's essential not to use screws that are too long, as these might go through the chipboard and damage the actual bath.

Many baths come with an extra supportive leg and foot, which needs to be carefully screwed into the middle of the bath base.  Some more traditional style baths come with ready-fitted feet.  In this case, it may be necessary to place wooden wedges under them to make sure the bath is level, as a level bath is essential for safety as well as for aesthetics.

You can turn the bath back up the right way once you've attached all the legs and feet.  Try to get someone to help you do this to avoid damaging the bath in any way.  You know have to fit the faucets and waste before getting the bath in position and leveling it.  Fitting a pop-up waste to a bath is different from fitting one to a bathroom sink, as a bath waste is operated by a circular handle above the overflow, from which a cable runs to the waste.  You'll need to fit gaskets to the waste outlet and overflow.

Next, screw the second part of the waste outlet into the underside section through the bath outlet.  If you don't have a gasket for this side of the outlet, use silicone sealant instead.  Holding the back section in place, screw the visible section into place on the inside of the bath, making sure you use either a gasket or sealant to create a watertight seal.

Now, use screw fitting collars with rubber washers to connect to attach the overflow pipe between the overflow outlet and the underside of the waste assembly.  Lower the bath faucets into position in their holes and secure with a backnut, remembering to use a gasket or silicone as a seal. 

Gently move the bath into position.  You'll need to use a spirit level and adjust the leg heights several times until the bath is completely level, which can take a while on an uneven floor.  It's critical to ensure your bath is in a secure position.  There are a couple of options here.  One is to cut a channel in the wall to support the extreme edge of the tub.  The other is to attach some support brackets to the wall and bath rim and fit the rim over them.  Once they're in alignment you can screw them in place.

The last part of the installation is to connect the water supply and drainage system, before screwing the bath feet securely to the floor.