Plumbing Basics: Installing a Bathtub


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Installing a bathtub isn’t exactly rocket science, but it does require solid plumbing, carpentry, and sometimes, tiling skills.
Replacing an old bathtub with a new one is also a moderately difficult project. If the old tub is readily accessible, the project can move speedily; if you have to open a wall to remove the old tub and position the new bathtub, the task is much harder. In either case, the project is within a home handyman’s skills, although you will need a helper to move out the old tub and set in the new one. Make sure you have qualified yourself for the job and are comfortable attempting it. Rather than hiring a contractor to take over a halfway-completed project, it is better to consider employing one before you begin. Chances are you may need a professional plumber to make tube connections.

This article will help you install a new bathtub in your bathroom if you have already bought a new tub and don’t need to change the arrangement of your previous water supply pipes.

Your tools and material checklist should comprise the following:

  • New Bathtub
  • Hammer
  • Pipe Wrenches
  • Prybar
  • Safety Glasses
  • Level
  • Pliers
  • Adjustable Wrench
  • Putty Knife
  • Screwdriver
  • Cold Chisel
  • Tape Measure
  • Pipe Caps

Preparing for the Installation

Firstly, the supporting frame supplied with the bath should be fitted (if required) according to the manufacturer’s instructions.

Next, fit the taps or mixer to the bathtub. When fitting the tap block, it is important to make sure that if the tap comes with a plastic washer, it is fitted between the bath and the taps. On a plastic bath, it is also sensible to fit a supporting plate under the taps unit to prevent strain on the bathtub.

Fit the flexible tap connectors to the bottom of the two taps using 2 nuts and olives (sometimes supplied with the tub).

Fit the plug-hole outlet by smearing mastic filler around the sink outlet hole, and then pass the outlet through the hole in the bath. Use the nut supplied by the manufacturer to fit the plug-hole. Examine the plug-hole outlet for an inlet on the side for the overflow pipe.

Next, fit the end of the flexible overflow pipe to the overflow outlet. After that, screw the pipe to the overflow face which should be fitted inside the bath. Make sure you use all of the supplied washers.

Connect the trap to the bottom of the waste outlet on the bathtub by winding the thread of the waste outlet with silicone mastic or PTFE tape, and screw on the trap to the outlet. Connect the bottom of the overflow tube in a similar manner.

The bath should now be ready to be fitted in its final position.

Removing Old Taps

If you need to replace old taps with new ones as a part of your installation, then the first thing you should do is disconnect the water supply. After doing so, turn on the taps to drain any water remaining in the system. The process of removing the existing taps can be quite problematic due to the restricted access that is often the case.

Use a basin wrench (crowsfoot spanner) or a tap tool to undo the nut that connects the supply pipes to the taps. Have a cloth ready for the remaining water that will come from the pipes. Once the supply pipes have been removed, use the same tool to loosen the nut that holds the taps onto the bath/basin. You will need to stop the single taps from turning during this process. Once the taps have been removed, the holes in the bath/basin will have to be cleaned of any old sealing compound.

Before moving on to fit the new taps, compare the pipe connections on the old taps to the new taps. If the old taps are longer than the new taps, then a shank adapter is required for the new taps to fit.

Installing the Bathtub

Using the two wooden boards under its feet, place the bathtub in the required position. The wooden boards are helpful in evenly spreading the weight of the bathtub over the area of the boards instead of focusing all the weight onto four small points.

The next goal is to ensure that the bathtub is leveled all round. This can be achieved by checking the spirit level and adjusting the feet on the bathtub until the spirit level reads level.

To install taps, fit the bottom of the furthest flexible tap connector to the appropriate supply pipe by making a compression join; then do the same for the other tap.

Switch on the water supply and check all joints and new pipework for leaks and tighten them if necessary. Fill the bathtub and also check the overflow outlet and the normal outlet for leaks.

Finally, fix the bath paneling as described in the manufacturer’s instruction manual.

Tiling and sealing around the bathtub should wait until the bathtub has been used at least once as this will settle it into its final position.

Fitting New Taps

If the tails of the new taps are plastic, then you will need a plastic connector to prevent damage to the thread. One end of the connector fits on the plastic tail of the tap and the other end provides a connection to the existent supply pipes.

If you need to fit a monobloc, then you will require reducing couplers, which connects the 10mm pipe of the monobloc to the standard 15mm supply pipe.

Next, position the tap in the mounting hole in the bath/basin ensuring that the washers are in place between the tap and the sink. Secure the tap in place with the manufacturer provided backnut. Once the tap is securely in place, the supply pipes can be connected to the tails of the taps. The taps can either be connected by using corrugated copper piping or with normal tap connectors. The former type should be connected to the tap ends first, tightening only by hand. The supply pipes can later be connected to the other end. Tighten both ends with a spanner after both ends have been connected.

Tiling Around the Bathtub

In the area where the bath meets the tile, it is necessary to seal the joins with a silicone rubber caulking. This is important as the fitting can move enough to crack a rigid seal, causing the water to penetrate the wall between the bath and the tiling, leading to complications with dampness and possible leaks to the ceiling below.

You can choose from a variety of colored sealants to blend in your fixtures and fittings. They are sold in tubes and cartridges and are capable of sealing gaps up to a width of 3mm (1/8 inch). If you have a larger gap to fill, you can fill it with twists of soaked newspaper or soft rope. Remember to always fill the bathtub with water before sealing, to allow for the movement experienced when the tub is in use. The sealant can crack fairly early if you do not take into account this movement before sealing.

Alternatively, ceramic coving or quadrant tiles can be used to edge the bath or shower tray. Plastic strips of coving, which are easy to use and cut to size, are also easily available on the market. It is advisable to fit the tiles using water-resistant or waterproof adhesive and grout.

Maybe what your home needs is not an extreme makeover, but some improvements in bathrooms. Let's take a look! Why replace if you can save money refinishing? We can repair and resurface all types of baths, basins, showers, tiles, backsplash, cabinets & benchtops. Contact us at 210-858-6207

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