Bathtub restoration and repair: how to install an acrylic liner

Recommendation points

• Acrylic liner – subtleties of choice
• Product trimming
• Bath preparation for restoration
• Bonding and sealing
• Finishing touches: siphoning and testing

In just a few hours, you can return the bath to its original appearance and dazzling whiteness. This time we are not talking about enamel restoration, but about installing an acrylic insert. You will learn how to properly trim, seal and glue, and most importantly, how to choose an insert for irregular shaped bathtubs.

Acrylic liner – subtleties of choice

Bathtub restoration with a liner helps to avoid such unpleasant moments as dismantling and moving-out to high floors. But you have to pay for everything, and doubly for carelessness.

The production of liners – stamping and molding of hot sheets of ABS plastic – is a complex and high-tech process. There is a fairly wide range of products that do not meet any wear resistance standards due to the use of plastic of dubious quality or outdated equipment.

The first thing you need to pay attention to is the color of the plastic. At its best, it should be unnaturally white and glossy. Recyclable materials are often put into production: such plastic will give off a gray color, and after several years of operation, yellowness will begin to appear.

The other side of the issue is the thickness of the liner. Unlike glass-fiber-reinforced bathtubs, the liners are quite fragile and falling into the bowl of an eau de toilette can result in a hole. During stamping, the blank sheet is deformed and the wall is always thinner at the roundings. The material remains unchanged only at the edges under the sides, there and evaluate its thickness (must be at least 4-5 mm), strength, flexibility.

It is worth noting that not every company can find an insert suitable for your bathtub. In any case, the best way to find out is to invite a measurer to your place, or send a photo of the molding stamp of the bath to the manufacturer, if you can really get to it.

Product trimming

An acrylic insert is seen as the only adequate way to restore bathtubs that are embedded in the wall on one, two or three sides. In this regard, the liner is inferior even to options with bulk acrylic and enamel restoration, which can stretch for the whole day (or several) against 2-3 hours.

The insert is designed to be installed in a freestanding bathtub, which is then slid against the wall. In this case, the installation takes no more than half an hour. But if tiles are already on the sides, it is more expensive to pull out the bathtub, it is easier to cut the plastic along the line of the walls. Do not worry about ugly cut edges, as they will be covered with a drainage plinth and will be hidden from view. On the contrary, the liner must be trimmed with a gap of 3-5 mm from the wall: the sides do not always sit tightly and bend slightly, which is why the tightly fitted ends scratch the tiles unpleasantly.

The fact of longitudinal symmetry of the bath will help in determining the required undercut thickness. Estimate how deep the bead goes into the wall, determine the exact width of the bath and find out how much the liner is larger than it. You need to cut off at a distance equal to the part of the side embedded in the wall, plus half the difference in the width / length of the bath and the liner.

Please note that the width of the embedded part can vary from the curvature of the walls, so be careful when measuring. It is recommended to give a good allowance when undercutting, and then adjust the liner with an abrasive bar, periodically trying it in place.

After trimming, the liner must be firmly inserted into the bowl as it will stand after gluing, and then with an awl scratch the cutouts of the drain and overflow holes so that they match exactly with the base. Determine the centers of the resulting circles with a compass and make holes with a crown, an offset of a couple of millimeters is not critical here. All cut edges must be additionally machined to remove chips and burrs.

Bath preparation for restoration

The opponents of acrylic liners have a whole arsenal of myths designed to turn the layman away from using technology. It should always be borne in mind that installation by someone else’s hands is performed in order to complete the installation as quickly as possible with a minimum acceptable level of quality. Therefore, the abundance of all kinds of “shortcomings” of the inserts is mainly due to insufficient attention to the details of the installation, because you can put “as for yourself” only for the appropriate fee.

The first detail is the treatment of the bath surface. It must be washed from the remains of soap and limestone, dried and cleaned with coarse sandpaper. The edges of the holes should be treated especially carefully – they should not have any traces of rust, plus the remaining paint should be removed 3.5-5 cm from the edge.

For a tight fit of the sides, so that they do not bend during use, a distance rail should be filled along the contour of the bath. Its thickness must be measured with the liner firmly inserted, usually it is about 20 mm.

The liner itself can also be modified. For example, liners with good wear resistance from primary raw materials can “ache” with thin walls, so the wrong side is pasted over with fiberglass on polyester or epoxy resin in 4-5 layers, or as far as the width of the installation gap allows.

Bonding and sealing

The essence of installing the liner is to apply a continuous layer of polyurethane foam to the bath surface, which, in addition to fixing it, also performs the function of insulating the bottom and walls. In addition to foam, the use of special mastics is practiced. Plus from them – zero expansion coefficient during polymerization and, as a result, guaranteed absence of blisters.

You can often hear that the drain of a restored bath cannot be cleaned with a plunger. This is due to the fact that the silicone used to seal the drain hole is good as a sealant, but as an adhesive it has low adhesion to plastic and enamel. Under dynamic loads, it exfoliates and water begins to seep into the external bath, destroying foam and causing the development of bacterial infection.

This can be avoided if the silicone is applied too much, so that it forms a spot more than 15 cm wide around the ring. But it is better to use high-strength elastic adhesives like SikaBond AT-Metal, or two-component epoxy based compounds. The content of one tube (250-300 ml) is distributed over the two holes with a circular cord with an indent of 15-20 mm from the edge of the hole.

Immediately after applying the sealant, you need to activate the foam by adding the recommended amount of hardener to the balloon. The foam is applied from a distance of 25–20 cm in stripes: first on the bottom, then horizontally on the walls, it can also be applied with a “snail”. The foam layer at the end of spraying should be at least 25 mm without significant differences in thickness and depressions. Most craftsmen use one kilogram cylinder, but practice shows that it is better to take two 750 grams each – this will give complete confidence in the planting density and will make it possible to compact the space under the sides well.

Finishing touches: siphoning and testing

After applying the foam, quickly insert the liner, put the folded blanket on the bottom and climb inside, pressing the plastic with our own weight. It is necessary to press the sides and walls well, remove excess squeezed out sealant and install the siphon as soon as possible. Difficulties usually arise here, because the length of the lag screw is not enough, so pre-stock a longer one, or look for a suitable siphon assembly.

After installing the overflow, the drain is closed and the bath is filled to the brim with cold water. In this state, it should stand for at least 24 hours. 40 minutes after filling with water, you need to press down all four sides with an even rail, usually they are slightly raised by the protruding foam.

After 24 hours, the water from the bathroom can be drained and used without restrictions. Use a non-abrasive acrylic bathtub to care for the liner..