There are many reasons why you should replace or install a shower valve, whether you are having drips or worn-out parts that you want to fix with a few inexpensive replacement parts or you want to bring in a new style and features into your bathroom, such as anti-scald protection and preset temperatures. While installing a new shower valve can be a straightforward process, where (sometimes) all you need to have is some basic plumbing knowledge and all you need to do is follow the manufacturer’s instructions, it is not that easy at all times, especially when you will be working with more complicated fixtures, such as the Grohe shower valve. But do not falter—we have here a step-by-step guide on how to install this type of valve.

1. Performing the Necessary Preparations

If you are dismantling an old unit, make sure you turn off the water supply first to your bathroom.
Before you dismantle your old unit, see if the cold water feed is on the right and the hot water feed is on the left, and if not, ask a professional about this.
If you are undergoing major work on your home, then make sure that your water network will be flushed of all impurities, as these elements can damage your mixer.
Prepare your tools, materials and parts with close access to the area where you will be working.

2. Marking the Location

To mark the location of the access panel, punch a hole into the wall behind the faucet by just slipping a long screwdriver alongside the spout nipple of the tub and then push.
In replacing faucets, one has to work inside the wall, with a removable panel in the next room behind the faucet. But if you do not have this access panel, you will be able to install your new Grohe shower valve by cutting a hole in the shower surround, though it is still best to install a paintable plastic panel behind the faucet. You can find it in various sizes, so you can choose one that suits your requirements, at plumbing suppliers or hardware stores near you. But if you do not want to install this panel because it is distracting to the eye, you can instead use an oversized cover plate inside your shower surround. If you already have an existing access panel, but is too low to offer easy access to your faucet, you can place a second one above it.
Do not take measurements to try to position the access hole, but instead, remove the faucet handle or tub spout and then punch a marker hole through your wall. If you have a plaster wall rather than a drywall, then you can use a drill with a long bit other than a screwdriver. However, before you cut a hole that is sized for the panel, cut a smaller hole first to see exactly where your valve and pipes are located. It is only after then when you can position the full-size hole for best access.

3. Securing the Mounts and Connectors

After the holes are properly positioned, screw the S union connectors into the fittings in the wall so that they can extend by about 42 millimeters. Then, screw the escutcheons against the wall.
Adjust the spacing to allow about 150 millimeters between the centers of the escutcheons and then check if they are level. Make some adjustments if needed.
Install the mixer and firmly tighten it, while making sure the nuts are not touching the escutcheons. Verify horizontal positioning and make adjustments if necessary.
Now, you can dismantle everything, but take note of the depth between the wall and the S union connectors.

4. Installing the Thermostatic Mixer

Now, you can seal the thread of the S union connector with the polytetrafluoroethylene (PTFE) tape wrapped in the tightening direction. Tighten the connector with a 22-millimeter open-end wrench.
Adjust the connector to the point where there is a space of 150 millimeters center to center, using the same depth that you have noted on your previous measurements. Determine of they are level with the use of a spirit level.
Apply a silicon seal between the eccentric connectors and the wall, and then screw the escutcheons onto the S union connector.
Remove the blue and red caps from the mixer and make sure that the filters are placed correctly with the rounded side facing inwards. Place the mixer on the connector without any extra seal and then tighten the nuts with the use of a 32-millimeter open-end wrench.
With a spirit level, check if the mixer is level and make some adjustments if necessary. Check for leaks by turning the water supply back on to the mixer.

5. Adjusting the Thermostatic Mixer

To ensure that the thermostatic mixer will be operating properly, you can check the water temperature with a thermometer. Try to see if the 38-degree-Celsius handle guide is lining up with the same temperature on the marker of the shower body. If it does, then you do not have to make necessary adjustments.
If an adjustment is needed, then close the water evacuation outlet and remove the mixer handle cover using a small flat-head screwdriver. Run the water and adjust the cartridge by turning the notched black element to a temperature point of 38 degrees Celsius. Put the handle back with the guide pointing to the same temperature and then screw in the handle and then the cover.

6. Completing with the Finishing Touches

With everything put in place, make sure the hose seal is in the right position and then screw its end onto the mixer. Turn the water supply back on to see of the shower head is properly functioning.

Safety Notes

When removing your old shower valve, makes sure that everything is clean, especially the copper pipes. Sand them off to make sure they are free of burs and solder. You can do this by filing off or heating up the copper to wipe off solder blotches with a dry rag when it runs. Just be careful not to burn yourself and have a spray bottle or fire extinguisher, especially when you are using a torch.