What is it?
This easy mod re-routes the water discharged from the over pressure valve (OPV) so that instead of being dumped in the drip tray and wasted, it will get reused in the machine. The mod is easy to do and doesn’t require any new parts so costs nothing to do.
Newer Mara X machines (confirmed since ~September 2021) are shipped already “modded” by Lelit. So, if your machine is older, doing the mod will make it the same as the newer stock version (see photos and videos below).

Why do the mod?
Earlier versions of Mara X (since release and up to the second half of 2021) dump the OPV discharge water to the drip tray. Re-routing will (a) Reduce water waste; (b) Reduce the water that ends in the drip tray (less often to empty it); and c) Make the machine the same as the newer version that is currently being sold by Lelit.

Is my machine already modded?
To find out – empty the drip tray and put it back to the machine. Put the blind basket (the one without holes that is used for backflushing) in the portafilter and fit to the group. Lift the lever and watch the centre part of the back of the tray. If water is flowing into the tray (when you can hear the pump working) – the machine isn’t modded yet. If you don’t see water entering the drip tray – congratulations, you have a “modded” machine and can go read something else.

INSTRUCTIONS:
The mod is very simple. Once the cover is off and you understand what needs to be done, it can be completed in a few minutes.
The basic idea is this: the machine has 4 clear tubes that currently lead water to the drip tray. We are going to re-arrange those tubes so that one of them (coming from the OPV) will lead to the pump inlet, while the other three stay the same (lead to the drip tray).

Here are the four tubes at the top of the machine (two from the boiler, one from the solenoid valve and one from the OPV valve):

The next two photos are screenshots from a Lelit Insider video, showing clearly how the tubes from the above photo need to be connected (this is the end result, after the mod). This is how Lelit is currently selling the newer version of the machine. You can find the video itself here.

Here us what you need to do:

Remove the top panel and the main part of the case as instructed in @Patrick video here. If you want, you can also remove the panel separating the water tray from the main part of the machine. This will give you better view and access to the tubes and connectors, but the mod can be done without removing that panel if you prefer.
Identify the OPV valve (see pic above). Follow the tube that comes out of it. It terminates in a brass X connector. Disconnect the tube from the X connector and set aside for now. (see below tip for disconnecting the tube).
Looking at the machine from above, Identify the other 3 tubes (2 coming out of the boiler and one coming off the solenoid valve, close to the OPV valve). The two tubes from the boiler terminate in a blue plastic 3-way connector (Y-shaped). Disconnect the two tubes from the blue plastic connector.
The blue connector from step 3 above is now only connected with a short length of tube (a few centimetres) to a 4-way brass connector located right below it. Disconnect this short tube and the plastic connector from the brass connector. You have now freed the plastic connector and the short tube connected to it. Set them aside – they will be used in step 8.
The 4-way brass connector now has two free ports (one where the OPV tube was connected and the other where the short tube from the plastic connector was connected. The other two ports are still connected – one to the tube from the solenoid valve and the other to the tube leading to the drip tray).
Connect the two tubes coming from the boiler (the ones you disconnected in step 3) to the two free ports in the brass connector. First part of the mod is now complete.
Go back to the tube from the OPV which you disconnected in stage 2. Re-route it behind the boiler to the other side of the machine.
Locate the pump inlet (see pic above). It has a tube connected to it, coming from the bottom of the water tank. Disconnect that tube from the pump inlet.
Take the blue plastic connector you freed in step 4, and use the short tube that was connected to it to connect it to the pump inlet. The plastic connector now has 2 free ports. Connect the tube from the OPV to one of those ports, and the tube from the water tank (previously connected to the pump inlet) to the other port. Now both the OPV and the water tank tubes are connected to the pump inlet. The mod is completed.

Test the machine for leaks, put the covers back on and you are done.

Tips:
1. To remove the tubes from connectors you can insert a narrow object (such as a prong from a desert fork) into the tube and work around it to release the tube. The tubes are very strong and you won’t damage them easily.

2. If you find the tubes hard to reconnect, dip them in boiling water for 30-60 seconds. This will soften them and make them easier to slide onto the connectors.

3. If you want, you can replace the 3-way plastic connector with a 6mm 3-way brass connector. This can be T-shaped or Y-shaped – it doesn’t matter.

An even simpler alternative
If you want to re-rout the OPV discharge to the water tank (as done in many other machines), simply compete the first part of the mod (steps 1-5 above). Then, instead of routing the tube from the OPV to the pump, rout it to the water tank. To do this, you will need to cut a small grove in the top of the plastic tank to make room for the tank cover to sit flush.

Disclaimers:
1. If you decide to do the mode, do it at your own risk. Make sure you understand what you are doing. I can’t take any responsibility for any damage or issues you may encounter.

2. Some people reported they hear a change in the sounds of the machine after doing the mod (others, myself included, haven’t noticed it or are not bothered by it. As mentioned before, this is how Lelit now sells new machines, so clearly Lelit doesn’t think this is an issue). I am not currently aware of any reports of issues arising from doing the mod, and as far as I know new machines are shipped “modded” as stock by Lelit.

Credits:
The idea to mod the machine and route the OPV discharge to the pump came from @Patrick . Many others have contributed their experience and insights to the information above. A big thank you to all of them.

Finally, here is a short video showing the connections in my modded machine (note the blue plastic connector connected to the pump inlet is replaced in this video with a brass one):