I wasn't sure what 1dl is, we don't use that here even though we use metric, but I've just looked it up and it's what I would call 10cl.
OK, that doesn't sound much, but either way orchids are best watered by when they need it, not on a strict schedule of once a week. In the winter that might be too much, in the summer not enough. However at 10cl I think it will generally always be not enough.
Something to bear in mind is that the symptoms you describe could be EITHER underwatering or overwatering. The symptoms are those of dehydration and while that can be underwatering it could also be that overwatering has caused root rot which in turn means that the roots are not good enough to give the plant enough moisture however much you water them.
I'm going to guess from what you have said that you are more likely underwatering than overwatering, but without seeing the roots that's just a guess.
OK, my beginner watering advice is as follows...
Take the pot to the sink, fill the outer pot with water right to the brim. Leave to soak for 10-15min then take the inner plastic pot out and pour ALL the water away. Put the plastic pot back in the outer pot and leave to stand for a futher 10-15min, go back and tip out any water that has dripped in to the outer pot.
Leave the orchid until the medium looks dry again. If there are good roots in the pot they will go dark green when properly wet, and will get paler and paler until they have a silvery sheen, that's when they are dry and should be watered again. Look at the roots IN the pot and at the BOTTOM of the pot, not just those at the top or outside the pot.
If you can't see green roots in the pot then try a wooden skewer. Push it in to the pot right to the bottom (it can stay there all the time so you can use the same hole each time) pull it out when you want to see if it needs watering and if it's damp then wait a bit longer before watering. Wait until the skewer comes out dry.
As you get more experienced you can also judge if it needs watering by the weight of the pot. Feel the weight just after and just before watering. With time you can use the feel of the pot to judge if it is dry yet or not.
Note that there are other ways to water, but this works well for beginners. They can be kept damper than the advice above describes, but to do that you need good air flow around the roots. Techniques such as S/H have them wet all the time, but have an airy non-organic medium. I'm just mentioning this so you are aware that many experienced growers may not use the method above, but it's a good place to start as you get used to them.
The key thing is that Phals actually like lots of water BUT they also like lots of air around the roots. Rot is not caused by too much water as many people think but by lack of air. Too much water blocks the air flow in the medium and leads to rot for that reason. The method of soaking thoroughly, then letting dry fully is a simple way to achieve some sort of balance.
As for the arial roots you have everywhere, I would NOT cut them off. As I have said above the plant likes air around roots and Phals grow arial roots like this all the time. They are just the same as roots in the pot, but more tailored to get their moister from the air. Some people will try and put these in the pot when repotting. Sometimes that is successful but often they will just rot because they are not tailored to be in the pot. I've done it when I had no good roots in the pot, but usually if the roots are otherwise good I just leave them.
Finally, you might consider repotting, you said you have had them a long time, and the bark medium they are in will break down. As it breaks down it can 'sour' and also by just breaking down the air flow can again become blocked and cause problems as a result. General advice is to repot every 2 years with bark. I sometimes go longer, but I find the longer you leave them the more likely you are to suddenly get problems. However a warning is that I've found problems can start when repotting ones that have been left too long, so it's not a definite cure
Linear Mode
