Jala Neti is a water cleansing technique or Shatkarma. Yoga works with breathing. When meditating there is a focus on breath, during asanas we keep a flow with breath and with pranayama we control breath to higher prana levels in our body.
Our nostrils are not working even, on some moments the right nostril (sun side) is more active, mostly with activity, and in other moments the left nostril (moon side) is more active, mostly in resting time. This is not working the same for everyone. Like with doing Nadi Shodhana or nostril breathing, it is nice to have both nostrils open. For that, there is this cleansing method Jala Neti which we do with a Neti Pot (as in the pictures below).
The benefits of Jala Neti is not only cleansing the nostrils, it also has a rejuvenating effect which increases the life spam; because we breathe more freely, we can breathe deeper en thus we use less breaths (every living organism has a certain amounts of breaths, when finished, life itself finishes). This technique also helps relieve allergies, colds and sinusitis. When having high blood pressure it is advisable not to do this more than 2 times a week, but normally we can do it twice a day. With regular nose bleedings it is advisable not to do Jala Neti.
The technique is as follows. Use clean water and one teaspoon of salt on one liter of water. First clean the nose. Then check which nostril is most active; test this with the hand or pointing finger under the nose and exhale strongly through the nose. Start with the active nostril, if similar start with the right side. Bring the Neti Pot with salt water to the nose, bend forward like on the third picture. Then tilt your head to the opposite position of the Neti Pot (this is not on the picture), breathe through the mouth, and poor the water through the nostril: it will come out through the opposite nostril. Keep bending forward and blow all the water out of the nose in a tissue (this is possible with Kapalabhati).
After that, never lean backwards or do backward bends, try to do asanas in which you lean forward like childspose. This is very important, because all the water has to come out! If not, this can cause discomforts or even sinusitis.