Dont forget lemon juice is like acid on your teeth, so when your sipping it all day your kind of slowly acid etching your teeth. Try to use sensodyne pro enamle to protect them. That is why big pepsi drinkers have weaker enamel. Coke is worse for the teeth has almost double the lemon juice in it.
When we have dry mouth, we are also prone to cavities, saliva protects our teeth, its like a buffer. so dry mouth plus lemon juice over time might add up to some new dental bills.
Have seen pts with dry mouths have cavities as often as every three months, and usually more then one.
So knowing how hard it is on this diet to make things work, stick with the pro enamel, as a procaution. Ask your dentist, he would tell their thoughts for drinking lemon juice in your water all the time.
Dont mean to lecture just trying to save you some $$$$.

Been a dental hygienist for 25 years, so have seen alot of things in my day concerning enamel erosion.
When people talk of bleeding gums, from IP, its not true. The main reason for bleeding gums, besides an injury is PLAQUE.....so brush and floss, keep your pearly whites happy, as well as your pocket book!