Masaail pertaining to water and wells

Q: Can we use solar water heaters?

Q: I had learnt in madressa that we must cover food, etc before sleeping because of sickness. My question is regarding water that is collected during the day and night and is left uncovered. Can it be used for wudhu?

Q: If any bird dies in the water tank, is it permissible to use that water for bathing and washing clothes etc?

Q: In water which is more than 10×10, if something taahir falls inside making the colour, taste and smell to change (e.g. Leaves fell in a large swimming pool), is that water taahir? Can it be used for wudhu and ghusl?

Q: If ghusl becomes obligatory and one takes ghusl from a bucket of water, will the water become mustamal even if hands are washed before putting it into the bucket? I have read that the water becomes mustamal only when the hands are not washed before putting it into the bucket.

Q: Please help me, I have a quite bad waswasa wudu issue and i'm stuck on this fiqh problem, I know the problem looks quite long, but if you could help me, it would make my life easier, please. 

In the hanafi madhab, I have read two slightly different interpretations that when does water become Musta'mal water (used water). I have included several examples so you may understand my issue.

OPINION A) Water becomes used when water leaves the BODY

OPINION B) Water becomes used when water leaves the LIMB

To me, this is a distinct difference.

In my wudu following OPINION B, washing my feet has been difficult, due to what I call a boundary issues ie Water may land on the wrong limb (e.g LEG) during washing and flow onto the limb being washed (e.g FEET)-in which this water has now become Musta'mal as it has left the limb (LEG) and gone to a different limb (FOOT). 

EXAMPLE 2 ie water lands on slightly above the ankles (leg) and flow onto the ankles-using opinion B this would be Musta'mal water on my ankle instead of purifying water

EXAMPLE 3 for the face- to ensure I wash the entire face, the washing exceeds the boundaries of the face to ensure that the entire face is washed.

This means that I end up having Musta'mal water on my hands which I need to deal with before I wash my face for the second and third time.

EXAMPLE 4 Same for arms, the elbow and upper arm.

So my wudu is taking longer than it should, I could follow OPINION A, this would mean that if water flowed from just above the ankle (leg) onto the foot, this water would still be purifying however, I am nervous my wudu would not be valid because of Opinion B.

Can you help me?

Q:

1. A person who has disability is unable to raise the feet up to the sink basin for wudhu so she gets a bucket of water, takes water from the bucket puts water on the right foot with the hand and the mustamal (used) water falls in the same bucket which has clean water, then she uses the same water for the left foot, the question is if musta'mal and clean water mixes together can it be used for washing the left foot?
2. In the above situation is the wudhu valid?
3. If the wudhu was not valid does the salah have to be repeated, which was prayed with the washing of the feet with mustamal (used) water and clean water mixed together?

Q: I have a small well in my home called borehole. Recently i've come to know that the water changed it's smell and this is due to maybe the outside line of guter/drain is mixing in the well water although the well is quite deep almost more than 40 feet. What would you advise as per the water? Has it become impure or can it be used for bath and other purposes?

Q:

1. What is the ruling with regards to water in a bath tub. The moment one steps into a bath tub, is the water considered as maaul musta'mal, thus ghusl will not be valid with such water! Is this correct? 
2. Is it true that water should not be able to seep through ones mozas? Is it correct?
3. What is maaul musta'mal?

I would appreciate 5 references to each answer.

Q:

1. How much water must a swimming pool contain in order for it to be considered paak if najaasat falls in. Should one measure according to  5m x 5m x 5m ie. according to volume?
2. Will chlorine and other chemicals purify the water and thus render it paak or not?
3. If clothes are washed in a washing machine, must the clothes be washed in 3 cycles of a rinse and spin?