Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.
As to what follows:
In response to your question, we say, and with Allah Almighty lies all success:
1. The scholars have two opinions regarding this:
The first opinion: It is not mandatory to change ones padding (diaper) for every wudhu. This is the madh'hab of the Hanbalis, the apparent opinion of the Hanafis [Fath al-Qadir (1/185)] and the Malikis [Hashiyah al-Dusuqi (1/184) and al-Dhakirah (1/29)].
The second opinion: It is mandatory to change ones padding for every wudhu. This is the madh'hab of the Shafi`is.
The correct opinion of the two is the first one, that it is not mandatory for the one who is affected by a constantly leaking bladder or something similar to it, to change their padding with every wudhu. This is so because the Prophet (peace be upon him) did not make it mandatory on the one with istihadhah (constant bleeding or spotting), and because of the hardship and difficulty this would put one into. Ibn Taymiyyah (may Allah have mercy on him) said in his explanation of al-`Umdah [Book of Rulings (p. 492)], regarding this opinion, “…and it is stronger, because in washing the padding every time and drying them, or changing into a clean (pad, etc.), there is much difficulty, as opposed to simply making wudhu. And because, when the Prophet (peace be upon him) ordered her to make wudhu for every prayer, he did not mention washing away the blood and vaginal padding.” And Allah Almighty knows best.
2. According to the opinion that one who is affected by a constant nullifier of wudhu, that they must make wudhu for every prayer, as in the majority of the madh'habs of the Hanafis, Shafi`is and Hanbalis; as soon as the time of prayer ends, or as soon as the next prayers time starts, the wudhu is no longer valid. So it is not valid to make tawaf in this state according to the opinion in which purity (state of wudhu) is a condition or regulation for tawaf. As for what is apparent to me, the wudhu of one affected by a constant nullifier of wudhu does not become invalid during tawaf except by what normally nullifies wudhu, from other than what this person has been afflicted with. So they may continue to perform tawaf even if the time of one prayer ended or the next prayer time began, according to the correct opinion in which tawaf is valid and permissible without wudhu.
And Allah knows best.
Dr. Khalid al-Muslih