I found this a while back
*Table of Contents:
1. Types of Continence
2. Types of Diapers
3. Determining Whether a Character has an Accident
4. Determining the Severity of an Accident
5. Determining if a Diaper Leaks
6. How to Perform a Diaper Change
7. Consequences for Not Dealing with Bathroom Issues
8. Some Variable Stats (Add-on)
9: List of Diapers and Other Items
10: How to Actually Implement All This Shit
*Types of Continence:
Potty Trained: This person has total conscious control over their bladder and bowel functions and has the hormonal functionality necessary to prevent release of waste during sleep. They do not need to wear diapers, but may still choose to do so out of convenience or cultural influence. Characters with control can automatically tell when they wet or mess.
Bedwetter: This person will usually void whatever fluids are in their bladder if they sleep for more than a few minutes, due to a lack of the necessary hormones for preventing release of urine during sleep. This implies that they still have the conscious ability to retain urine or feces while awake, as if they did not they would likely have incontinence during the day as well. After sleeping, these characters must have their diapers checked or succeed on a DC 10 perception check to notice if they woke up wet.
Bedwetter/bedmesser: Same as bedwetter but the lack of control during sleep extends to the bowels as well. They must have their diapers checked or succeed on a DC 5 perception check to notice if they woke up messy.
Urinary Incontinence: This person has total lack of control over their bladder functions. Urine leaks out randomly, without warning and without the person being aware that it happened. By extension, this person automatically is at risk of wetting the bed while asleep. As their voidings are less predictable, they must have their diapers checked or succeed on a DC 15 perception check to notice if they are wet.
Completely Incontinent: Same as urinary incontinence but the lack of control extends to bowel function. The person will feel the lump in their diaper but will otherwise be unaware of any sensations regarding need to go or preventing the load from slipping out of them. These people must have their diapers checked or succeed on a DC 10 perception check to notice if they are messy.
*Types of Diapers:
Each diaper has 2 parameters that determine the diaper's efficacy in contrast with its effects on the player. A player may choose a different diaper based on the level of protection that they need vs. what they can afford to wear based on pressing circumstances. The parameters are as follows:
1 - Capacity: Determines the maximum amount of urine in mL that a diaper can hold before automatically leaking. Capacity in regards to bowel movements is not generally a factor because nobody poops that much.
This stat will be a flat numerical value in mL with no theoretical boundaries other than that it must be positive. If the fluid volume of the contents of the diaper exceeds this value by any means, the diaper automatically leaks.
2 - Noise: Determines if the diaper is noisy. A noisy diaper will make the player louder and more noticeable, but also typically indicates a thicker and more secure diaper.
Diapers will be listed as "noisy" or "not noisy". If someone is wearing a noisy diaper they have disadvantage on Stealth checks.
Diapers are of course also physical objects that cost money and have weight. Some diapers are also reusable while others aren't but that's self-explanatory. These qualities are laid out as well (See: List of Diapers and Other Items). Reusable diapers need to be washed after each use or they still incur Leaking/Soiling (See: Consequences for not dealing with bathroom issues).
*Determining Whether a Character has an Accident:
Certain circumstances can determine whether a character urinates or defecates. These circumstances are outlined below:
For Potty Trained Characters: Urination and defecation can occur by conscious choice of the player.
For Incontinent Characters (and Bedwetter/Bedmesser Characters at Night): Every hour, the DM will privately roll 1d4 for bladder incontinence and 1d10 for bowel incontinence for each character's relevant potty issues. If the result is 1 on any die, the character will have a bladder or bowel accident that hour (respectively). For example, a bedwetter must not roll any 1's on an 8d4 during an 8 hour sleep in order to wake up dry, but can be treated as potty trained while awake. A totally incontinent character however must avoid the dreaded 1 every hour of every day.
Other circumstances may stimulate accidents, even overriding continence in continent players, such as being frightened or being the target of a diaper-related spell. It is important to note that in these cases, a character may only have a maximum of 1 wetting accident and 1 messing accident per hour unless magically provided with an increased volume of urine/feces to expel. This is to reflect the character simply not having anything to let go, and prevent a character from voiding several times their entire bodily moisture due to running intimidate checks.
Bedwetting or Bedmessing characters, if they wet or mess twice in a row, may wake up unless they either do not care about the accident or have a trait affecting their sleep.
Additionally, characters have Bladder sizes related to their race size and cannot pee more than their capacity each hour unless affected by a relevant status.
Small:300ml to 700ml, Medium:500ml to 1200ml, Large:800ml to 1800ml
*Determining the Severity of an Accident:
For Urine: Roll 4d10. Multiply the result of each individual die to get the volume in mL voided from the character. For instance, a 5, a 7, a 6 and a 4 would mean the character voided (5 x 7 x 6 x 4) = 840 mL of urine. For limits on how much may be wet at once check above.
For Feces: Either they had an accident or they didn't. All fecal accidents convey generally the same effects unless otherwise noted by the DM.
*Determining if a Diaper Leaks:
Whenever a character wets themselves, take the current volume of urine in their diaper and add the amount they just piddled. If that number exceeds the diaper's maximum capacity, it leaks.
Diapers are generally not at risk of leaking due to bowel accidents. Exceptions can be made at DM discretion.
*How to Perform a Diaper Change:
Whenever a player decides that it's time for their character's diaper to be changed, they simply declare that they are changing their diaper. They must also declare what materials they choose to use (what type of diaper they change into, whether they use baby powder/wet wipes/boosters, etc.). The DM will record this information in order to determine the new diaper's capacity and whether the player is at risk of diaper rash.
Multiple players may also elect to change each others' diapers. In this case, they jointly declare who's changing who's diaper. If the two characters are considered to be at least "friends" by the DM, the recipient of the diaper change will receive the TLC buff (treated as having received the effects of a 2nd level Aid spell - +5 current/max HP for 8 hours, non-stacking).