This Halacha is an excerpt from our Sefer
Laundering clothing of children:
It is forbidden for adults to launder children’s clothing starting from the week of Tisha B’av. [Some Poskim rule this applies even according to the Ashkenazi custom. Other Poskim however rule that according to the Ashkenazi custom one may not launder children’s clothing during the nine days, starting from Rosh Chodesh Av.] However, those children’s clothing which constantly becomes dirty with feces and urine, may certainly be laundered even the week of Tisha B’av. Furthermore, the custom is to launder all children’s clothing. [Some Poskim rule that this applies to children of up until 2-3 years of age. Other Poskim rule it is up until the age of 3-4. Other Poskim rule it applies at least until the age of Chinuch, which is approximately six-seven years old. Other Poskim rule it perhaps applies until the age of Bar Mitzvah, just as is the rule by Aveilus. Practically, one may be lenient up until the age of Chinuch, which is approximately six years old, and past the age of Chinuch one may be lenient up until the week of Tisha B’av. In years that Tishe Beav falls on Shabbos, then starting from the prior Motzei Shabbos is considered for Ashkenazim to be the week of Tishe Beav in this regard. See Halacha 17F!]
Washing in private: The clothing is to be washed [and dried] in private [i.e. in one’s home rather than a laundry mat, and not in the open view of the public]. [If, however, one does not have the means of washing the clothing in private, or if there is a better washing available in public, then it may be washed in public. Thus, one who does not have a washing machine may wash the clothing in a laundry mat, and if a certain clothing needs dry cleaning it may be sent to the dry cleaners.]
How many clothing to wash at a time: One is not to wash many clothing simultaneously [but rather one clothing at a time]. [However, in a washing machine one may be lenient to wash even many clothing at a time, so long as one is in need of all the clothing to be washed before Tisha B’av, and does not add to it any clothing of adults that cannot be washed.]
Having a gentile do the washing: When one is allowed to wash clothing of children during the week of Tisha B’av, it is best to have the laundering done by a gentile. [Prior to the week of Tisha B’av, there is room to be lenient to allow washing all children’s clothing who are below Bar Mitzvah through a gentile.]
It is forbidden to launder clothing from the start of Rosh Chodesh Av until the week of Tisha B’av, unless one has run out of clean clothing that are changed on a daily basis, or one is washing the clothing of a gentile, or a child, or for the sake of a Mitzvah. During the week of Tisha B’av, it is forbidden to launder any clothing, even if one has run out of clothing, even if it is the clothing of a child or a gentile, unless the clothing is of a child who is below the age of Chinuch, or is needed for the sake of a Mitzvah.
Q&A on clothing of children
May children launder their own clothing?
It is forbidden for children who have reached the age of Chinuch to launder their clothing during the above time period.
If one has the means to buy enough clothing for the children to prevent needing to wash them during the nine days, must he do so?
 551:14; See Piskeiy Teshuvos 551:45; Nitei Gavriel chapter 36
 Michaber ibid
The reason: As although private mourning does not apply to children, public mourning applies to children for either Chinuch purposes or for purposes of Agmas Nefesh. [M”A 551:38; Terumos Hadeshen 152] Seemingly, the practical ramification between the two reasons [Chinuch or Agmas Nefesh] is regarding a child that is below the age of Chinuch, as according to the reason of Agmas Nefesh it would apply to children of any age [see Michaber Y.D. 340:27; Moed Katan 14b; Derisha, brought in Rav Akiva Eiger 340:27; Bach 340] and so is implied in Rama ibid that it applies to even children in diapers. However see P”M 551 A”A 38 who states it only applies to the age of Chinuch. See Nitei Gavriel 36 footnote 8]
 P”M 551 A”A 38 in implication of Rama here; Chayeh Adam 133:18, brought in M”B 551:82, Kaf Hachaim 551:175
 Elya Raba 551:31 in name of Levush, following Rama 551:3 and 4 that we are stringent beginning from Rosh Chodesh Av, brought in M”B and Kaf Hachaim ibid
 Rama ibid
The reason: As such a washing is not done for purposes of Simcha. [Levush 551; Kaf Hachaim 551:178] Alternatively, as they need the clothing and the Sages did not make a decree that cannot be upheld. [Kaf Hachaim ibid]
 Rama ibid states “However those clothing which the children urinate and have bowel movements in, may certainly be washed. Furthermore, it is customary to wash even the clothing of the other children.”
 Chayeh Adam 133:18; Shaar Hatziyon 551:91; Ben Ish Chaiy Devarim 6; Kaf Hachaim 551:179
 Levush 551, brought in P”M 551 A”A 38-39
 P”M 551 A”A 38
 P”M 551 A”A 39 in implication of Darkei Moshe and Beis Yosef; See P”M 551 A”A 38 that at the very least, even the original prohibition written in Michaber must refer to from the age of Chinuch and higher, which is 6-7 years old, as below Chinuch there is no reason to be Machmir.
 Piskeiy Teshuvos 551:45
 M”A 551:39; Elya Raba 551:31; Chayeh Adam 131:18; M”B 551:83; Ben Ish Chaiy Devarim 4; Kaf Hachaim 551:82
 M”A ibid allows doing it by a river even though it is in public and the Machatzis Hashekel and Levushei Serud ibid explain that one is only required to do it in private if he has the ability to do so and the washing quality will be equal to that of the public washing.
 M”A 551:39; Elya Raba 551:31; Chayeh Adam 131:18; M”B 551:83;Mateh Moshe 702; Hagahos Maimanis
Other opinions: Some Poskim rule one may wash even many clothing at a time, such as 4-5 clothing. [Shulchan Gavoa 551:24, brought in Kaf Hachaim 551:177
 Kaf Hachaim 551:177; See Nitei Gavriel 36:4
 Beir Moshe 7:32; Shraga Hameir 6:162; Piskeiy Teshuvos 551:45; Nitei Gavriel 36:4; See Minchas Yitzchak 8:50
 Mahariy Bruno 11; Kneses Hagedola 551:7; Kaf Hachaim 551:178 and 180
 Toras Chaim Sofer 551:30, brought in Nitei Gavriel 36:1, as in such a case one may rely on those Poskim who rule even according to the Rama the prohibition only begin the week of Tisha B’av.
 See M”A 551:38 that the reason for this prohibition is to educate the child; Nitei Gavriel 36:2
Other opinions: Some Poskim rule it is permitted for a child to wash their own clothing. [Maharil Tisha B’av; Rokeiach 310]
 Beir Moshe 7:32; Piskeiy Teshuvos ibid; Nitei Gavriel 36:7