Thetford 42178

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  White, for toilets built after May 2015. If yours is bone, or was built before May 2015, this is the wrong number.

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  Bone, for toilets built after May 2015. This is 42179, the bone version of the same kit.

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Compatible models, and the document that says so

• Aqua-Magic Style II

  Verified against Thetford Parts List, Aqua-Magic Style II (Rev D).

• Aqua-Magic Residence

  Verified against Thetford Service Kit instructions, Seat & Cover Kit (Form No. 42100 Rev. B).

  Thetford’s kit instructions cover the Style II and the Residence on one sheet, but the kit contents list four washers marked “Style II only”, so the two are not identical in the box.

Commonly confused with this

• 42036. 42036 is the white seat and cover. 42178 is the white seat and cover for toilets built after May 2015. Thetford lists both on the same current parts list, so which one you need depends on when your toilet was built, not on one having replaced the other.
• 42037. 42037 is the bone seat and cover for pre-May-2015 toilets. 42179 is the bone seat and cover for post-May-2015 toilets.

How to tell which one you have

Two things decide which number you need. First the colour, white or bone. Then whether the toilet was built after May 2015, because Thetford lists a separate pair of numbers from that point. Thetford publishes a serial number location sheet showing where the sticker sits, and the serial number is what tells you the build date.

Is this part still current?

Yes. 42178 is listed in Thetford Parts List, Aqua-Magic Style II, Rev D (11/4/2025), which is the current parts documentation we hold for this model. All four numbers still appear on Thetford’s current Style II parts list, Rev D dated 11/4/2025. None of them is discontinued and none of them supersedes another. They are colour and production-date options within one kit.

Also worth having before you start

• Disposable nitrile gloves

  General guidance for any waste-contact job, not specific to one manufacturer: wear protective gloves and eye protection when you touch anything that has been in contact with human waste, and disinfect your tools and work surface afterwards. If you do not already have a box in the camper, get one before you start.

These are supplies, not replacement parts. We have not matched them to your model, because they do not need to fit anything.

Check this before you order

• Decide colour first: white takes 42036 or 42178, bone takes 42037 or 42179.
• Then check the build date. Post-May-2015 toilets take 42178 or 42179.
• Confirm the model is a Style II or a Residence.
• If your toilet is a Style Plus, none of these four is the right seat.

Before you start the job

Thetford issued a service bulletin, Part No. 42198 Rev. A, about seat and cover kits assembled between 05.01.12 and 08.08.12. It states that improper assembly of kits 42036, 42037, 42178 and 42179 occurred in that window, that pins can fall out and the hinge can come away from the seat or cover, and that this can cause personal injury. Thetford’s instruction is that the problem should not be repaired and the part should be replaced. If your seat is from that window and a hinge is loose, treat it as a replacement job, not a tightening job.

Everything documented for this appliance

• Aqua-Magic Residence — 10 part numbers
• Aqua-Magic Style II — 6 part numbers

We verified the part above from manufacturer documents. The listings below are current eBay inventory, and eBay sellers set their own titles, prices and shipping.

Camper Replacement Parts is not the seller. Price, shipping, stock and item condition are set by the eBay seller and can change at any time. We may earn a commission if you buy through these links.

Where our information comes from

We work from the manufacturer’s own documents. We have not installed this part ourselves, so everything here comes from the documentation rather than from a workshop.

• Thetford Parts List, Aqua-Magic Style II (Rev D), dated 11/4/2025. Published by Thetford Corporation.
• Thetford Service Kit instructions, Seat & Cover Kit (Form No. 42100 Rev. B), dated 02/07/2012. Published by Thetford Corporation.
• Thetford Service Bulletin, Notice of Replacement Part 42036, 42037 (Part No. 42198 Rev. A), dated 08.10.12. Published by Thetford Corporation.

Last checked 2026-08-25.

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