Waterproof Seiko mods – No Watch is truly water proof. Seiko Mods are just they same, they may be waterproof to a point where the exterior pressure will penetrate the case. So watches like most sealed will will only resist water to a point!
If you’re building custom Seiko mods using aftermarket parts, one of the most overlooked—yet critically important—aspects of your watch is water resistance. At SeikoModder.com, we’ve assembled, tested, worn, and even been diving in the English Channel (its terribly cold) with modded watches, and we’re here to tell you: if your watch is going near water, water resistance matters.
Whether you’re diving into the ocean, relaxing in a hot tub, or just washing your hands, proper sealing is what protects your movement from expensive water damage.
Are Seiko Mods Water Resistant?
The short answer: they can be, but it depends entirely on your parts, your assembly, and your ability to test them.
If you’re creating a waterproof Seiko mod using parts from AliExpress, eBay, or aftermarket suppliers, don’t assume water resistance—even if the listing says “200m WR.” Most sellers only batch-test their cases, meaning that maybe 1 in every 10 or even 1 in a 100 units are pressure tested. That means the case you receive may have flaws in machining or tolerances that were never checked.
So, if you’re:
- Giving away your custom watches
- Selling modded watches
- Wearing them during swimming or water exposure…
…you need a way to test water resistance yourself.
How to Test Water Resistance as a Seiko Modder
Fortunately, water resistance testing equipment can be purchased inexpensively on AliExpress. Most tools fall into two categories:
1. Dry Pressure Testers (Air Testers) – Waterproof Seiko Mods
These use air pressure to test for leaks and are cleaner and more convenient. Popular with professional watchmakers. Good models are available online and they cost over $2000, with no cheaper versions for hobbyists – They have varying test programmes and are fully automated although they don’t offer testing to great depths, in comparison to the tools which they have cloned. They also require a compressor to run so is probably not worth it for a hobbyist.
2. Wet Pressure Testers – Waterproof Seiko Mods
The watch is placed in a chamber filled with air, then submerged in water after pressurising. If bubbles escape, the watch is leaking. These units are often cheaper, as low as $30–$50 + postage.
The Wet Testers on Ali Express were mainly a clone of the Bergeon 5555/98. This is a 6 Bar or 60m test chamber that is no longer in production. The replacement from Bergeon 5555/10 which has a 100m test chamber. It appears on Ali Express both models are now available however when you dig down it appears they are all simply the 60m tester chamber. Some listings suggest the maximum pressure is 100m. Both of these Bergeon machines & Clones are essentially the same, the look the same and have the same manual operation. There is now an electrical wet test chamber available on Ali Express it is an option within the most popular listing we could find that states the maximum rating for the test chamber is 100m.
Pro tip: If you’re making watches regularly, investing in a tester will give you peace of mind and protect your reputation if you’re selling them.
Understanding BAR and Metre Ratings
Water resistance is commonly expressed in BAR or metres (m). Here’s how it breaks down:
| Rating | Equivalent | Use Case |
|---|---|---|
| 3 BAR / 30m | Splash resistant | Washing hands, light rain |
| 5 BAR / 50m | Showerproof | Light swimming (no diving) |
| 10 BAR / 100m | Suitable for swimming/snorkelling | Pool, sea, surface activities |
| 20 BAR / 200m | Dive-rated | Scuba diving, full submersion |
Important: These ratings are lab-based and assume a brand-new watch with perfect seals. Real-world use (heat, wear, impacts) can compromise them over time. Testing is always recommended.
Tips for Buying Water-Resistant Mod Parts
When sourcing parts for cheap with the aim of producing a waterproof Seiko mod watches from platforms like AliExpress:
- Look for sellers that state specific water resistance ratings (e.g., “200m WR” or “20 Bar”)
- Choose cases that include gaskets for the crown, crystal, and caseback
- Buy case + crown + caseback sets from the same seller to mitigate problems with sealing
- Don’t rely solely on listings—verify gasket presence and build quality when you receive the parts
- Always inspect for scratches or machining irregularities around gasket contact points
- Use cases that are designed to use SKX parts – 99.99% of these will work together.
Final Thoughts from SeikoModder.com
At SeikoModder.com, we want every modder—especially beginners—to make watches they’re proud of and confident wearing. Ensuring your Seiko mod is water-resistant is one of the most valuable steps you can take to protect your watch and reputation.
If it’s going in the water, it should be pressure tested.
We recommend:
- Investing in a simple water resistance tester
- Sourcing cases from reputable suppliers
- Checking for proper gasket placement and tight tolerances
- Avoiding water exposure unless you’re confident in your parts and assembly
Have questions about waterproofing your Seiko mod? Check out our other guides or reach out to us directly and we will aim to cover this on the blog.
Disclosure: SeikoModder.com is an affiliate for some of the tools and parts we link to. If you purchase through our links, we may earn a small commission—at no extra cost to you. This helps support the site and keep our guides & info free.
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