BillP
Senior Member
Please note that this is meant as a DIM (Did It Myself- some will probably say DIM-witted) post and is not meant as an endorsement or recommendation for anyone else to do the same. Pressure vessels are inherently dangerous, and essentially none of the components used in this project were used for their intended purpose. Proceed at your own risk.
While reading Scubaboard I found a link to the post below from a watch enthusiasts' forum. That post describes how to make a DIY pressure vessel for testing the water resistance of watches to 3 bar. I have a handful of puck style dive computers and several dive watches that need periodic battery and o-ring changes, so I thought that I'd give it a try. It was simple! I built the pressure pot in an afternoon (with a few modifications), and it worked great. I thought that I'd share my experience.
Here's a link to the post from 2012 on the Christopher Ward watch enthusiast forum detailing the construction of the pressure vessel. I found it to be an exceptionally well considered and well organized post. Take a look at it before proceeding with my post. Be sure to read the warnings in that post carefully. Thanks to 28800bph for sharing it.
DIY Water Resistance Tester– 3 bar - Christopher Ward Forum
That post's links to the photos of the Bergeon 5555/98 water resistance tester are dead, so here's an example so you can see what's available commercially. The Bergeon 5555/98 is currently priced at $900 on Amazon.com.
The original poster meant for the DIY vessel to be used for testing watches to 3 bar (98 fsw, 43.5 psi) which is apparently the standard for waterproof watches, but the canister is rated for a maximum working pressure of 125 psi (281 fsw, 8.6 bar) so I figured that I could use it for testing my dive gear.
I made several modifications to 28800bph's design:
The only tools that I needed for the project were a pair of pliers to screw in the 1/4” fittings (that I sealed with PTFE tape), a box cutter to trim the size 2 stoppers, a hacksaw to cut the copper tubing, and a pair of scissors and a hole punch to make the rubber straps. I used a 1/4” drill to enlarge the hole in the size 13.5 stopper, but that was optional. I also bought a tube bending tool (Huskey Tube Bending Tool, SKU #1003067559, $12.97 from Home Depot). Like 28800bph says in the post, I could have left the tubing straight, but I needed room for the puck computers. The copper tubing is soft enough to bend by hand, and I have read reports of people filling tubing with sand to hand-bend it without crimping, but I just got the tool to make it easier. I'm guessing that the stainless steel tubing would be hard to manage without the right tool. The copper tubing doesn't look as neat as 28800bph's stainless steel tubing, but it works fine.
Prices have changed a little since 28800bph's post in 2012. Here's my price list from mcmaster.com:
8063K37 Air Fill Valve with ¼ NPT Inlet .......................................................3.94
9151K52 High-Pressure Nickel-Plated Brass Pipe Fitting,..........................5.76
Right-Angle Tee Adapter, 1/4 NPTF Female x Male
4912K2 Miniature Chrome-Plated Brass Ball Valve, Wedge Handle,........5.74
1/4" NPT Female x Male Connection
48435K72 ASME-Code Fast-Acting Pressure-Relief Valve for Air, ..............5.26
Silicone Seal, 1/4 NPT, 80 PSI Set Pressure
9545K137 Rubber Tapered Round Plug, Trade Size 13-1/2, 2-1/4" ............5.21
x 2-15/16" OD, with 1 Hole, Packs of 1
9545K116 Rubber Tapered Round Plug, Trade Size 2, 21/32" ....................8.33
x 25/32" OD, with 1 Hole, Packs of 25
1370N13 Multipurpose Neoprene Rubber Sheet with Certificate, ..............6.43
6" x 6", 1/16" Thick, 40A Durometer
Subtotal for parts (from mcmaster.com) .........40.67
Shipping ...............................................................8.73
Total ..................................................................$49.40
This is the price list from mcmaster.com and does not include the cost of the water filter housing, the copper tubing, the extra ball valve, or the tube bending tool outlined above.
As noted above, 28800bph meant the vessel to be used for testing watches so that they can be pressurized in air and then depressurized underwater to check for leaks (bubbles) without flooding the watch if you don't have a good seal. Most dive computer makers advise against pressurizing their computers in air, but its easy to find reports on the Internet and on Scubaboard of people routinely pressurizing dive computers in air to test them, just like you would test a watch, without causing damage to the computer. This pressure pot design allows the user to choose whether to risk pressurizing a computer in air or risk flooding it in water.
There are threads here on Scubaboard where people discuss other pressure vessel designs. Here are a couple:
Building a Transparent Pressurize cylinder
DIY dive computer pressure test chamber. Under $80
While reading Scubaboard I found a link to the post below from a watch enthusiasts' forum. That post describes how to make a DIY pressure vessel for testing the water resistance of watches to 3 bar. I have a handful of puck style dive computers and several dive watches that need periodic battery and o-ring changes, so I thought that I'd give it a try. It was simple! I built the pressure pot in an afternoon (with a few modifications), and it worked great. I thought that I'd share my experience.
Here's a link to the post from 2012 on the Christopher Ward watch enthusiast forum detailing the construction of the pressure vessel. I found it to be an exceptionally well considered and well organized post. Take a look at it before proceeding with my post. Be sure to read the warnings in that post carefully. Thanks to 28800bph for sharing it.
DIY Water Resistance Tester– 3 bar - Christopher Ward Forum
That post's links to the photos of the Bergeon 5555/98 water resistance tester are dead, so here's an example so you can see what's available commercially. The Bergeon 5555/98 is currently priced at $900 on Amazon.com.
The original poster meant for the DIY vessel to be used for testing watches to 3 bar (98 fsw, 43.5 psi) which is apparently the standard for waterproof watches, but the canister is rated for a maximum working pressure of 125 psi (281 fsw, 8.6 bar) so I figured that I could use it for testing my dive gear.
I made several modifications to 28800bph's design:
- First, the Pentek 158599 Slim Line 10” Clear Water Filter Housing was only available from filtersfast.com (28800bph's recommended source) in packs of 12 for $308 and as singles from Amazon for $35. Pentek makes the similar model 158116 that I bought on Amazon for $16. The 158599 and the 158116 look identical to me and both have a maximum working pressure rating of 125 psi, so I contacted Pentair (the parent company of the Pentek brand) and they couldn't tell me the difference between the two. I think that the Pentek 158116 might have a slightly thicker clear housing (or I screwed my fittings in further than 28800bph did) because I had to twist my fittings 90° from 28800bph's example to get them to fit and function. (My fittings point to the side rather than the bottom of the vessel.)
- I used 1/4” copper tubing instead of 28800bph's recommended stainless steel tubing because it was less expensive and it was readily available in 2 ft straight lengths from my local home improvement store. I also figured that it would be easier to work with than steel. The 2 ft length gave me extra tubing for a second try in case I screwed it up the first time. (JMF 1/4-in x 2-ft Copper L Pipe, Item # 43474, $7.48 from Lowe's.)
- Because I also wanted to also test puck style dive computers and needed more space than if I was only testing watches, I used only one size 13.5 rubber stopper as a space-filler. (I also couldn't find the size 13.5 stoppers in packs of 3 like 28800bph described.) The stopper has a 1/5” diameter hole. It didn't need to be airtight on the 1/4” tubing, so I used a 1/4” drill to enlarge the hole and make it easier to fit the stopper on the tubing. Wetting the tubing a little helped the stopper slide on too.
- I added a second ball-valve between the Schrader inlet valve and the canister to be able to shut off the Schrader valve completely. My bike pump doesn't always make a reliable airtight seal with the Schrader valve. It works well enough to pump up the pressure for a 3 minute watch test, but it sometimes doesn't seal well enough to simulate a longer dive on a computer. Also, the ball-valve on the canister's outlet only works as an on-off valve. (It's easy to test a rapid ascent alarm!) If I want to release pressure more slowly to simulate an ascent on a computer, I have to use the Schrader valve. That means taking the bike pump off, which releases A LOT of pressure from the vessel before the Schrader valve closes if the Schrader valve hasn't been isolated by the second ball valve. Removing the bike pump after pressurizing also allows easier manipulation of the pressure pot. (Accidentally dropping it and having it shatter could be a problem!) The added ball valve makes it easy to remove the bike pump without releasing pressure. I figured all this out after assembling the vessel so I got the second ball-valve from the home improvement store. (Kobalt NPT Mini Ball Valve 1/4-in, Item # 221029, $10.48 from Lowe's.) I wish that I had ordered a second ball-valve from mcmaster.com. It would have been less expensive and better quality, but I didn't want to wait for shipping. (BTW, mcmaster.com was a GREAT source for parts. Good quality, reasonable prices, fast shipping, helpful customer service. They don't tell you the shipping cost until they ship, however.)
- I also used an 80 psi (180 fsw) pressure relief valve instead of 28800bph's 70 psi valve (157.5 fsw) “just because”. This is still only 64% of the vessel's rated working pressure and leaves me a fairly wide safety margin. I could have picked pressure-relief valves with set pressures ranging from 25-300 psi on mcmaster.com.
- I used a neoprene rubber sheet to make straps instead of 28800bph's ECH rubber. I didn't see where the ECH rubber was available, and I don't think it will make much difference. I made 2 smaller straps instead of 1 longer strap to better accommodate different sizes of computers and watches.
The only tools that I needed for the project were a pair of pliers to screw in the 1/4” fittings (that I sealed with PTFE tape), a box cutter to trim the size 2 stoppers, a hacksaw to cut the copper tubing, and a pair of scissors and a hole punch to make the rubber straps. I used a 1/4” drill to enlarge the hole in the size 13.5 stopper, but that was optional. I also bought a tube bending tool (Huskey Tube Bending Tool, SKU #1003067559, $12.97 from Home Depot). Like 28800bph says in the post, I could have left the tubing straight, but I needed room for the puck computers. The copper tubing is soft enough to bend by hand, and I have read reports of people filling tubing with sand to hand-bend it without crimping, but I just got the tool to make it easier. I'm guessing that the stainless steel tubing would be hard to manage without the right tool. The copper tubing doesn't look as neat as 28800bph's stainless steel tubing, but it works fine.
Prices have changed a little since 28800bph's post in 2012. Here's my price list from mcmaster.com:
8063K37 Air Fill Valve with ¼ NPT Inlet .......................................................3.94
9151K52 High-Pressure Nickel-Plated Brass Pipe Fitting,..........................5.76
Right-Angle Tee Adapter, 1/4 NPTF Female x Male
4912K2 Miniature Chrome-Plated Brass Ball Valve, Wedge Handle,........5.74
1/4" NPT Female x Male Connection
48435K72 ASME-Code Fast-Acting Pressure-Relief Valve for Air, ..............5.26
Silicone Seal, 1/4 NPT, 80 PSI Set Pressure
9545K137 Rubber Tapered Round Plug, Trade Size 13-1/2, 2-1/4" ............5.21
x 2-15/16" OD, with 1 Hole, Packs of 1
9545K116 Rubber Tapered Round Plug, Trade Size 2, 21/32" ....................8.33
x 25/32" OD, with 1 Hole, Packs of 25
1370N13 Multipurpose Neoprene Rubber Sheet with Certificate, ..............6.43
6" x 6", 1/16" Thick, 40A Durometer
Subtotal for parts (from mcmaster.com) .........40.67
Shipping ...............................................................8.73
Total ..................................................................$49.40
This is the price list from mcmaster.com and does not include the cost of the water filter housing, the copper tubing, the extra ball valve, or the tube bending tool outlined above.
As noted above, 28800bph meant the vessel to be used for testing watches so that they can be pressurized in air and then depressurized underwater to check for leaks (bubbles) without flooding the watch if you don't have a good seal. Most dive computer makers advise against pressurizing their computers in air, but its easy to find reports on the Internet and on Scubaboard of people routinely pressurizing dive computers in air to test them, just like you would test a watch, without causing damage to the computer. This pressure pot design allows the user to choose whether to risk pressurizing a computer in air or risk flooding it in water.
There are threads here on Scubaboard where people discuss other pressure vessel designs. Here are a couple:
Building a Transparent Pressurize cylinder
DIY dive computer pressure test chamber. Under $80
