I am planning to convert my unused and unconnected forward aluminium water tank so it provides fresh water for my Jabsco toilet flush. The feed pipe into the toilet is 19mm (0.74 inch) internal diameter so I need to have a new connector machined with a 19mm tail.
The current outlet connector on my water tank appears to be nylon and I want to identify the thread size of the section that screws into the threaded tank port. It is circa 1 inch.
Can anyone advise where I can find that thread type and size-my metric thread gauge does not appear to correspond. It is not in my owners manual.
Sean: My recollection is that the fittings on my boat were not metric and is probably why your thread pitch gauge doesn’t fit anything. Someone probably can verify what they are but my guess is NPT (national Pipe Thread)
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
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If it is original to the boat it will be NPT thread. Metric fittings are very hard to find in Canada and the US. As for the fitting itself both ends are threaded, if you are connecting the tank to a hose a hose barb end will make for a much better fitting.
The pitch on the treads look identical so if that is the case it is either 1/2 and 3/4 NPT @ 14 pitch or 1 and 1.25 inch NPT @ 11.5 pitch.
Measurements are “nominal” Here is a link to the sizes
Sean,
Have you considered simply drilling and tapping the tank to the next size up metric fitting? Then you could use a single fitting with a barb end to attach to a hose. Since it is going to be used to flush the head you dod not have to be too concerned about a small amount of metal filings getting int the tank when you drill and tap.
Thank you all for your responses. The info on NPT was really interesting as it is something I had not come across before. I think the fitting is original, the tank is and the fitting was made by Colonial Engineering in the USA. Alas their catalogue does not seen to have it any more.
The fitting came out relatively easily so I went for the easiest option. I originally intended to take the tank out but it was a nightmare on my own-how on earth did they get it in there? We are totally locked down till Easter at the earliest, so I cannot get anyone else to help me shift it out.
For reference - Tracy Tools will supply NPT taps/dies and other North American threads - they are now based in Torquay (UK).
I’ve used them for decades; sometimes picking up items when I am in the UK, sometimes actually sending items to Canada. You might want to keep this in mind should you find that you need to clean or thread a UNC/UNF thread. (please don’t use BSW - sometimes the same diam/TPI, but different thread angle, and IIRC the root and crest are more truncated)
Most of what I do in my workshop is in metric, and some of the metric fine or left-hand taps/dies I just order from TracyTools.
I have removed the original (aluminum) forward water tank on my 30 Ultra (#430) a few times to clean out and repair. Not sure if your configuration is the same, but if you have the double berth in the forward ‘stateroom’ with 56(?) gallon tank under that berth, there should be a couple of retaining boards holding it down that are screwed in thru the surrounding fiberglass frame. If you’ve removed these boards, and removed all but the last bit of water, you should be able to push the tank forward a bit (you may need to disconnect the hoses but it sounds like you’ve done that already) and then lift up on the aft end of the tank. Once the bottom has cleared the fiberglass you should be able to slide it back until the forward end clears and lift out.
Have a towel/dropcloth of some sort on the floor in the forward cabin to protect the floor, and then to stand the tank on it vertically. You can then just gently slide the tank out of the forward ‘stateroom’ on the cloth. I have bi-fold doors separating the ‘stateroom’ from the main salon… the tank just passes by them with millimeters to spare…
some photos attached -
Peter Grabow
S/V CAKE WALK III
1987 30 Ultra 430
Jersey City, NJ
I agree with Peter that the tank is quite easy to remove and you might be advised to remove it to get a good look at the state it is in. My NS30U is ’86 vintage and all the aluminium tanks started to fail about three years. This appears to be a common problem with our boats as INA will sell you a replacement tank made in polythene. You may well find that the tank has several points of corrosion that will quite soon start leaking if they haven’t done so already.
I know all our boats are ‘one-offs’ but I’m fascinated to know how you removed the fittings, as my tank like Peter’s, has its fittings at the forward end which can’t be accessed until the tank is removed.
Bob Illingworth
Nonsuch Luck 30U #367 (GBR1262T)
Moored Brightlingsea, UK cruising the rivers of East Anglia and the North Sea.
Thank you all once again for the information on local sourcing of tools in the UK (what a great outlet Tracy tools appears to be) and getting the tank out/examination.
I think I have a very similar layout to Peter on ‘CAKE WALK III’-thank you for those photos. I can see one difference on the tank layout in that my outlet is at the rear of the tank and my inlet and vent are on the forward end. This is making is difficult to lift out as I don’t have much forward/aft movement. I think I will take out the two forward fittings and that should do it. Some heating pipes are not helping either.
What is the fitting on the top of the tank for?
Once the retaining woodwork was removed, I was able to take the inlet/vent tank off which allowed me to slide the tank forward enough to get my arm down to the bottom of the rear of the tank to under the fitting with a wrench. Once it had budged I could hand unscrew it.
As this is not going to be a drinking water tank, is there any value in painting in the inside-I seem to remember in the Navy the water tanks were painted on the inside with ‘silverine’??
You might look into auto fuel tank repair. Kits are available to reline tanks with epoxy . Usually an cleaning then etching compound and some epoxy. You pour the etching in and slosh it about, then rinse dry and do the same with the epoxy.
This appears to be similar to their rust paint. That product is amazing but you must wear vapour mask when applying and preferably work outdoors. I would not line a drinking water tank. But for a head or fuel tank it will do the job.
With the hose fitting to the pump on the aft end of the tank you can get all of the water out of the tank, but probably some of the sediment that has built up in the tank as well… I have thought about moving the outflow hose to the aft end, but the idea of getting sediment in the line had kept me from doing it.
I am not sure what the fitting on the top of the tank would be used for - as it looks to be the same size as the vent hose fitting, I would guess either a different location for the vent fitting, or possibly for a measurement device that reports the water level.
My mid-ship 30 gal tank (under the portside berth) gave me a very difficult time coming out… and not enough space to reach in and disconnect the hoses or fittings, so I ended up taking a hacksaw to the fiberglass (I thought about this a very long time before doing it), realizing that it would be small enough not to make a difference to the integrity of the fiberglass… it worked very well. Photo attached. You can see the cut outs in the fiberglass on the fore and aft ends of the opening in the fiberglass.
Peter Grabow
S/V CAKE WALK III
1987 30 Ultra 430
Jersey City, NJ
Not sure why you want to epoxy the inside of the tank. Seems like it would be a difficult process to get it uniform and the extra epoxy removed.
If you want an epoxy-coat why not just epoxy-coat the exterior of the tank?
Much easier to do than rolling the tank around and trying to get an even coat on the inside, no?
Then, if you ever decide to use the tank for purposes other than the toilet, you can.
When I had a new fuel tank made, the fabricator epoxy-coated the exterior of the tank. It shows no signs of wear after 9 years.
If you are experiencing leaks with your tank, I repaired the leaks in the forward tank by using a JB Weld product that is safe for potable water tanks. It is a two part putty that one just mixes/folds together, apply over the leaking area (on the outside of the tank) and let dry. Has worked very well and was easy to do. I’m sure you could epoxy over this if you need to.
Peter Grabow
S/V CAKE WALK III
1987 30 Ultra 430
Jersey City, NJ
Ahh ha! That explains the inside the tank method… thank you for improving my knowledge!
That also explains why when I replaced my fuel tank many years ago, and I decreased the new tank measurements ever so slightly after the yard said “the tank came out with barely a millimeter to spare”, that the new tank went in with “the same millimeter to spare” though the dimensions had been reduced… it had the epoxy coating on the outside!
Stay safe!
Peter Grabow
S/V CAKE WALK III
1987 30 Ultra 430
Jersey City, NJ
They coat the inside to prevent further pin holes as well There is a limit to the size the epoxy will span and seal so doing the outside will not work. The next leak will be a doozy …
