Denizen of the Deep

Thank you David. I think I had a bit of a technical issue there... The story with that butyl bag was that it failed after only a year or so. Found it swimming in water in the bow cavity. I suspect that one of the welds around a fitting had failed. The remedy was to remove the bag, write it off as a well intentioned failure, and ask the great guys at Candle Bridge Fabrications (now based at Braunston Marina) to clean out the integral tank and paint it with a food-grade epoxy paint. The tank is now in service again at full capacity. Modern boats seem to be built with cuboid stainless or plastic tanks, offering lower capacity but vastly improved quality, reliability and accessibility (usually slotted under the foredeck, I think), and that's what I would look for in a new boat. For integral tanks, butyl liners seem dody and tricky, and cleaning and painting (to protect the inside of the hull) seems the best choice to me. Again, apologies for the inadvertent radio silence and thanks for the interest shown! :)

After a false start when I inadvertently twisted the liner when tightening the outlet nozzle against the bulkhead, the water bladder is now correctly located and connected. Here it is filling up. Meanwhile the pleasure of running water is restored to nb Flag Iris after three months of living out of bottled water. You don’t know what you’ve got till it’s gone!

My new water tank bladder took about 4 weeks to manufacture. They used the fittings salvaged off the old liner so that re-fitting to tails will be straightforward. On a fine morning, we decided to fill the liner outboard and make sure it's watertight. So far, so good.

It seems as though the material is indeed certified by WRAS for contact with human consumption water. It's nylon-textile reinforced EPDM 1.25mm thick sheeting. I took my old, punctured tank liner to their factory and we discussed how they were going to produce a bag to similar shape, and the aluminium skin fittings they'll use to pass the inlet, breather and outlet tails. Manufacture time is about 4 weeks. It's a bit of a drag living out of bottles, but tolerable as we're on a marina berth. Probably going to have to do a bit of hole enlargement in a steel bulkhead to accommodate a slightly higher outlet pipe, but otherwise can't wait to get the new liner fitted!

Update: I've had a quotation for making a custom bladder from a reinforced EPDM material from Butyl Products Ltd of Billericay, using the old leaking liner as a shape template. Am now in the process of double checking suitability for potable water use before going ahead with manufacture.

Thanks for joining the conversation! Yes, I'd thought about that. The thing is, the outgoing (leaking) bladder tank was actually just so simple, and I feel really reluctant to install a more complicated (e.g. linked tanks) system until I really have to! With linked tanks I guess I'd need to be introducing another two or three 'weak' points (junctions) into the whole system, and adding complexity rarely feels good. Still, considering all options, so thanks

I just spoke to Sam at Tilley regarding the products on https://www.tidel.biz/flexible-tanks/ She explained they are only really able to make the 'pillow' tanks (top picture) to custom specs, and not -- disappointingly -- what she called the '3D' tanks pictured at the bottom of the page and which are the sort I had in mind that could make best use of a narrowboat well deck space. Anyhow, think I'll measure up and draw the space I have to play with and see if there's a 'pillow' configuration that might work.

Good work, Robbo! That does look very interesting.

Yes, so it seems... Thank you.

Thanks for your reply, Furness Yes, Duratank may have been the only show in town, but now they're out of it and concentrating on their hovercraft business, I think. I've seen some 'off the peg' bladder tanks such as https://www.tanks-direct.co.uk/160-litre-flexible-water-tank-potable.html . Issues I see with these are that they don't make the best use of all the available (non-cuboid, non-triangular) space, and may need some imaginative seating to keep them from sloshing, moving around and tugging on the port fittings when the boat's in motion, smashing into lock gates etc!

Grr! The big bloated flexible water tank liner in the boat I bought three years ago sprang leaks in a few places including, apparently, around the inlet port and filled the bow cavity with water that was luckily contained there and which I spent an energetic morning bailing and pumping out. The bag seemed to be the custom shaped type designed to fit the space in my Liverpool boat quite well. A previous owner had used 1" thick polystyrene slabs to seat it on and insulate it, I guess. I called Duratank of Southampton, who may well have made this leaking tank, only to find that as from September this year they are no longer making these custom tanks as "it's no longer profitable". I don't think I want to look at repair not least because I can't see how you'd remedy a leak round a port, and also because the liner may be up to 15 years old already and a replacement of some sort seems wiser. * Does anyone know of companies still manufacturing custom-fit flexible drinking water tanks? * I may need to look at rigid plastic tanks too, but I haven't got much of a hatch space to fit one through and it might mean cutting a slightly wider hatch in the deck.

Two years ago a pilot from Portishead to Sharpness cost about £150. I only attempted it after I'd had my boat nearly a year, had addressed an intermittent fuel supply issue, felt that I knew what she was capable of, got trained and qualified on VHF radio in case of serious breakdown, and found another boat to travel in convoy with. Even then, I didn't have as much engine power to spare as I would have liked. And yes, it was daunting, all the way. In your deck shoes I'd take the canal route or hire a crane and truck!

Thanks very much for all your thoughts and replies. Re-thinking

Hey boaters. My boat has a Mastervolt 12-2000-100 mass combi unit and a 70A alternator charging the service batteries. The Mastervolt's 'smart' 3-phase charger requires mains level voltage to operate. I am wondering whether it's possible or worthwhile inserting some gizmo between alternator and Mastervolt so that the Mastervolt can be offered high voltage from the alternator (some kind of transformer?) that will trigger its smart charging function and save me some engine running time when recharging batteries. Any ideas?