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Flexible water tank questions


Sunflower16

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Sorry if its a really basic question - plus I realise only plasticky boat owners are likely to use the flexible tanks so input may be limited, but looking for advice really - I was aware from the survey that there was some damp /water under the flexible bow tank in the boat - surveyor felt it was not the tank leaking or any issue at all with the hull, but suggested it was likely to be the water filling point at the front of the bow which needed replacing and reseating, and the area dried out as there was no escape for the water.   I thought it might be a good idea to completely drain the tank and remove it, drain any water in the bow and leave it open for some time until everything has dried out before refitting.    If the tank seems undamaged, should I replace it once everything has dried out or should I look at putting in a new one?   Its a standard Vshape bow tank, around 120l capacity.  Unsure of make as cannot see a name, its a royal blue colour as many seem to be. I am unsure how old it is or if/when it was last cleaned out or sterilised.  The sellers installed a new water pump last year but not a new tank.  

Secondly, if I use the boat in the interim without the weight of the tank and water in the bow as ballast, will this be a problem in handling /stability of the boat? 

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We had flexible plastimo tanks on our plastic boat. They were ok for a couple of years, but don't benefit from an inspection /cleaning hatch, so had to be flushed with Milton every year. They also became brittle after a while. We replaced them with rigid tanks. I viewed them as consumables. 

I recall somebody selling water tanks by a hovercraft skirt manufacturer that was supposed to be good. 

The plastic pipes also suffer from muck build up after a while. 

 

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ETA. Also worth checking the o ring is present/in good condition /correctly seated. If it is a plastimo tank

Personally, if it is clean(take the inner bit out and look assuming it is a Plastimo one) and not brittle, i would clean it whilst you have it out and continue using it. 

Edited by rusty69
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I have used this company twice for flexible liners, they make a good product.

One in the bow of my narrowboat and one made for my widebeam which is under the welldeck, that holds 1250 Ltrs.

Better use of the space than the st/steel tank originally fitted by the boat builder.

You can download various drawings of different shapes of tank, put in your dimensions and they will make it to suit. 

https://www.duratank.com/tanks-and-liners

 

 

 

Bazzza

 

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Update to this-  I accessed the bow tank this weekend, drained it and removed it. It was indeed a Plastimo 120l triangular one, but had been lying in a rather manky smallish pool of water for some considerable time given the state of mould and mildew in the area, and on fittings around the bow area.  Although there did not appear to be leaks in the tank, given the state of the cover etc I decided to toss it and invest in a new one.   I hate mould - being a medical professional I have seen some horrible infections and allergies caused by mould, so decided to replace and have ordered one -£56 I think it was.  Until the area is completely dry, though, I am not going to install it.  Luckily the cushions are really well upholstered  -cost a previous owner £750 in 2009 from invoices supplied with boat- and the mildew staining on the undersides has removed well too. 

Left bow locker and the adjacent ones totally open after scrubbing the areas with dettol anti mould /mildew solution.   A previous owner has put two bags of sharp sand /pea gravel in the very front of the bow locker, possibly ballast / bed for the tank?  Have left in situ while its all drying out.  Planning to remove and replace / reseat the water inlet filler so any potential source of leakage is covered.  

I must say I am relieved to have removed that yucky mildewed tank and to have evicted a few slugs (yuck) that were having a party in there.  When its all dried out nicely I thought I might brighten the 50 year old fibreglass up in there with a coat of fibreglass undercoat before installing a pondliner under the new tank.   So far so good. 

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We did ponder over the same thing.......decided they may have "evolved" from eggs which were present in the aforesaid ballast bags (sand and pea gravel stuff)  one of which had broken open and spilled a bit into the V of the Bow........pleased to be able to get rid of them though, they were decidely unwelcome trespassers! 

Edited by Sunflower16
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Well, an update to this issue and a request for advice..... new Plastimo triangular tank duly arrived along with a nice shiny new water inlet filler fitting and I was keen to go and replace the fitting today so at least the bow would be sealed again from the current incement weather.   <sigh>. Its never that simple though, is it?  

I hadn't removed the ply cladding along the inner hull yet and needed to do this to access the filler pipe and the bolts for the filler fitting. Oh dear.......the leak has rotted the two wooden bow V battens /timbers as well as one of the ply sides.   So cleaned up around the area  and removed as much grungey rotten wood as possible before having to quickly close up the area with a tarp as the heavens opened.  

Plugged in a small humidifier to shore power before leaving - it switches off automatically if it collecs more than 1500ml, but am visiting marina tomorrow anyway. Intend taking a small oil radiator (low wattage) to the boat in the next day or two to help dry it out - always used one in the motorhome and it was great for keeping condensation at bay. 

Have decided to do the replacement woodwork myself - female of mature years notwithstanding - it doesn't seem too complex, as its just replacement of the damaged ply plus the two new V-bow battens and I do have some nice tools!    What wood should I use?  6x2 pine?  And how should the wood be fixed to the underside of the GRP foredeck?  Am intending removing any existing bolts etc in the area carefully and sealing up any holes before refitting.  Is it a good idea to add some of that building insulation -the silver one with bubble wrap stuff between the silver sides - behind the ply for insulation?   Hints and tips gratefully received!   

 

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I guess this has moved on to maintenance rather than equipment, but thought I would post here for continuity and in the hope some kindly souls will offer sage advice or even let me know if there are experienced DIYers /carpenters/ joiners who might be able to help - boat is at Barton Marina.  I have attached some photos I took of the underside of the bow where the leak has been insidiously creeping in for who knows how long.....photos taken while lying on my back facing upwards to the underside of the foredeck......have secured the bow front externally from further water ingress with combination of duct tape and tarpaulin /plastic in the meantime, seems to be working!   Its all opened up now and will put a small low wattage oil heater on with the dehumidifier when I return to the boat after work tomorrow.     I thought I might cut away the rotten areas with a multitool until I reach sound wood and see if an infill is feasible.   The 2 front main bow battens (which are really the worst affected) are contoured to the shape of the bow, not sure I can replicate that with my somewhat basic woodwork skills!   

Amazing that all this damage has been from the poor seal around the water filler!    

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Edited by Sunflower16
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