Marine water system

[Jim]

Hi all,

We have a difficult situation with our marine hot water system which I'd like to resolve, but, before ploughing ahead, I need to work out whether what I'm thinking of doing will work okay.

To give a bit of background, our Falcon 22 has three water tanks in total, two cold and one hot (basic, very basic calorifier) The system is not pressurised and the taps operate an ITT pump using micro switches which pushes water out of the taps by pressurising the mid cold water tank. Our current setup is one cold water tank in the bow (the highest tank on the boat) which then feeds into the lower middle cold tank which is situated right next to our hot tank.

To cut the story short, our current calorifier is worse than useless and has no immersion heater option either. We are also very limited on space if we want to fit a replacement unit in the same space and all "off the shelf" modern units are either way too big to fit or so small capacity, there simply wouldnt be sufficient hot water to merit doing it. Here's what I'm hoping will work.....

There is sufficient room to fit a new calorifier in the engine bay but it would mean that the new unit would be higher than the middle cold tank and existing calorifier. Our ITT pump is however, very powerful and produces over 38PSI when operated. My question is this. Would the new tank fill with water okay and also would the heat exchange system with the engine be alright as it would be higher than the existing unit? I think it is possible to fit non return valves to the new tank but what worries me is operating an immersion heater when the tank isn't full

Any advice, thoughts suggestions would be most welcome! We can't operate a pressurised system btw as we would need to start from scratch and it would cost a bomb.

[Antares_9]

Well, the calorifier cannot be empty Jim so don’t worry there, it can only work by the hot water being displaced by the cold and being pushed out of the taps. If you are worried about drain back then a one way valve between the cold tank and calorifier should assuage any concerns. Provided the calorifier’s engine hot water circuit is not the highest point of the whole cooling circuit then it will be fine, if it is higher then you could always fit a swirl chamber to purge any air locks.

[mbird]

Hi Jim

As long as your pump is pressurising the system when a tap is opened to "push" the water out, I can't see a problem, as the pump would pressurise the middle tank which would force cold water into the calorifier, and thereby push the hot water from the calorifier to the open tap. However, going back to the old caravan days when they had microswitches on the taps, some of them used to "suck" the water out of the tank, which I guess would be a totally different kettle of bananas. It might be worth just making sure!

[diesel falcon]

hi,

the only problem i could see in raising the outlet from the hotwater tank would be if it were higher than the tank in the bow,ie it wouldn,t fill by gravity,ie there may be a delay whilst the pump pushed the water up the outlet pipe..I think i would install a preassure pump between the bow tank and the mid cold and calirfior(you could use the old pump and install a preassure switch which would be less money) this would give you a preassurized water system the only part missing is the preassure switch,and maybe a non return valve between the bow tank and the pump feed

just a thought regards trev

agree with others about the engine water jacket conections

[Jim]

Hi Trev,

Fitting an extra pump might well work. I was wondering about the gravity aspect in terms of whether the new hot tank would fill completely which is the reason why I posted up my thoughts (and fears!) here for all to see

I'm assuming your 27 will have the same type of panels in the engine bay with the batteries perched on one side and the other empty. I'm thinking of fitting the new hot tank on our starboard side as there is only the bilge blower fan sitting there at the moment and that can be moved towards the stern which will give plenty of room.

When the boat was first built in 1984, they used nylon "squeeze up" clips instead of jubilee fittings and I found out that all of them were leaking slightly a few years ago. I replaced all but two of them which are below the cabin floor and to change them I'd have to rip up the carpet and floor to get to them which is just too much to do. The existing ITT Jabsco water pump has its own built in pressure switch which works well but because the old hot tank has a pressure relief valve (radiator cap car type), all the pump did was push water out of the expansion tube even with a 38psi cap fitted. The other prob we have with a pressurised system is our galley taps which are also original. I can't find a modern small mixer tap that will fit our stainless steel sink and the existing taps are the type that have a push fit with rubber olives. If you pressurise the system they leak like crazy!

The engine cooling system is my other reservation because the proposed new tank would be higher than the engine and the water pump might struggle to push uphill. Maybe an additional "helper pump" fitted in line might solve the problem.

Thanks for all the input so far

[diesel falcon]

hi,

personally i,d just fit a new ,horizontal calorifier in the engine bay(ours in in there aswell starbourd side ),i wouldn,t worry about the engine conections ,if your stat,s heathy the pump will fill the coil on the calorifier no problem,1/2 inch as aposed to 1.5 inch full flow.Depending on how far you want to go,with the job ,but you could just leave system as is,and just make sure that the calorifiers full(by running the pump)before you used the imersion,

here,s a link to some calorifiers but i suspect you,ll have seen them before http://www.surecal.co.uk/Product/SureCal.aspx ,good luck what ever you decide

[Jim]

Trev, I'm feeling a lot more confident that it will work now. A friend of mine owned the second Falcon 22 that was built and she'd had a new calorifier fitted in the engine bay although not on the shelf that I was thinking of.

Thanks for the link to Surecal (ASAP sell the same things as Hotpots) and they are probably one of the best and most efficient systems money can buy. Their mixing valve is a very smart idea