Will I accumulate problems without an accumulator?

[jeremyshaw]

Our boat plumbing is fairly standard: Pump, calorifier, Isotherm Basic hot water tank with 220v heater for genset/shorepower use.

Last year the freshwater pump packed up and the accumulator had been giving trouble, so I junked them both and put in one of those new pumps that sounds like a condom - sensormax or something; anyway, variable demand-sensed flow.

I thought "good, I won't need the accumulator to maintain the pressure" which is why I took it out. Then I read in a mag just last week that of course I do need one to cope with hot water expansion - "duh!" I thought now.

BUT we've been running quite happily like this for over a year. I like the new pump which is much quieter but gives additional flow when you want it. The hw tank overpressure valve hasn't dripped. So I'm wondering if with plastic piping etc there is enough 'give' in the system to take up any expansion.

Any views? Will I get problems down the line, and risk bursting a joint, or does anyone else do the same quite happily?

 

[saltwater_gypsy]

Hi Jeremy I have got the same Sensormax pump and think it's terrific. I had an accumulator and fitted it to the hot water tank feed as recommended. The only reason given to fit it there is, as you say , is to prevent drips from the overpressure valve. But----if its not dripping I don't think there is a problem.

Have you got a non-return, check valve in the hot water, cold water feed? If you have short pipe runs this prevents the hot water coming back and mixing with the cold water but it also seals off the hot water tank. If you don't have one then that is a good pressure release route.
Also as you suggest, if you have mainly plastic piping the "give " will help to deal with overpressure.

Blah, blah, blah etc ----- forget about it and sleep tight!!

 

[tcm]

um, i'd stick with what has worked for a year.

Expanison of water in hot weather? Um, well, i see not many wine bottles exploding frinstance? Yes, i would have thought that plastic pipery easily good enough for this. I( also bet the pump wll leak back before blowing things up.

This not at all like water freezing - when the water in each local place of a pipe is locked where it is and then just as it freezes - it expands with nowhere to go, and busts the pipe. Although again - definitely not with plastic pipes.

 

[beneteau_305_553]

I dont have an accumulator and hasn't been been a problem on mine. There is normally enough give in the system pipework to absorb the increase in volume. May be a problem if you have short pipework system and a large calorifier.

The only problem I had was debris getting into the pump and causing it the cycle on and off. Not having an accumulator means it cycles more frequently but for shorter periods. I have now cleaned the pump and fitted a water filter (sureflo strainer) before the pump which has so far worked. The pump only runs when the taps are open and stops as soon as they're closed.

 

[Danny]

"If it ain't broke don't fix it". As well as the flexibility of the plastic piping there's quite likely to be an air space trapped in the top of the calorifier - especially if it's a horizonal cylinder type with the pipe connections at one end. There's usually a small space above the hw outlet pipe which doesn't get filled and will act as an expansion chamber. If the PRV isn't dripping then you don't have a problem.

 

[jeremyshaw]

Thanks for the advice, all. The HW system is servicing 3 heads and a galley, so there is probably about 30m of piping running around the boat to take up the slack. This doubtless explains why I've got away with it. Nice to avoid the accumulator though - one less thing to fix!