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Instant water heaters


Kalapattar

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Hi! I’m looking to buy a new LPG gas water heater because flow is slow to the shower to provide hot temperatures! Heater always sounds like there’s not enough water! My pressure tank is about 3 bar 

Which is the best heater for flow rate on a narrow boat please?

Is it the case of ‘the bigger the better? Ta!

Edited by Kalapattar
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Look at the label on the domestic water pump and tell us what it says apart from just "Jabsco". It should have a model name like "Parmax" plus some numbers followed by lpm or gpm and another with bar after it. That  will give us the designed cut out pressure and the flow rate. Thatw ill let us assess if it a pump pressure or flow rate problem.

 

Only an idiot would try to use a shower DRAIN pump (the Gulper) as a domestic water pump because it has no pressure switch on it and it produces pulses of water so I am not sure that you have a clear idea about what does what in your system. Where is this water pump you refer to located in the boat? That will give us a clue to it being the domestic water pump or the shower drain pump (with a bit of luck).

 

 

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When I had a similar issue with my Rinnai instant gas water heater I got a variety of advice here and tried the simplest and most logical, (to me), first.

 

This was to increase the pressure/power/flow, (call it what you will), from the pump.

 

On my Jabsco pump, there is a screw under a blue plastic cover on the end of the pump which adjusts the pressure.

 

I turned it in half turns both ways to identify which way increased the pressure, (can’t remember :( ), and increased it until the Rinnai turned on. It can’t have taken more than 2 or 3 half turns as there would have come a point where I would have decided it wasn’t working.

 

The full make and model of the OPs pump would be good to know.

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The Morco 6 litre is designed to give a temperature lift of 25oC at the highest water flow (5.7 lts per min) or 50oC at the lowest flow (2.7 lts per min) so at full flow if your incoming water is 5oC, you'll only get water at 30oC.  At 5oC incoming water you would probably get about 3.5 lts per min.

If your water pump only gives you 10 lts per min, all the tweaking of the pressure switch will make no difference to the amount pumped. The heater needs a minimum pressure of 1 bar (15 psi) to operate the diaphragm. 15mm pipework is more than adequate for the performance of the heater, Most boat pumps will give you about 25 -30 psi at least, so well within the scope of the heater specs.

As has already been said, a Whale Gulper is totally the wrong type of pump for water supply.

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On 06/04/2021 at 22:07, Kalapattar said:

Hi! The water pump is a jabsco shower/ drain one! Do you recommend a ‘Gulper?

 

 

As the name suggests, your shower drain pump drains the shower and pumps the waste water out of the boat. It has absolutely nothing to do with the pressurised water going to your water heater. As Tony said, you need to look at your domestic/freshwater pump and either see if you can increase the pressure (and adjust any accumulator tank) or buy a new higher pressure pump.

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6 hours ago, Kalapattar said:

Hi! I’m buying a pressurised pump and see how it goes from there. Ta!

 

What is a "pressurised pump"? The words Blackrose were "higher pressure pump". The pump pressurises the water in the system. In the light of the advice Ex Brummie gave it may be an idea for you to get one with a higher output (litres or gallons per minute).

 

See this topic about reading the pump specifications.

 

Edited by Tony Brooks
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7 hours ago, Kalapattar said:

Hi! I’m buying a pressurised pump and see how it goes from there. Ta!

 

Yes just buy any old "pressurised pump"  and see how it goes. If it's the wrong pump then it's fine, you'll only have wasted 100 quid or so. 

 

Or here's another idea: You could actually try to understand and follow the free advice given by experienced people on this forum.

 

Your choice...

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1 hour ago, Kalapattar said:

Yes, advice is to buy a Parmax 2.9

 

I don't recall seeing a Parmax 2.9 mentioned by name and that's after scanning the whole topic again.

 

The 2.9 (as you don't give any units/suffixes could be   gallons per minute or bar (pressure) and from what I can see you have been advised that you may need to increase both cut out pressure and out put volume so unless you tell us the full specification for this pump you may still not solve the problem and maybe waste close to £100, still it's your choice.

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6 minutes ago, Tony Brooks said:

 

I don't recall seeing a Parmax 2.9 mentioned by name and that's after scanning the whole topic again.

 

The 2.9 (as you don't give any units/suffixes could be   gallons per minute or bar (pressure) and from what I can see you have been advised that you may need to increase both cut out pressure and out put volume so unless you tell us the full specification for this pump you may still not solve the problem and maybe waste close to £100, still it's your choice.

Hi! The pump is 11 ltrs per minute and cuts out at 2.7bar

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1 minute ago, Kalapattar said:

Old pump is a drain pump so not suitable anyway!

I do have an accumulator tank, and advert states they’re not required 

 

FWIW I have seen pumps that are marketed as shower drain pumps that seem to have exactly the same internals as a normal domestic water pump. That is multiple pumping chambers and valves. One of this type probably would do the job proving it could reach the pressure. If it were a Gulper (single large diaphragm and two large valves) I can imagine the flame going up and down with each gulp.

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On 10/04/2021 at 12:00, Kalapattar said:

Old pump is a drain pump so not suitable anyway!

I do have an accumulator tank, and advert states they’re not required 

Only just come back to this post. Whatever you do, do not ditch the accumulator. If you do, you will burn out the pressure switch in no time, especialyy if using the Morco at a reduced rate to get hot water.

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