Water Pump

[VADROUILLE]

I have a Shurflo pump that starting to weep in places, i could repair it, but its old and i would sooner replace with new and just keep that as a spare.

I have seen some nice whale pumps and think it will do the job.

The only query i have is the cut out pressure, they do two sorts at 15psi and 45psi.

which cut out pressure is best? i would assume the lower one as the system would be ready at 15psi with less strain?

The pump flow remains the same at 12ltr per minute for both cut out pressures.

We use the showers alot on board dont know if that will influence which cut out pressure i need?

 

[Adamastor]

Go with the 15psi- the 45psi will work, obviously, but is designed as more of a deckwash pump. The 45psi may not be compatible if you have an accumulator fitted in your system.

 

[VADROUILLE]

No accumalator fitted but i have a water heater.

Anybody know what the difference is between the two?

 

[ghostlymoron]

An accumulator is a pressure vessel with an air space which allows the air to be compressed to the operating pressure of the water pump. This smooths out the flow and puts less strain on the pump as it is not required to start/stop so often. Some accumulators have a rubber membrane to seperate air from water, some need recharging frequently as, without a membrane, the air becomes disolved in the water.
A water heater (calorifier?) is completely full of water so cannot act as an accumulator.

 

[VADROUILLE]

An accumulator is a pressure vessel with an air space which allows the air to be compressed to the operating pressure of the water pump. This smooths out the flow and puts less strain on the pump as it is not required to start/stop so often. Some accumulators have a rubber membrane to seperate air from water, some need recharging frequently as, without a membrane, the air becomes disolved in the water.
A water heater (calorifier?) is completely full of water so cannot act as an accumulator.

sorry, worded that wrong, i ment the different prssures on the pumps!

 

[ghostlymoron]

It's the same pump with a different pressure switch setting. The water will come out the same in your shower with both. I'd go for the 15.

 

[VADROUILLE]

How about the prv valve on the water heater? will this affect anything?

 

[ghostlymoron]

Shouldn't think so. The prv is to protect the calorifier against excess pressure caused by the water expanding inside and is less likely to relieve itself with lower pressure. I would check the setting on it.

 

[VicS]

How about the prv valve on the water heater? will this affect anything?

Wont the pump pressure open the PRV if it is higher ?

15 psi will be more than adequate unless you have a power shower on board. Its equal to about 1 bar or 30 ft head. Thats considerably more than a domestic gravity fed shower.

 

[vyv_cox]

Thread partial drift.

Just out of interest I looked up the PRV settings for various calorifiers, although I realise the OP doesn't have one. There have been various posts in the past about PRVs leaking with pressurised water systems. What I found was:

Quick Nautic 600 kPa (= 6 bar, = 87 psi) calorifier working pressure
Isotherm 600 kPa (= 6 bar, = 87 psi) PRV set pressure
Tek tanks 2.5 bar (= 36 psi) PRV set pressure
Ely budget 35 psi working pressure, 3 bar (= 43 psi) PRV set pressure
ATI 4 bar (= 58 psi) PRV set pressure
Vetus 4 bar (= 58 psi) PRV set pressure

Most, but not all, would be OK with the higher pump cutout pressure. Materials of construction makes a difference, all the higher pressure limits are with stainless steel shells.

 

[VADROUILLE]

Thread partial drift.

Just out of interest I looked up the PRV settings for various calorifiers, although I realise the OP doesn't have one. There have been various posts in the past about PRVs leaking with pressurised water systems. What I found was:

Quick Nautic 600 kPa (= 6 bar, = 87 psi) calorifier working pressure
Isotherm 600 kPa (= 6 bar, = 87 psi) PRV set pressure
Tek tanks 2.5 bar (= 36 psi) PRV set pressure
Ely budget 35 psi working pressure, 3 bar (= 43 psi) PRV set pressure
ATI 4 bar (= 58 psi) PRV set pressure
Vetus 4 bar (= 58 psi) PRV set pressure

Most, but not all, would be OK with the higher pump cutout pressure. Materials of construction makes a difference, all the higher pressure limits are with stainless steel shells.

I just fitted the quick nautic boiler, my water system is made of the grey plastic pipe stuff with push connections. i just dont reallu understand what advantage there is if any if i get the higher 45psi pump? it still gives out 12l of water a min as does the 15 psi one.

All i can see the bigger pump doing is putting more of strain on the various pipe connections.

am i reading that right orn wrong?

 

[Strathglass]

it still gives out 12l of water a min as does the 15 psi one.

All i can see the bigger pump doing is putting more of strain on the various pipe connections.

am i reading that right orn wrong?

I would totally agree with you.

I would be very reluctamt to use the pump with the higher pressure switch setting on a boat system unless you had a very specific requirement for it.

Thers is always the possibility of presurizing the calorifier with the high water pressure when the engine is off and the water is cold. Then each time you run the engine enough to heat the water the pressure in the calorifier will increase. This could result in the safety valve opening and dumping some hot water out, especially if you have a copper calorifier.

Iain

 

[vyv_cox]

I just fitted the quick nautic boiler, my water system is made of the grey plastic pipe stuff with push connections. i just dont reallu understand what advantage there is if any if i get the higher 45psi pump? it still gives out 12l of water a min as does the 15 psi one.

All i can see the bigger pump doing is putting more of strain on the various pipe connections.

am i reading that right orn wrong?

Out of interest, why are you going for Whale? The Jabsco units have the new bypass feature, which reduces cycling and means you don't need an accumulator. The Whale info says you need an accumulator.

The Jabsco site also answers your question
Smaller unit, Par Max 1.9 PRESSURE SWITCH - cuts in at 1.0bar (15psi) - cuts out at 1.7bar (25psi) 7 litres/minute (1.5 gallons/minute) open flow

Bigger unit, Par Max 2.9 PRESSURE SWITCH - cuts in at 1.4bar (20psi) - cuts out at 2.7bar (40psi) 11 litres/minute (2.4 gallons/minute) open flow

Depends on the size of the installation I guess - pressure drop will be greater on a big boat.

 

[VADROUILLE]

Out of interest, why are you going for Whale? The Jabsco units have the new bypass feature, which reduces cycling and means you don't need an accumulator. The Whale info says you need an accumulator.

The Jabsco site also answers your question
Smaller unit, Par Max 1.9 PRESSURE SWITCH - cuts in at 1.0bar (15psi) - cuts out at 1.7bar (25psi) 7 litres/minute (1.5 gallons/minute) open flow

Bigger unit, Par Max 2.9 PRESSURE SWITCH - cuts in at 1.4bar (20psi) - cuts out at 2.7bar (40psi) 11 litres/minute (2.4 gallons/minute) open flow

Depends on the size of the installation I guess - pressure drop will be greater on a big boat.

I did not know about that feature on the jabsco ones, as i dont have an accumaltor i would be silly not to buy one of theres i suppose.

i think this is what you have mentioned, and i think it would be ideal for my system (i have two heads and a galley, so 3 outlets)

http://www.tcschandlery.co.uk/5899/Jabsco---Par-Max-2-9--pressure-controlled-pump-12v.html

what do others think??

 

[vyv_cox]

I have the older version of the smaller version, without the bypass feature, with an accumulator. We have to slum it with only one heads but the supply is a little down on flow and pressure when it gets there.