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Discussion Starter #1
The Islander Freeport water pump (original 1978) that comes with the boat we have is rated at 2.8 gal a min. That is for house water.
We are looking to replace ours as it is way too noisy.
We would like one as quiet as possible.
We also have a pressure tank.
There are a couple on the market we re looking at.
• I am wondering if we could up the gal a minute without busting water lines?
• Would there be an advantage to upping the gal per min?
• Would it make a nicer shower etc?
• The pump we have now seems to work fine enough
• Downside is we would use more water?
• We are also going to get a wash down pump so this will be used strictly for fresh water.

2.9 gal min
Jabsco 31600-0294 'Par Max 3' pressure-controlled pump
http://www.jabscosh op.com/marine/ pumps/pressurise d-fresh-water- pumps/31600- 0294-par- max-3-pressure- controlled- pump.htm

3.0 gal min
Aqua King™ Standard 3.0 (12 VDC) 3.0 GPM [11.35 LPM]
http://www.shurflo. com/pages/ Marine/marine_ categories/ potable/potable2 .htm

Thanks,
Chip
ELEGANT'SEA IF36B #29
 

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When they demo'ed the facilities here at the marina, I upped mine from a 3gpm to a 5gpm pump, I made sure all the lines were in good shape

So;
1. I haven't burst any lines yet ( almost a yr now )
2. that's a judgement call on your part
3. Yes, our shower kicks a$$ ( even has a massage head thing on it )
4. Again, a judgement call on your part
5. Yes, you probably will use more,

Downside is my our water heater is only 6 gals


Be sure to check the rating on your relief valve on your water heater to see how many psi it's rated for
 

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GPM = volume.
Lines burst from pressure--not volume.

So if the new pump puts out higher volume but the same pressure, there's no danger. Either the rest of the system can handle the extra volume, or it will choke it back. For instance, if you have a 1.5GPM shower heard--it will only pass 1.5GPM regardless of the pressure. But having a pump with higher volume might allow you to use the shower and galley at the same time without the water dribbling.

To some extent, hose diameters and fittings and the length of the hose runs will all limit the amount of volume the system will handle, and the capacity of your pressure tank will factor in as well. Bottom line is that you may see some improvement in flow, and there should be no risk as long as you're not going from 2.9GPM up to something like, say, 100GPM.<G>
 

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Small correction

Yes, lines do burst from the pressure. However if the line size remains the same the pressure must increase to deliver more volume. To put it another way, the line size causes the resistance to flow. To get more volume (gpm) the pressure must be increased to overcome the same resistance. It is very analogous to DC electric circuits: Voltage is the pressure, current is the volume, and resistance opposes the flow. You can push more flow thru the resistance by increasing the pressure.

GPM = volume.
Lines burst from pressure--not volume.

So if the new pump puts out higher volume but the same pressure, there's no danger. Either the rest of the system can handle the extra volume, or it will choke it back. For instance, if you have a 1.5GPM shower heard--it will only pass 1.5GPM regardless of the pressure. But having a pump with higher volume might allow you to use the shower and galley at the same time without the water dribbling.

To some extent, hose diameters and fittings and the length of the hose runs will all limit the amount of volume the system will handle, and the capacity of your pressure tank will factor in as well. Bottom line is that you may see some improvement in flow, and there should be no risk as long as you're not going from 2.9GPM up to something like, say, 100GPM.<G>
 

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Usually, there is a switch on the water pump that turns off the flow of water when it reaches a certain pressure. Usually this switch is adjustable by you the owner, although it usually comes preset at a reasonable level from the factory. If your pump is rated for 2.5 gal per minute it is able to move 2.5 gallons of fluid in 60 seconds. It will do so until the pressure exerted by the fluid on the switch exceeds the level the switch has been set for.

Your pump will not burst your lines unless you set the switch to only turn off at a level that exceeds the capacity of the lines.

i.e. If your lines are rated to handle 75 PSI and you set your switch to 80 PSI, and there is no pressure relief (like an open tap) then your liines will burst.

If you do not set the pump switch higher than the rated capacity of your lines it will never pressurise your system past the level of safety, regardless of what volume it is capable of pumping.
 

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Discussion Starter #6
OK I am trying to find out the rated PSI capacity for the boat. It is not in the owners manual. Also I’ll look at the water heater for it’s capacity. Seems like we would like to go from the 3 gpm to the 5 gmp.
Along these lines the foot pump (Gusher Galley) is 3 gpm foot pump. We would like to put a water filter on it.
Has anyone had any experience with this?
Will it push water through a filter?
If so what filter do you use?

Poopdeckpappy,
When you upgraded to a 5 gpm pump which pump did you get and is it quiet?
Is there any noticeable difference in the noise level of the 3 gpm verses the 5 gpm?
Thanks
Chip
 

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Hydraulics

So if the new pump puts out higher volume but the same pressure, there's no danger. Either the rest of the system can handle the extra volume, or it will choke it back. For instance, if you have a 1.5GPM shower heard--it will only pass 1.5GPM regardless of the pressure. But having a pump with higher volume might allow you to use the shower and galley at the same time without the water dribbling.

To some extent, hose diameters and fittings and the length of the hose runs will all limit the amount of volume the system will handle, and the capacity of your pressure tank will factor in as well. Bottom line is that you may see some improvement in flow, and there should be no risk as long as you're not going from 2.9GPM up to something like, say, 100GPM.<G>
Some pumping theory that might help. If you have a centrifugal pump (it has an impeller that spins) then the pump is capable of pumping a range of water pressure/volume combinations and each pump will usually have a published "pump curve" which illustrates these characteristics for that particular pump.

The piping system that receives the pumped water will increase its resistance as the pump tries to pump more water - this relationship is known as the "system head curve". With the right knowledge you can actually calculate the system head curve for a specific piping system and then plot this on the same graph as the pump head curve. Where the two graphs cross is known as the duty point and this point is the actual performance of that particular centrifugal pump/piping system combination.

On the other hand you could have a "positive displacement" type pump where the internal "slippage" of a centrifugal pump is almost totally eliminated. This type of pump will pump a more or less constant volume of water under most conditions. If the piping system is inadequate to handle this volume of water, then pressures will rapidly rise until you could get pressure induced breaks unless a pressure switch is installed.

Also unless the 1.5gpm shower head is fitted with a sophisticated pressure control system, the volume of water that it passes WILL vary with the pressure.

Lastly the referenced water system has a pressure tank. You will need to check to see how this is plumbed. If all the water from the pump has to pass through this tank, then nothing you do to change pump performance will have any impact on water pressures at the shower as this tank will control all downstream pressures. If the pumped water can reach the shower without going through this tank, then the selected pump will make a difference.

Confused? :D
 

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SDChip, I went from a Jabsco PAR ( very noisey ) to a Shurflo with smart sensor, (very quite), also I went though WM who has a 2yr no question asked return/replace policy, you can actually take the pump back working or not and get a new one, each time extending the policy.
 

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Discussion Starter #10
If we installed the Shurflo 5.7 Extreme 65 psi Variable Speed Pump Controlled by Smart Sensor would you think we coud eliminate the presure tank?
Thanks
Chip
 

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Discussion Starter #11
Just answered my own question:
"Extreme™ Series Smart Sensor Water Pumps
Designed specifically for cruisers, midsize and larger yachts, these pumps incorporate a special sensor that precisely monitors your system’s water pressure and adjusts the motor’s speed, eliminating the need for a pressure switch and accumulator tank"
Chip
 

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If we installed the Shurflo 5.7 Extreme 65 psi Variable Speed Pump Controlled by Smart Sensor would you think we could eliminate the pressure tank?
I am not familiar with that particular pump, but it sounds as if it is regulated by a pressure sensor and will produce up to 65psi of system pressure, which is a healthy pressure for a boat. I design municipal water supply systems where acceptable water pressures normally vary from a low of around 45 psi up to around 100psi.

I strongly suspect that you could install this or almost any other pressure regulated pump and then eliminate the pressure tank..... but why would you want to do this?

Unless you need the space, a pressure tank is a low maintenance fixture that balances out pumping demands. Remember that a dripping tap will very quickly lead to a pressure drop in any small water system not fitted with a pressure tank. Unless everyone on board is a very heavy sleeper, you could then be woken several times in the night by the pump switching on to boost the pressure drop caused by the tap drip! With a pressure tank, even running a tap might not cause the pump to start because this tank is then maintaining system pressures.

If you do decide to remove the pressure tank, please send it my way and I will fit it on my boat! :D
 

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Neil is right, the pressure tank just reduces the number of times the pump runs. It is better for a pump to run longer, with fewer starts. A pressure tank also evens out the difference in pressure you get from the on and off settings. FWIW, I have bought and run at least 100 Shurflo Blaster pumps over the years in street sweeping equipment for dust control. They run all day in the worst conditions you can imagine (thick dust, extreme vibration, heat, dirty water, etc) and frequently run dry for hours (when someone forgets to shut it off). They are extremely reliable and last for several hundred hours of continuous running (which is not recommended by Shurflo). As far as I can tell, the Blaster (which is labelled as a wash down pump) is exactly the same as their water system pump, just cheaper. Cost is not a factor in why we use them, we have used much more expensive pumps but these have really worked well. Obviously I have had them in the boats for years too and have yet to replace one. Not connected to Shurflo, etc, etc., just very impressed with them.
 

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Discussion Starter #14
OK the pressure tank is not a space saving issue, although any added space would be good I guess. I was thinking it was one less thing to manage. I have no idea how long it has been in the boat. We bought the boat a few months ago from the original owner. 1978 Islander Freeport B. Any way he is 89 and does not remember a lot about the boat.
It does seem like a good idea to go ahead and keep it so as the water system runs smoothly.
Although we would want to bypass it for the shower because it will restrict the water flow.
So we will keep it at least for now.
On a side not we checked the hot water heater and it has written on it 127 psi \ 330 psi .

Thanks for the input.

Chip
 

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Good Solution

It does seem like a good idea to go ahead and keep it so as the water system runs smoothly. Although we would want to bypass it for the shower because it will restrict the water flow.
The pressure tank will have an internal membrane that separates the water and air portions of the tank. About the only things that can go wrong are that the membrane can break, which is not a disaster and will not cause a leak but the tank will stop "balancing" or the whole tank could theoretically break or leak - which is a bit more traumatic. Unless you see signs of significant tank corrosion, it will probably work away without any maintenance for many years.

I strongly suspect that the pressure tank is fed from a "T" on the water supply pipe -although it could theoretically be installed "on line". If my suspicions are correct, you will not need to do any piping modifications to obtain the benefit of boosting the shower supply pressure with a more powerful variable speed pump.
 

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Chip,

yes, remove your pressure tank and go for Variable Pump Motor. This was a great improvement to our system (amazingly lower noise and beter shower hot/cold mix as this don't pulse). Although many here stated correctly an upgrade on flow will not damage your system (they are ALL set to around 40psi) I wouldn't upgrade the flow unless you can't find a variable speed pump at 2.8 gpm. First, it will definitely suck more water when doing simple things like washing hands, cleaning and showering (I simply can't fine tune my hands to just open a little when I'm rushing in a sink) and second due to far more DC load posed to your batteries. Stay low, and you'll be happy.
 
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