What size fresh water pump?

capta · Jun 12, 2015

Bad Obsession said:
Here are my system details:

Compac 23 with a 13.5 gallon fresh water tank.

Outlets are going to be about 10 and 14 feet away from the pump. 1 outlet will be a folding outlet at the slide out sink. The other outlet will be a cold water only cockpit shower in the cockpit.

This means only 1 T in the fresh water line and it will be not too far from where the fresh water hose turns to go out to the folding sink.

What size fresh water pump would you suggest to power these units? 2 or 3 gallon?

I am going to install this system in the fall, I think. I am tired of the pump sink that takes forever to drain the tank when I want it drained and I want a way to have a good shower when I am cruising in the summer. It also makes it easier to wash dished if you have the ability to use both hands and not use one hand to pump the sink. I realize that it is a small water tank and it will drain quickly, but I will keep that in mind when using fresh water. The other thing is that I have plenty of opportunities to fill the tank because I generally use fuel up and refuel every few days.

Thanks for the ideas.

Most marine fresh water pumps are 3.5 gpm or higher. That means if you install an electric fresh water pump, you have less than 4 minutes of water. Instead, I would recommend the Whale foot pumps for the galley and cockpit. They are double action and you aren't going to use half your water turning on and off the taps a couple of times.

Stu Jackson · Jun 12, 2015

Bad O,

You could always add water capacity, but try this:

http://c34.org/bbs/index.php/topic,8217.0.html

I installed it last year, got the idea from Len in Canada, great little thingy.

Get the smallest pump, you don't need the GPM OR the pressure. 2 or even 1.8 will be just fine. Don't bother complicating it with an accumulator and no need for a variable speed gizmo (snake oil for me - I like to hear the pump run!

).

Good luck, sounds like a great idea.

Hope your season is going well (at least better than your last report

).

hewebb · Jun 13, 2015

I installed this one. It supplies water to the head and galley sinks and also to a wash down hose in the cockpit. So far it works quite well. The hose is 3/8" ID, if I remember correctly.

Flojet Quiet Quad II Water Pump (Purchased at RV supply)

This is the faucet I installed in both locations

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Ambassador Marine Aidack Elite Folding Tap with Angled Spout

[FONT=&quot]Purchased from Defender[/FONT]

Bill Roosa · Jun 13, 2015

it is not so much about tank capacity as understanding what flow rate you want for the faucets and shower. The shower is most likely the big user of water. Check the manual for the shower head's flow rate and get the next size up.
If you are concerned about taking too much time to empty the tank during decommisioning consider using a siphon and the bilge pump. Rub Goldburg a fitting from the pump inlet to a clear plastic hose (any hose will work but clear lets you see what is going on with out breaking the siphon). During decommissioning attach your cunningly designed tank drainer to the tank side of the pump inlet and move the other end to the bilge area. Apply a vigrous vacume to the bilge end of the tank drainer using oral pipeation till you get a stream of bubble free water then place the bilge end of the tank drainer into the bilge. Assuming the bilge is below the tank bottom you can just go home and let the bilge pump cycle on and off as the tank drains. easy peasy lemon squeezey

capta · Jun 13, 2015

Bad Obsession said:
Thanks Guys,
I am going to try to head out this Monday and Tuesday for an overnight cruise. The weather is iffy, but I am really wanting to take a cruise and the forecast has already changed from rain to evening thunder storms.

2 gallons per hour will get water back to my shower and give me enough pressure to keep it going? I was going to use one of the cheap cockpit showers like this one: http://www.defender.com/product3.jsp?path=-1|51|2234270|2234272&id=1811179

That is two gallons per MINUTE, not per hour!

Scott T-Bird · Jun 13, 2015

Your water usage shouldn't change all that much by changing from a manual pump to an electric pump. The pump flow rate is one thing ... the faucet flow rate is another. I doubt the flow rate from the faucet will be as high as the pump ... maybe half? You may be able to get specs for the flow rate where the water discharges.

That said, you will waste more water simply because it is easier. The shower will be the largest waste of water, but I don't blame you for the desire!

I doubt you will need or want a pump that is advertised to serve more than one fixture. Why not start out with a cheaper model built just for the galley and see how well it functions? It wouldn't be the end of the world to swap it out at a later date if you find it doesn't deliver.

Jim Seamans · Jun 13, 2015

Hey Matt, If you had been the the Navy - you would know how to take fast showers....

StephenD · May 11, 2023

I have to ask whether my pump is the reason for a lame output from the transom shower. The pump's under the galley sink, has a pressure tank inline, and goes through about 20 ft of pex tubing/flexible hose plus the valve of the shower before reaching the sprayer. There are no flow restriction washers in the new transom shower, at least that I saw.
I think it's a 2.6GPM, 40 psi jabsco pump. It sends water there, but the sprayer has no force. I was wondering if the friction from distance and fittings is killing it. The head sink and shower have strong pressure. I even thought about installing an anchor well washdown, but now I wonder if it would even work without it's own pump.
Do you think I need a higher volume or pressure pump?

Scott T-Bird · May 11, 2023

You should make sure you don't have a kink in the transom shower hose. That's a very common way to lose pressure there. But the pump is pretty small, I think. I've never installed anything less than 4 gpm pump for domestic use. I have bought Shurflo for my boats. So, yes, friction loss and length are also a contributing factor for lack of pressure at the transom, particularly if you include 90 d bends. They are pressure killers.

Don't use a freshwater pump for washdown ... that's a waste of fresh water. The most common practice is to T off a raw water intake with a separate washdown pump. You could use that 2.6 gpm pump that you are using for domestic water now.