Pressurized Seawater Supply

[Dockhead]

Most fresh water toilets can run on seawater as well -- if you have a pressurized supply of seawater.

My "other boat" (actually my friend's) has this -- a normal water supply pump which is normally on just like the fresh water pump is, and pipes to all of the three heads on the boat.

Only problem with this is that if any one of those pipes leaks, you can sink the boat, unlike the case with pressurized fresh water.

So what is best practice?

1. Electric solenoid valve which shuts off the through-hull whenever seawater is not actually in demand.

2. Shut off the pump except when seawater is actually in demand. Maybe put the pump on a timer so it shuts off automatically after a couple of minutes? With a switch to shut it on at each appliance?

3. Vented loop(s)?

I'm considering installing pressurized seawater to supply:

1. Two otherwise fresh water toilets
2. Anchor wash
3. Seawater in the galley sink

Four appliances would seem to justify the hassle of installing it, and I will have a free through hull and vented loop after I replace the toilet in the forward heads this year.

[rslifkin]

I'd consider just controlling power to the pump with relays. The pump would be powered by a switch or timer in the galley, or when the windlass control circuit is powered (I like to have that circuit switched to avoid accidental windlass activation), or when a toilet is flushing.

[s/v Jedi]

Best practice is to eliminate the use of seawater as much as possible. In the case of toilets, using seawater comes with many risks and problems that are all eliminated by switching to fresh water so this is a no-brainer.

More difficult for cooling circuits for engines, generators, A/C etc. but options do exist, like keel cooling.

[donradcliffe]

Originally Posted by s/v Jedi

Best practice is to eliminate the use of seawater as much as possible. In the case of toilets, using seawater comes with many risks and problems that are all eliminated by switching to fresh water so this is a no-brainer.

More difficult for cooling circuits for engines, generators, A/C etc. but options do exist, like keel cooling.

So where do you get the 25 gallons per day of fresh water to flush?

[Franziska]

Instead of direct seawater use a saltwater tank which you just fill when you can't flush anymore.

The saltwater flush pump draws from this tank.

[Dockhead]

Originally Posted by donradcliffe

So where do you get the 25 gallons per day of fresh water to flush?

Marine fresh water toilets don't need 25 gallons a day. Mine is 1.5 liters per flush (or 3 for the daily double flush).



I'm into year 2 with the fresh water toilet on my boat and love it. I don't even notice the difference in fresh water consumption.


Query whether it's worth the trouble to supply it with seawater. Maybe not. Certainly not if the system were only for that.

[NorthCoastJoe]

Originally Posted by Franziska

Instead of direct seawater use a saltwater tank which you just fill when you can't flush anymore.

The saltwater flush pump draws from this tank.

I would go this route.

[s/v Jedi]

Originally Posted by donradcliffe

So where do you get the 25 gallons per day of fresh water to flush?

You don’t even notice the water usage of toilets with two people aboard. It is a non issue and I think it’s only 1-2 gallon per person per day.

[Statistical]

Originally Posted by donradcliffe

So where do you get the 25 gallons per day of fresh water to flush?

25 gallons? do you have 18 people on board. Freshwater electric toilets use a lot less water than manual saltwater ones.

[Franziska]

Guys, he mentioned that he also uses it for anchor wash, galley and possibly deck hose down...

[donradcliffe]

Having brought a freshwater flushed boat with 5 aboard across the Atlantic, I have can personally tell you that it is not a non issue. The boat was consuming about 25 gallons of fresh water per day when the water maker went out on day 3. The saltwater fog in the engine room also took out the genset, the inverter, and the bow thruster.

Fortunately I had run the water maker non stop for 24 hours after we left Grand Canaria, so had 400 gallons of fresh in the tanks when it died. I put a 5 gallon bucket of seawater on the floor in each head, and restricted showers.

[Lepke]

I have a large power boat. I have 2 shallow well pumps, one for fresh and one for salt.
The salt water system is mainly to supply the water maker, but also used for washing down the anchor and chain and sometimes the deck.
I have Incinolet toilets, but when I had marine toilets, I used fresh water. It keeps the marine growth and smell down.

[mlydon]

By all means install a wash down pump - feed the galley, too. I’d keep the fresh water heads though. As others have stated, not a lot of water used, much less smell, and if you DO have a problem with your fresh water supply, you can still flush them with salt….

Matt

[Tin Tin]

I think a time relay on the saltwater pressure pump would remove a lot of risk, set it at say 30 seconds. Make sure your bilge pumps can pump faster than the pressure pump.

[Mal Reynolds]

Originally Posted by Dockhead

Most fresh water toilets can run on seawater as well -- if you have a pressurized supply of seawater.

My "other boat" (actually my friend's) has this -- a normal water supply pump which is normally on just like the fresh water pump is, and pipes to all of the three heads on the boat.

Only problem with this is that if any one of those pipes leaks, you can sink the boat, unlike the case with pressurized fresh water.

So what is best practice?

1. Electric solenoid valve which shuts off the through-hull whenever seawater is not actually in demand.

2. Shut off the pump except when seawater is actually in demand. Maybe put the pump on a timer so it shuts off automatically after a couple of minutes? With a switch to shut it on at each appliance?

3. Vented loop(s)?

I'm considering installing pressurized seawater to supply:

1. Two otherwise fresh water toilets
2. Anchor wash
3. Seawater in the galley sink

Four appliances would seem to justify the hassle of installing it, and I will have a free through hull and vented loop after I replace the toilet in the forward heads this year.

I'm a bit puzzled. What problem are you trying to solve here?