Location of watermaker discharge

[mlibkind]

I will probably purchase a Spectra Ventura 150 watermaker for cruising, but am still working with the company to get an acceptable answer to one question. Maybe one of you has dealt with this and can lend some insight.

The Ventura 150 manual states, “The brine discharge thru -hull should be mounted above the waterline, in or just above the boot stripe to minimize water lift.”

My thinking is that this would put the discharge under water whenever sailing on or above a close reach in moderate winds and maybe even on a broad reach given that the boot stripe is only several inches high and cruising boats tend to be fairly heavily loaded. This could put the discharge underwater a good deal of the time. But Spectra says, “IT CAN GO UNDER WHILE HEALED OVER. IT JUST SHOULDN’T STAY UNDER.”

The purpose of keeping it low is to minimize water lift. But if another 6 to 12 inches makes a difference, then it seems like they are operating on the ragged edge of the feed water pump. But the feed water pump is operating at something like 150 psi and 1 foot of water is about 0.5 psi.

Any thoughts on where one should install the discharge?

[Lojanica]

Originally Posted by mlibkind

I will probably purchase a Spectra Ventura 150 watermaker for cruising, but am still working with the company to get an acceptable answer to one question. Maybe one of you has dealt with this and can lend some insight.

The Ventura 150 manual states, “The brine discharge thru -hull should be mounted above the waterline, in or just above the boot stripe to minimize water lift.”

My thinking is that this would put the discharge under water whenever sailing on or above a close reach in moderate winds and maybe even on a broad reach given that the boot stripe is only several inches high and cruising boats tend to be fairly heavily loaded. This could put the discharge underwater a good deal of the time. But Spectra says, “IT CAN GO UNDER WHILE HEALED OVER. IT JUST SHOULDN’T STAY UNDER.”

The purpose of keeping it low is to minimize water lift. But if another 6 to 12 inches makes a difference, then it seems like they are operating on the ragged edge of the feed water pump. But the feed water pump is operating at something like 150 psi and 1 foot of water is about 0.5 psi.

Any thoughts on where one should install the discharge?

The nice thing about 12" above waterline is it keeps both the land based and waterbased pests from taking root.

[neptunesjester]

Interesting. Do they mention anything about where to mount the pump in relation to the discharge? Would seem to me that you could locate the pump anywhere above or below the bootstripe which, without guidance on how much head the pump can handle, makes the recommendation nonsense.

You can build a RO unit for a fraction of the cost. Schedule 80 pvc is more than adequate for the pressure vessel. A plumbing supply house should be able to set you up with higher schedules if it makes you more comfortable. The membranes can be sourced, and all you need is some pvc, a 1.5 hp ac piston pump, and some hydraulic hoses, and a day to assemble and install, and you'll produce fresh water.

[Moody46CC]

I had a Spectra Catalina 300 in a former boat. Units was under the port settee, probably just below the waterline. The discharge outlet was just behind the unit and located 6" above the boot line. Never had a lick of difficulty. I tended to run the unit when under power as opposed to sailing, simply to keep battery discharge to a minimum.

I prefer discharge outlets above the waterline whenever possible. Have a thing about keeping the number of holes below the water line to an absolute minimum.

[Lojanica]

I put a bronze 2 way ball valve in the line so I could use the above the waterline through hull for both a deck cockpit drain and the waste water maker discharge.

[colemj]

Originally Posted by neptunesjester

Schedule 80 pvc is more than adequate for the pressure vessel.

You are kidding, right? 2.5" schedule 80 pvc has a maximum pressure rating around 400psi at 70*F. At the temperatures many run at, the max pressure is around 300psi.

Watermakers run at 800-900psi.

Then there is the problem of ID - which is neither very accurate nor very consistent across any piece of pvc pipe. Getting a high pressure seal with the membrane would be a nightmare.

Not to mention the problems with PVC endcaps and appropriate connections to them.

This is terribly bad advice.

Mark

[Spectra]

Michael in Tech Support at Spectra responds;

The main reason we want the brine discharge above the water line is so you will know when the watermaker is running. This is also a good troubleshooting tool letting you know the system is moving water through it.

A few extra feet of head pressure on the brine discharge will not effect the performance of the system. The best source of information for Spectra Watermakers is from techsupport@spectrawatermakers.com

[mlibkind]

Originally Posted by Lojanica

The nice thing about 12" above waterline is it keeps both the land based and waterbased pests from taking root.

That's a good point. I know that barnacles, etc. often take hold in thru-hulls and one less to worry about is good.

[mlibkind]

Originally Posted by neptunesjester

Interesting. Do they mention anything about where to mount the pump in relation to the discharge? Would seem to me that you could locate the pump anywhere above or below the bootstripe which, without guidance on how much head the pump can handle, makes the recommendation nonsense.

You can build a RO unit for a fraction of the cost. Schedule 80 pvc is more than adequate for the pressure vessel. A plumbing supply house should be able to set you up with higher schedules if it makes you more comfortable. The membranes can be sourced, and all you need is some pvc, a 1.5 hp ac piston pump, and some hydraulic hoses, and a day to assemble and install, and you'll produce fresh water.

They want the feed water pump below the waterline so that there is always a positive pressure. I know with some RO systems, e.g. the AC system that is sold by a company in San Diego, have both a primary pump and a high pressure pump. The primary pump allows one to place the system anywhere.

I don't find this requirement too objectionable, but it would be better not to have it.

Yes, I know that I can build one for much less or even buy one for less, but then it will be an AC motor (yes, the San Diego company has a DC version). A friend bought one of the AC versions from the San Diego company but he has a genset.

Either way, these are very energy intensive systems because at least 90% of the high pressure water just runs out the discharge. The Spectra recovers much of the energy in the discharge. The net result is about 6 gph at 10 amps. I will have enough energy to run this the necessary 2 hours per day (averaged) to meet more than our water needs. Two hours is 12 gallons minus 2 gallons for flush. That's 10 gallon for four people which allows for shower! But in reality one runs it more like every other day or every third day because this reduces flush water on a per day basis. My final comment is that when possible I would buy water (in the Caribbean it is not free) because it is cheaper than making it.

Thank you for the great thoughts.

[mlibkind]

Originally Posted by Moody46CC

I had a Spectra Catalina 300 in a former boat. Units was under the port settee, probably just below the waterline. The discharge outlet was just behind the unit and located 6" above the boot line. Never had a lick of difficulty. I tended to run the unit when under power as opposed to sailing, simply to keep battery discharge to a minimum.

I prefer discharge outlets above the waterline whenever possible. Have a thing about keeping the number of holes below the water line to an absolute minimum.

Good to hear from someone who owned a Spectra. I would love to know how loud it sounded when operating. They quote sound levels, but I really can't imagine what it is like.

[mlibkind]

Originally Posted by Lojanica

I put a bronze 2 way ball valve in the line so I could use the above the waterline through hull for both a deck cockpit drain and the waste water maker discharge.

Just a thought. Many older boats have small cockpit drain(s). For most uses, e.g. rain, this works fine and that is about the worse condition that you have to consider. But cruisers might want to consider what will happen if a wave enters the cockpit. The thru-hull for the watermaker will not add very much capacity but it is better than not having it.

You might think this is very unlikely, but it has happened to me in the Sea of Cortez and I've crossed the Gulf Stream when it could have easily happened.

[mlibkind]

Originally Posted by Spectra

Michael in Tech Support at Spectra responds;

The main reason we want the brine discharge above the water line is so you will know when the watermaker is running. This is also a good troubleshooting tool letting you know the system is moving water through it.

A few extra feet of head pressure on the brine discharge will not effect the performance of the system. The best source of information for Spectra Watermakers is from techsupport@spectrawatermakers.com

Thanks for the expert advice. I thought what you say should be the case, but when I wrote Spectra they did not say anything at all like that. They simply stated that they wanted it above the water line but as low as possible. I'll put it 12 inches about the boot stripe. If heeling any more than that then I'm not going below and fiddling with turning on the watermaker.

[rebel heart]

I have a low output 40e.

I routed the brine discharge to a faucet in the head's sink. Initially I did it because I was lazy. But it's actually been pretty interesting because you see when there's air in the line, as the brine discharge is sort of white with a lot of bubbles in it.

I've been having some issues keeping the air out of my intake so it's been a helpful way of seeing whether I scooped up any air.

[Moody46CC]

Originally Posted by mlibkind

Good to hear from someone who owned a Spectra. I would love to know how loud it sounded when operating. They quote sound levels, but I really can't imagine what it is like.

The machine was very quiet. Sitting in the salon w/o the main engine running, a Yanmar 4JH3, there was a slight hum that could not heard in the cockpit. When the main engine was running, you really could hardly or not at all hear the Spectra.

[mlibkind]

Originally Posted by Moody46CC

The machine was very quiet. Sitting in the salon w/o the main engine running, a Yanmar 4JH3, there was a slight hum that could not heard in the cockpit. When the main engine was running, you really could hardly or not at all hear the Spectra.

This is fantastic news. And I must add that you guys out there have been fantastic with supplying info. Thank you.