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Old 26-04-2015, 11:49   #1
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Spectra Watermaker flow rate question

Hi all,

I just installed a Spectra Ventura 150 manual watermaker. I have a question since I have never seen another unit in operation. Should the product water flow drop to zero on every piston stroke?

Pressure seems good at about 60psi, climbing to about 70psi on each stroke. Flow gauge shows over 6gpm, but drops for a second to zero with every stroke of the high pressure pump. The sample water faucet completely stops for about a second each stroke. I've run the unit about 12 hours now to completely get rid of the membrane preservative, but I don't think that the flow dropped so dramatically each stroke during the first hour or two.

I'm in unfamiliar territory here (as usual).

Thanks,
Gary
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Old 26-04-2015, 14:53   #2
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Re: Spectra Watermaker flow rate question

Do you have an accumulator tank in the unit?
It would be quite small, about 3 or 4 inches in diameter and about 6 inches long, with a Schrader valve on the end.
It needs to be pumped up with air, about 60 psi if I remember correctly.
It prevents the feed pump from momentarily shutting off during the spool valve shunting.
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Old 26-04-2015, 15:50   #3
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Re: Spectra Watermaker flow rate question

Hi,
On my Spectra (a Cape Horn Extreme), the fresh water output momentarily stops flowing with every piston stroke. It's very quick -- the flow rate gauge dips to down (zero?) and then pops right back up. It's definitely not stopped for 1 second, maybe 1/10th a second?

I had one of the first Spectra's on my previous boat, and it did the same thing.

Good luck!

PS-- Both of our accumulator tanks arrived already pressurized. We didn't have to pump them up. Our feed pressure gauge also varies over the stroke, I can't remember how much, but 10 psi sounds about right.

PPS-- Now that I think about it, our first Spectra was lower output (5-7 gph?), and it would take about a second for the output to 'climb' back up to the peak rate after each stroke. But it never hung out at 0 for more than a moment.
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Old 26-04-2015, 16:51   #4
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Re: Spectra Watermaker flow rate question

Yes, I've got an accumulator. It was pre-charged by Spectra (I want to say 85PSI but I'm not looking at it right now). Maybe I'm overstating the "one second" but the flow is definitely stopping then restarting.

I'm very new to watermakers. Perhaps I should have seen one in operation before I tackled the install!
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Old 26-04-2015, 22:08   #5
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Re: Spectra Watermaker flow rate question

Come to think of it, the accumulator keeps the feed pump from momentarily stopping during the spool valve shift.
Our production gauge ball drops to zero with each shift but goes back up to normal within a half second or so.

Spectra 180, 15 years old, original membrane, but Clark pump factory updated a few years ago.
Running on LiFePo4 batteries 8 amps at 13.2 volts with engine off, solar only and we get about 8 gallons an hour at about 100 ppm or less.
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Old 27-04-2015, 00:31   #6
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Re: Spectra Watermaker flow rate question

Its normal and expected for the flow meter to drop to zero between strokes of the Clark pump,

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Old 27-04-2015, 02:56   #7
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Re: Spectra Watermaker flow rate question

Our Spectra Ventura 150 has only just been unpickled so we do not have much experience with it yet. However, what I did notice that we had a low pressure showing and there was a large drop on each stroke. As others have stated, the accumulator tank needs to be pressurised to 65 psi. When I checked ours it was less than 15 psi. I have now pumped up but have not been able to test due to the huge storms we had in Sydney last week which have made the water in our mooring bay filthy.

The output when I did run was about 25 litres per hour, that is, 6.5 US gallons per hour. The stated production rate is 150 US gallons per day, that is 6.25 US gallons per hour or 23.7 litres per hour. Therefore we were getting slightly higher than this.
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Old 27-04-2015, 10:06   #8
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Re: Spectra Watermaker flow rate question

FWIW, it IS permissible to call the technicians at Spectra, who are very knowledgeable and very helpful. Might be quicker than getting all of our opinions....I am a Spectra user, too, and have been for eleven years.
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Old 27-04-2015, 15:41   #9
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Re: Spectra Watermaker flow rate question

Thanks all! I appreciate hearing about the experiences of actual users. With regards to calling Spectra, I am thrilled to hear that they are responsive. Unfortunately, I guess I've gotten used to the typical lack of customer support for most products.
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Old 28-04-2015, 07:51   #10
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Re: Spectra Watermaker flow rate question

Quote:
Originally Posted by Gary H View Post
Thanks all! I appreciate hearing about the experiences of actual users. With regards to calling Spectra, I am thrilled to hear that they are responsive. Unfortunately, I guess I've gotten used to the typical lack of customer support for most products.
You can always contact me directly with any Spectra issue as well. I've been doing this for years here on Cruisers Forum.

Though Spectra will gladly answer your call and help you through any questions they are usually taking care of multiple things at once so we try to take some of the load and pressure off of them.
But what you are experiencing is perfectly normal. Your Clark pump has two cylinders which create the needed pressures within the membrane vessel. But only one cylinder at a time creates the pressure and each shift alternates the cylinder used to create that pressure. This is why you are seeing the instant drop off of both the product flow and on your pressure gauge. You will also notice the same effect on your brine discharge overboard.
The accumulator tank on your system should be factory charged to 60psi. These rarely if ever need to be adjusted. It's sole purpose is to soften the plumbing hammer effect created when the Clark pump shifts.
Your pressures of 60-70psi are perfect for a VT150 and your flow meter showing 6+gph indicates all is well within your system. Again anyone is always welcome to either ask here or call me or Dulcesuenos anytime you have a question on your Spectra watermakers.

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Old 28-04-2015, 07:57   #11
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Re: Spectra Watermaker flow rate question

Quote:
Originally Posted by clownfishsydney View Post
Our Spectra Ventura 150 has only just been unpickled so we do not have much experience with it yet. However, what I did notice that we had a low pressure showing and there was a large drop on each stroke. As others have stated, the accumulator tank needs to be pressurised to 65 psi. When I checked ours it was less than 15 psi. I have now pumped up but have not been able to test due to the huge storms we had in Sydney last week which have made the water in our mooring bay filthy.

The output when I did run was about 25 litres per hour, that is, 6.5 US gallons per hour. The stated production rate is 150 US gallons per day, that is 6.25 US gallons per hour or 23.7 litres per hour. Therefore we were getting slightly higher than this.

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Just a quick response. If your accumulator tank was only pressurized to 15psi and has not been tampered with or adjusted by someone then I would keep a close eye on it. The factory pressure is 60psi. Your accumulator tank may be failing, which is rare, if it can not hold this pressure. At 15psi you should be experiencing what seems to be hard shifts in your Clark pump. Your manual will tell you that you can adjust the pressure in the accumulator tank to make the Clark pump shift as smooth as possible. Because of the inherent design of all membranes not being equal you could play around a bit with the pressures but setting it at 60psi and forgetting it is usually the best thing to do as this seems to be the sweet spot for theses systems.
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