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Old 07-01-2019, 05:30   #1
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Spectra watermaker knock/ pulsation

I just got my 10% Clark pump DIY watermaker going. Using a Spectra pump bought alone several years back.

Anyway, setup with 21" membrane and custom hoses, seems to be making water ok. Have only flushed the chemicals from membrane and run about another 20 minutes so far.

About every 5 seconds, the pressure goes from about 70psi up to about 90psi and then makes a pretty gentle knocking noise and also brine pulsates slightly as does product water. Then goes back to 70 and quick Spike to 90, slight knock, repeat, etc.

Is this normal? Will increasing the pressure in accumulator bladder help this?

It really isn't alarming and maybe be perfectly normal.

Currently in Lake Boca Raton
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Old 07-01-2019, 05:52   #2
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Re: Spectra watermaker knock/ pulsation

Yes, the sound is normal.
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Old 07-01-2019, 06:00   #3
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Re: Spectra watermaker knock/ pulsation

Ken,

I've only been aboard one other boat with one running. But seemed about right.

Thanks!

Does fiddling with the accumulator pressure make any difference? Do you need to check that pressure on the bladder often?
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Old 07-01-2019, 06:09   #4
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Re: Spectra watermaker knock/ pulsation

No, you wonít need to check it or fuss with it after itís set.
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Old 07-01-2019, 08:52   #5
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Re: Spectra watermaker knock/ pulsation

When mine knocks it usually means the high pressure pump is not getting enough water. I clean the raw water strainer and/or pre-filter and that resolves the problem.

Your system should be running at a consistent 900 psi.

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Old 07-01-2019, 09:54   #6
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Re: Spectra watermaker knock/ pulsation

This is normal operation. Feed water pressure will pulse from about 70psi to between 80-90 psi. The knock you hear is the normal shuttling of the pump internal components. To understand how the Clark Pump functions, I recommen going to the Support menu on the Katadyne/Spectra website and look for the animation they offer on pump operation. Ciao.
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Old 07-01-2019, 09:57   #7
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Re: Spectra watermaker knock/ pulsation

Regarding the operating PSI, it depends on salinity and temperature of the feed water.
Higher with lower temp and higher salinity, lower with the reverse.
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Old 07-01-2019, 10:22   #8
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Re: Spectra watermaker knock/ pulsation

has anyone added a high-pressure gauge into a 150/200 Spectra? might be interesting, and useful.
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Old 07-01-2019, 10:48   #9
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Re: Spectra watermaker knock/ pulsation

Thanks for responses. Making water now under sail to Miami.

On the subject of useage cycles.

Spectra rowboat 150 manual suggests a fresh flush after every use and only running every several days.

On my previous small output Katadyn I ran every few days or pickled as 1 quart I think was enough biocide for 6 months storage.

So on this is 5 days all you get in wintertime tropical service on a flush? How many days can you realistically go without running or flushing.

And can you get a few weeks on a flush vs. just the 5 days? For example if I spent 2-3 weeks in Georgetown will not plan to use watermaker at all. Guess I could flush it once a week with the Exuma market RO water?

Cheers,
Jeff
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Old 07-01-2019, 11:34   #10
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Re: Spectra watermaker knock/ pulsation

Without flushing our system, we run it every day or maybe go every other day without a problem. Or we can go 5 days after a fresh water flush. Don’t worry about having to use it in a harbor for a half hour or so just to use it, nothing bad will happen to the membrane, but you might plug up the pre-filters a little prematurely. No matter though, because you can clean them and re-use the prefilters 3-4 times.
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Old 07-01-2019, 14:14   #11
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Re: Spectra watermaker knock/ pulsation

How often you need to flush or run depends on whats in tbe water that you are in. Rich river water might just make it 2 or 3 days, clear reef water might make a week.
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Old 08-01-2019, 04:32   #12
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Re: Spectra watermaker knock/ pulsation

Quote:
Originally Posted by Kenomac View Post
Yes, the sound is normal.
+1 Normal for a Clark Pump.
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Old 09-01-2019, 05:12   #13
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Re: Spectra watermaker knock/ pulsation

Quote:
Originally Posted by briblack View Post
has anyone added a high-pressure gauge into a 150/200 Spectra? might be interesting, and useful.



There should already be a pressure gauge on these units. If not the pressure gauge (liquid filled 0-200psi) should be installed between the feed pump and the Clark pump. Adding a high pressure gauge to the high pressure side of the system won't tell you as much trouble shooting wise as the lower pressure gauge will.
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Old 09-01-2019, 06:28   #14
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Re: Spectra watermaker knock/ pulsation

We ran a 150 during two years of cruising. With 66 gallons of tankage, here is what we did.

1. Ran for X hours day 1. Shut unit down.
2. On the Following day, Ran again until full, and then did a freshwater flush.
Good for 7 days before either doing another flush or repeating steps 1&2.

Chris
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