Flushing AC line

[mawyatt]

Don't your guys have seacocks on your A/C discharge lines? The 450DA's do.....to flush one but not both units, you just close a valve.

I use Gary's bucket method, but the timing is different. I use 40% phosphoric acid mixed with equal parts of water then run it thru with the A/C pump. When the bucket is empty, I shut down the A/C's, wait 3-4 minutes and turn 'em on and let them run the rest of the day.

Frank,

If I understand you don't circulate the mixture. Close inlet then suck it in until bucket is empty and shut pump down and let it sit. Then open inlet, turn pump on and pump it out and let AC run as normal.

 

[Four Suns]

If that acid hits your bottom paint by letting it go out the side through hull, it'll destroy the bottom paint in that area... turns it green... just an FYI.

 

[At Ease]

The chlorine tabs are the same as the pool store sells. I prefer the 1 inch ones. The only issue is you will eventually eat a hole in your strainer basket. I usually put them in when we are at peak usage on the air units as to not let them sit.

Jack

:thumbsup: Thanks!

 

[Alex F]

Can you guys explain what's wrong with just dropping the chlorine tab in the seastrainer basket and have the A/C running in regular mode using sea water intake (I assume the tab will slowly disolve within a short time frame while cleaning the system)?

 

[osd9]

Alex...that would probably work too.....but I like to know it all worked and went through the system in a few short hours....then done for the season......no guess work.

 

[Alex F]

Dom,

How often do you do this flushing procedure, just once as part of the spring recomissioning or do you also do it few times during the season, as some other folks do?

I understand that the flushing is done as part of preventive measures for clugging, so if the flow is fine what's the banch mark to determine the need for the flushing?

BTW, while my boat is on hard during the winter the lines are filled with antifreeze.

 

[osd9]

I personally do it once a season....usually around July/August timeframe....when the critters start to grow more frequently....I use the growth on my props as the barometer for 'when'....

 

[fwebster]

Alex........

You are talking about 2 things and processes: Flushing is cleaning the accumulated marine growth and silt out of the cooling coil lines. The chlorine treatment is a preventitive measure to keep the growth from occurring.

You cannot leave the chlorine tablet in the strainer basket with the system in normal operating mode because the basket has plastic parts that the chlorine will attack and dissolve. Re-read Dom's post......put the chlorine in and immediately begin constant water flow. Dom uses "city" water, and that works even with the A/C system off because the pump is a magnetic impeller pump and the city water bypasses the impeller and flows thru the coils. But, turning the A/C system on the boat to its lowest setting also causes the system to run almost constantly and also works. If the water flow stops, like when the A/C regularly cycles off and on, in about 30 minutes the strainer contains a chlorine solution stronger than bleach. For those who use chlorine and think you are immune from the basket being destroyed, it happens, but in some cases it takes a year or more........spend the $50 and get an extra strainer basket 'cause you are gonna need it sooner or later.

The chlorine tablets will kill and prevent marine growth while it is in the system, but it will not remove accumulated growth, whether it is dead or alive. You must use acid, Rhydlime (?) etc. to clean the lines. You know you need to clean the system when the water flow out of the A/C discharge is noticably reduced.

 

[tobnpr]

Unless your boat is wet-slipped, and the A/C is run constantly, or at least very frequently (as in a dehumidification mode), "flushing" with acid or Rydlyme is not necessary for removal of marine growth- there won't be any. If you run your A/C only when using the boat for a day or two at a time, a few times a month, it's a non-issue.

There needs to be raw water flow on a frequent basis to introduce- and then sustain- marine growth. Stagnant seawater lying in the lines will not allow growth to occur.

 

[flarepoman]

I had a high pressure shutdown problem.

I just went through this last week. I took the intake hose that comes into the A/C unit off, I had some spare 5/8's hose hanging around and stuck a funnel in one end and put the other on the inlet of my A/C.
I blew it out to get the water out and then held the hose way up in the air and filled it with bleach untill it stopped.

Let it sit for 1/2 hr and reinstalled the water hose from the pump turned on the A/C and It worked fine.
I think I may have to flush the whole system in the fall. I got some good ideas from this post.

 

[trit21]

Instead of using chlorine tablets how about bromine tablets. They are used in hot tubs and are supposed to be easier on parts of a confined hot tub. Not really sure of the chemical difference but I know bromine does not have that chlorine smell like a chlorine tablet would.

 

[fwebster]

I believe the need to flush your system is location dependent. We are in NW Fla in warm salt water 12 months a year. My boat a/c system will pick up enough growth to need annual flushing and I do use only the dehumidification mode most of the time instead of the cooling. If you live in the North and haul out every year, you might not get as much crud in your system as we do down here.

 

[trit21]

Right now we are having to flush almost once a month for some reason. AC systems are getting clogged with all kind of crap and the zebra mussels (I think that is what they are) are working their way through the strainers and making home in the cooling lines. For some reason it just got real bad about 2-3 weeks ago. Wasn't like this last year and thoughts are the construction in the area, about 3-4 blocks away, may be affecting this with run off into the basin.

 

[Alex F]

Alex........

You are talking about 2 things and processes: Flushing is cleaning the accumulated marine growth and silt out of the cooling coil lines. The chlorine treatment is a preventitive measure to keep the growth from occurring.

You cannot leave the chlorine tablet in the strainer basket with the system in normal operating mode because the basket has plastic parts that the chlorine will attack and dissolve. Re-read Dom's post......put the chlorine in and immediately begin constant water flow. Dom uses "city" water, and that works even with the A/C system off because the pump is a magnetic impeller pump and the city water bypasses the impeller and flows thru the coils. But, turning the A/C system on the boat to its lowest setting also causes the system to run almost constantly and also works. If the water flow stops, like when the A/C regularly cycles off and on, in about 30 minutes the strainer contains a chlorine solution stronger than bleach. For those who use chlorine and think you are immune from the basket being destroyed, it happens, but in some cases it takes a year or more........spend the $50 and get an extra strainer basket 'cause you are gonna need it sooner or later.

The chlorine tablets will kill and prevent marine growth while it is in the system, but it will not remove accumulated growth, whether it is dead or alive. You must use acid, Rhydlime (?) etc. to clean the lines. You know you need to clean the system when the water flow out of the A/C discharge is noticably reduced.

Frank,

This makes perfect sense to me, but I still have a question on the following:

.....Dom uses "city" water, and that works even with the A/C system off because the pump is a magnetic impeller pump and the city water bypasses the impeller and flows thru the coils. But, turning the A/C system on the boat to its lowest setting also causes the system to run almost constantly and also works. If the water flow stops, like when the A/C regularly cycles off and on, in about 30 minutes the strainer contains a chlorine solution stronger than bleach....

When Dom's city water runs thru, does it mean that it creates enough pressure to have the solution circulate trhough the system and come out from the a/c line thru hull fitting? When I winterize my a/c unit I have to use priming pump connecting to the line (i connect it to the hose right after the seastrainer). So, with the pump ON I don't get anything going trough the system and nothing comes out on the other end until I turn the a/c unit on, then it only takes about 30 seconds to see the pink coming out of the fitting. So, what I'm trying to understand is, does it mean that city water has much more preasure over the priming pump to allow the solution to run all the way thru the system and gome ot on the other end?

I personally do it once a season....usually around July/August timeframe....when the critters start to grow more frequently....I use the growth on my props as the barometer for 'when'....

Dom,
It sounds like a mid season routine, I guess it goes along with mid season bottom cleaning some people do. I think my situation is a little different due to the fact that your boat is in water all the time and I'm in only for about 5 months, but I think it's still only a matter of time until I have to address the issue, unless I use the chlorine tabs enough to prevent the growth.

 

[fwebster]

Alex,

Since I don't know what your priming pump is, I can't give you an answer, however, the "city" water supply has more volume and pressure than the A/C circulation pump on your boat. In fact, I use a city water connection to my A/C strainer many days when I"m working around the boat but not leaving the slip. City water is chlorinated and has enough pressure to help keep the system clean.

 

[mawyatt]

I believe the need to flush your system is location dependent. We are in NW Fla in warm salt water 12 months a year. My boat a/c system will pick up enough growth to need annual flushing and I do use only the dehumidification mode most of the time instead of the cooling. If you live in the North and haul out every year, you might not get as much crud in your system as we do down here.

Frank,

We have been lucky, 3 years this coming March in salt water here in Clearwater. I have not flushed the AC system yet and it still flows OK, but realize I need too. After reading this thread I think I'll use your approach. Do you just allow the solution to flow overboard after sitting awhile? I noted Gary's comment about the bottom paint and will keep a water flow around the AC outlet. One of my dockmates uses the bromide tablets to keep the growth down, is this safe for the system and worthwhile?

 

[fwebster]

Mike,

One of the reasons I use phosphoric acid is because you can buy a mild solution at Home Depot for $13/gal then cut it further with equal parts of water. You can run it thru the system and it will not discolor the bottom paint and the acid solution is so weak it isn't an environmental concern.

Look for a product in the paint department called "Phosphoric Prep & Etch" by Kleen-Strip. It is in gallons and is light green in color.

I do use chlorine in the hot part of the summer when the system is running most of the time. Chlorine will eventually eat up the plastic bottom in the strainer basket; I don't know about bromide tablets.

I've ended up with an inexpensive system that adds very little time to my regular maintenance requirements. Acid flushing once in the Fall and an occasional chlorine tablet in July-Sept keeps our system in good shape. I've only had 2 strainer baskets sine 1997 when we bought this boat.

Adding chlorine or bromide isn't going to clean much out of a clogged up system, but will slow down the growth. If your system shows a decreased water discharge, then rig up a bucket and go to Home Depot!

 

[mawyatt]

Frank,

Thanks for the reply. Think I'll follow your advice and head to Home Depot this weekend.

 

[SCORPIO]

Would CLR work to remove the buildup?

 

[mawyatt]

Picked up the phosphoric acid at Home Depot and flushed AC per Frank's recommendations. No stain on hull or discoloration of bottom paint. Also picked up a copper coupling that I put in the strainer, so we'll see if it helps keep the marine growth down.

Thanks for the help Frank,