• Mobile App For Android Now Online!

    Download it here. The app is searchable in the Google Play Store under Sailboat Owners.

    Sorry iPhone/iPad users, we are still waiting on Apple. :(

    Click the X in the upper right corner to make this go away

Water Distribution on Catalina 320

Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
I am disappointed with water pressure in the water system. It seems very weak. I'm convinced that the pipe diameters from the two tanks are too small and the 90 degree fittings make it worse. My experience on my previous boat is that the problem originates when the pump can't draw enough water and the supply side is the most important place to improve. I want to replace the 15 mm PEX supply lines and put in 3/4" and eliminate fittings (there seems to be an abundance of fittings where the 2 lines converge, with valves, just before feeding the pump. Has anybody had he same experience? Is the weak pressure built in on purpose as a water-saving device. To me, it's just frustrating. It seems that feeding new water distribution lines from the tanks to the pump is going to be a monumental task, if not impossible.
 
Jan 4, 2006
3,820
Hunter 310 West Vancouver, B.C.
Very doubtful it's the sizing of your lines as they sound plenty big enough for your flows. I'm betting it's your pump pressure setting that's too low.

Try installing a pressure gauge as far as you can from the outlet side of your distribution pump to see what pressure you've got with all of your outlets closed. Should be around 30 PSI for decent flow from your outlets. Open one outlet a small amount and see what the pressure does.

NOTE: this is only the beginning, only the beginning folks :dancing: ! At this point, we're only testing for pump performance. To check for line loss (as you suspect), we'll need to install a few more pressure gauges. It sure beats the hell out of pulling new lines. For now, I'm still betting it's your pump pressure setting that's too low.

Let us know what happens.
 
  • Like
Likes: Allan12210
Jan 22, 2008
1,587
Hunter 34 Alameda CA
Is it the pressure or the flow you are disappointed in? All of the things like tubing diameter and fittings can reduce flow. Check the filter right after the pump and see if the aerators at each faucet have crud in them.
 
Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
To be sure, I'm not sure about the pump, either. The pump is an older Shurflo 4.0 GPM and I don't have any idea if there is even a way to adjust pressure setting. I'm guessing there is not. I had a new Shurflo Aqua King on my previous boat and it would not deliver water when I supplied the pump from the tank with 1/2" PEX. I changed the supply side to 3/4" flexible hose without fittings and the pressure was good. That's why I think this is a supply side problem. The tanks are virtually as low as the pump, the pipe diameter has too much skin friction, and all of the fittings lead to flow losses. Quite simply the pump is starved for water and the downstream pressure is low. By reducing flow losses on the suction side, the pressurized side should be fine and that is what I am thinking is the problem now. If I thought I could correct it simply by changing the pump, I would do it in a minute, but I suspect that the supply side can't deliver the water to feed the pump. In particular, the bow tank is very far away from the pump in the stern. The pressure when feeding water from the bow tank IS less than when feeding water from the stern tank, but both are unsatisfactory.

I'm not finding a pressure gauge that is made for 15 mm line size - the size Catalina put on the boat. There seems to be some cheap ones that fit a garden hose connection. I suppose I would need to cut the lines somewhere to put a tee on a line with a garden hose adapter. I don't really want to buy an expensive gauge just to verify that my assumptions are correct! :huh:
 
Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
I've removed and cleaned all the filters. Crud in the tanks was definitely causing pressure problems to the point that water flow just about stopped. It is a problem but it's not like it is a problem that I haven't considered.
 
Feb 26, 2004
21,898
Catalina 34 224 Maple Bay, BC, Canada
Scott, you're looking in the wrong direction, buddy. My 34 foot boat has 1/2" hose for all its domestic water and I've never had a problem in my 23 years of ownership of a 1986 boat.

You should begin to develop a systematic approach to the issue, many of which are included in the comments already. They are: pump pressure, filter cleanliness, clogs in lines, aerators, etc.

We're actually trying to save you money. Changing to 3/4" hose will be a waste of YOUR money.
 
Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
The faucets deliver water, it is just annoyingly weak. I'm left wondering if it is on purpose as a water-saving measure, or is the pressure supposed to be stronger? I know that the pressurized side of the system is fine. It's either the supply side with low delivery or the pump. I think I will run a test with the pump using a temporary setup to deliver water to the pump more efficiently. I've already removed the pump. I can do a bench test on the pump at home.
 
Jan 4, 2006
3,820
Hunter 310 West Vancouver, B.C.
I know that the pressurized side of the system is fine. It's either the supply side with low delivery or the pump.
You can't possibly make the above statement without the use of pressure gauges. Is the suction side low or even negative ? ? ? ? ? You can't possible know without numbers.

Trust Stu, trust Allan, trust me, there is nothing wrong with your suction and distribution lines unless there's a dead rat or two stuck in there. Your problem lies elsewhere.


You should begin to develop a systematic approach to the issue, many of which are included in the comments already. They are: pump pressure, filter cleanliness, clogs in lines, aerators, etc.
Do exactly what the man says. Have another coffee and think about this whole problem as a system starting with the tank and ending at the tip of the faucet. Draw a sketch and write down your results. And numbers, numbers, numbers are going to save you.

As for the cost of gauges, think cheap. Under $10.00 ea. You're not after accuracy, only close. Install the "T" 's in an inconspicuous place and pull them out later and install fitting plugs. Cheap gauges have a habit of leaking after a few years.
 
Last edited:
Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
Well, I can tell just from visual observation that the water delivery side of the system is a poor, inadequate design. The pressurized side is fine. I have visual access to all of the pressurized lines. The line sizes are suitable and I've inspected and cleaned all of the filters. There are no defects in the pressurized distribution system that would cause a pressure inadequacy at the faucets and I haven't found any problems with the faucets themselves.

You are right. I should start at the tank and work my way forward. However, your anecdotal testimony is that the delivery side is adequate and I'll take that into consideration, despite my suspicion that it is not. Perhaps it is a subjective matter. I may have an expectation that the pressure should be stronger than I found it to be last season. Perhaps it is what it is and I shouldn't expect better. I'm not saying that there isn't any water delivery. I'm just saying that I think the pressure is not what I want.

But I think I will start with a bench test on the pump because I am also not confident with the pump. Believe me, I am not enthusiastic about changing out the supply lines even if I think I can do better. The runs seem almost impossible to make without major surgery! That's pretty much why I asked the question.
 
Jan 4, 2006
3,820
Hunter 310 West Vancouver, B.C.
1617043472021.png


Perfect. Reasonable accuracy. I've used these before in the field as a throw away when they're covered in oil.

Amazon.
 
Jan 22, 2008
1,587
Hunter 34 Alameda CA
Depending on the length and number of fittings between the source of water (tank or tanks) if something is loose, an air leak even if very small on the suction side could contribute to poor performance. Check to make sure something isn't cracked including the pump head.
 
Feb 26, 2004
21,898
Catalina 34 224 Maple Bay, BC, Canada
I can tell just from visual observation that the water delivery side of the system is a poor, inadequate design. .....
.....
.....

You are right. I should start at the tank and work my way forward. However, your anecdotal testimony is that the delivery side is adequate and I'll take that into consideration, despite my suspicion that it is not. Perhaps it is a subjective matter. I may have an expectation that the pressure should be stronger than I found it to be last season.
Scotty, it is truly tiresome that when one finds a problem, the first thing outta the box is: "...a poor, inadequate design..."

That system has been installed on Catalinas since they started making the C30 before many of us were old enough to buy boats.

I can't begin to tell you how many of us have cleaned out the screens in our faucets, both on our boats and in our homes, and solved the "...poor, inadequate design...", for example.

Your "expectations" notwithstanding, it might be wiser to follow the science.

Good luck.
 
Feb 26, 2004
21,898
Catalina 34 224 Maple Bay, BC, Canada
@Scott T-Bird

Just occurred to me: if you have two water tanks, is one of the two manifold valves closed? Our combined experience (personally and on boating forums) over many years on many different boats is that the system is affected poorly if both are open even with full tanks.

Another: every single domestic pressure water pump has a manual which always includes a very good troubleshooting guide.

Good luck.
 
Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
Scotty, it is truly tiresome that when one finds a problem, the first thing outta the box is: "...a poor, inadequate design..."

That system has been installed on Catalinas since they started making the C30 before many of us were old enough to buy boats.
Stu, let me give you 6 basic rules of pump piping. I didn't come up with this but it does reinforce my basic engineering knowledge of fluid mechanics.
1. Keep suction piping as short as possible. As it turns out, the bow tank is at the furthest position away from pump inlet within the entire system. The stern tank is closer, which explains why my experience is that the system has slightly greater pressure when operating from the stern tank. Yes, I open the tanks independently and don't combine the 2 tanks. I've heard that among other Catalina owners as well.
2. Pipe diameter on suction side should at least equal but preferably be one size larger than the pump inlet. Thus, a better design is to utilize a 3/4" pipe rather than 1/2" pipe on the suction side. Catalina does use "15 mm" pipe but I don't consider that to be one size larger.
3. Use an eccentric reducer on the suction side. I'm not sure if this is readily available, but I'm not going to make a big deal over this issue.
4. Eliminate fittings/elbows on or close to the pump inlet. Each fitting contributes collectively to the friction head on the suction side. I can't tell you how many fittings are immediately in front of the pump inlet. There seems to be about 6 to 8 elbows altogether right in front of the pump because the pump is oriented in such a manner that the pipes, where they come together from the 2 tanks with valves for each, and have to be turned multiple times to get oriented. It's a very poorly designed layout.
5. Eliminate the potential for air entrapment - keeping the tanks above the pump and eliminating high spots in the suction lines is the goal. This is very difficult on a boat, nevertheless, it qualifies as "poor design" even if it can't be helped.
6. Pumps shall never support the suction or discharge pipes - this is why SHURflo specifies that flexible lines should be connected to the pump at both the inlet and the outlet side. Catalina installed the pumps with rigid lines at both connections, and the lines are locked down with holding mechanisms. Sure, it all looks neat and organized, but again, poor design.

Here is another quote from my source:

"Keep in mind that increasing the performance of the pump will help to make up for piping mistakes made on the discharge side of a pump. Problems on the suction side, however, can be the source of repetitive failures, which could cause problems for years to come if not addressed appropriately. Suction side piping problems cause the majority of pump issues.

Piping design is an area where basic principles are frequently ignored, resulting in increased vibration and premature failure of the seals and bearings. Incorrect piping has long been disregarded as a reason for these failures because of the many other reasons this equipment can fail. Many experienced engineers may argue that pumps with incorrect piping still function and operate as they should. This argument, although valid, does not make questionable piping practices correct."

As I have always known, friction head on the suction side affects greatly the pump performance. The most effective way to improve pump performance is to correct all of the issues that can be improved on the supply side.

Stu, I am truly impressed with the design of Catalina sailboats. I'll suggest that plumbing isn't their greatest priority (and neither is it mine :biggrin:). That doesn't mean that engineering principals don't apply. I've identified a relatively minor issue that I am dissatisfied with in regard to the water pressure at the faucets. I'm glad that you have inspired me to review these issues. I don't really want to change the suction lines to 3/4" because that would appear to be a very difficult job.

After I bench test the pump, I may choose to replace it and I definitely will focus on correcting the issues in #4 and #6 because they can easily be accomplished. We'll see how that works. Yes, I will continue to do the routine maintenance of cleaning the various filters on the pressure side to eliminate clogs as you assume have been neglected. :cool:
 
Last edited:
Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
Also, there is a very simple reason why drawing from 2 tanks concurrently is less efficient that drawing from each tank independently. When you are drawing water from 2 sources, you are not increasing the output, but you are dramatically increasing the friction losses on the suction side because the source is flowing from 2 pipes instead of one. You have friction loss from 2 pipes instead of 1 so the length is longer. The longer the length, the greater the friction loss. Friction losses kill pump performance.
 
  • Helpful
Likes: Ward H
Feb 26, 2004
21,898
Catalina 34 224 Maple Bay, BC, Canada
as you assume have been neglected.
You might be confusing me with someone else, Scott.

Anyway, thanks for the primer. Ahem...I spent 45 years in the HVAC, plumbing piping design and installation field, professionally, I'm a registered mechanical P.E. So thanks for that, anyway.

Quite frankly, none of it has anything to do with your issues. Nor with your "diss" of Catalina's plumbing design.

System pressure to be overcome has nothing to do with whether it is on the suction of outlet side of a pump; one adds the two to determine the correct pump selection.

Eccentric reducers are used in building piping pump systems, sure. They are simply unavailable in the marketplace and useless and unnecessary in the low flow low pressure boat systems. A red herring, or that other term...used a lot on CF. Not worth the typing...

#2 is also unnecessary if the pump is properly selected. Same for #4.

I agree completely with you on #5. But only for displacement pumps which don't have a suction head. Diaphragm pumps can suck uphill all day. Most domestic pumps aren't diaphragms. I doubt the bottom of you bow tank is below the pump. If it was, when using that tank, once partially empty, it would never work.

#6 is also useless for this discussion as far as YOUR issues are concerned, but it is certainly good practice, and why some of us think hard piping on a boat is a waste of money.

So thanks for the inapplicable education.

Good luck in your troubleshooting. Just stop shooting the builder.
 
Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
Stu, you are so funny. You don't even comprehend what my "issue" is but you continue to argue, over what I don't even know. I'm also a P.E. for close to 40 years so I'm not completely clueless about how to investigate these systems. You seem to think that looking at the supply side is fruitless, yet it is certainly an important part of the system. I don't really even know what you are suggesting. Your replies can be so abrasive that they are essentially useless. I didn't mean to be condescending in posting on the 6 basics. I simply was pointing to some valid considerations. In turn I think you become increasingly condescending and abrasive. Be my guest if you want to escalate.

And based on my experience, when the supply side isn't adequate, these SHURflo pumps struggle to function properly. Even Ralph said to start at the tank and work forward and I appreciate his comments ... it sounds like a good plan to me. As for shooting the boat builder, I hardly think I was being overly critical. It's a boat so I understand there are design limitations. I'm merely pointing out the factors that could be leading to pressure problems. I think the emphasis of my posting above is pointing out that the suction side is the source of the majority of pump problems. Perhaps I'll be happy if I simply get a new pump. Afterall, the article does point out that issues are often resolved simply by upsizing the pump ... at the cost of working the pump harder than it needs to. Who knows, perhaps if Catalina simply increased the pipe size marginally on the suction side, these pumps would last forever. It's not like they are working hard at all, yet still they seem to have a limited service life.
 
Jan 4, 2006
3,820
Hunter 310 West Vancouver, B.C.
I didn't come up with this but it does reinforce my basic engineering knowledge of fluid mechanics.
Very well put together Scott, and exactly our first thoughts when we design a pumping system for a new refinery or power generating plant. We also need numbers when we go into a plant as a repair team.

But you've omitted the single most important item which should be at the top of your basic rules of pump piping. The need for the acquisition of numbers ........ data. Not a very good list when you didn't pick up on that requirement and yet, are continuing without knowing a single number. None. Nein. Nada.

Good luck in your troubleshooting without the benefit of data.
 
  • Like
Likes: Scott T-Bird