[C320-list] Replacing ALL of the plumbing

[John Kivel via C320-list]

Hi everyone,
I’m one season into owning a 1995 C320.

I spend much of last summer sponging out my bilge and trying to chase down a water leak.

The plumbing system is all 19mm Pex, which is not available locally here in Michigan. So every project included an online order and a two week wait.

Has anyone just replaced the whole system with 1/2” pex?
It seems a little intimidating, but it would all be new, I’d find all the leaks and if I had a problem I could find parts at any hardware store.

My biggest concerns are the aft freshwater tank and the head. Access to those areas seems limited.

Thanks in advance for any comments,
I hope this posts correctly!

John Kivel,
Ann Arbor, MI

[Jack Brennan via C320-list]

Replacing all of the lines seems like a lot of work for limited payoff.

I assume you've tasted the water and determined that it's fresh water and not the normal dripping from the stuffing box.

The most likely source for a small leak is the area under the stern berth where the fresh water pump and shutoff valves are located. Fill the tanks, lift the board that covers the pump and valves and watch for water with the pump on.

Another suspect is the access plate on the rear tank. When the valves for both tanks are open, there is pressure that can cause water to seep through the plate. I believe I used some water line sealing tape to fix that.

If the leak is in the galley, you can remove a few screws and take out the doors and drawers. You would be able to see any leak water flowing toward the bilge.

These Whale lines can get brittle with age. I had to replace one in the port stern locker that cracked. It's possible there is a crack where a line is routed and you can't see it.

Whale is metric and not interchangeable with pex. If you have a West Marine nearby, it stocks Whale.

Jack Brennan
Sonas, 1998 Catalina 320
Tierra Verde, Fl.


________________________________
From: C320-list <c320-lis...@lists.catalina320.com> on behalf of John Kivel via C320-list <c320...@lists.catalina320.com>
Sent: Sunday, January 25, 2026 9:27 AM
To: C320...@catalina320.com <C320...@catalina320.com>
Cc: John Kivel <jki...@charter.net>
Subject: [C320-list] Replacing ALL of the plumbing

[mark--- via C320-list]

Following upon Jack’s recommendations, my 1996 320 had a leak in the galley due to a failed hot water connection. like Jack said, remove the drawers and look there. It was an easy fix

[ART HARDEN via C320-list]

To continue with the sink area, check the water heater relief valve on the top. Mine has been leaking this last and it’s on my to-do list to clean or replace. You could try drying the bilge and make sure the water is off and the pressure is out. If you still end up with water in the bilge it’s not coming from the lines, or pressurized water.

Sent from my iPhone

Art Harden
Catalina 320 "Tortuga" 243
E-42
937.885.9380 (o)
937.477.5544 (m)

> On Jan 25, 2026, at 10:36 AM, mark--- via C320-list <c320...@lists.catalina320.com> wrote:
>
> Following upon Jack’s recommendations, my 1996 320 had a leak in the galley due to a failed hot water connection. like Jack said, remove the drawers and look there. It was an easy fix

[John Kivel via C320-list]

Thanks guys,

Last summer it took me a hot minute to figure out how to take the cabinet front off and expose the galley plumbing, but I got there.

Under the sink is vaguely damp, I think that’s the most likely source, but I wasn’t able to actually identify the leak. The bilge fills up relatively fast, but never enough to trip the electric pump That rules out anything above the floor, which I guess would just be the head and the sinks and the forward water tank.

I’m getting the idea you guys think that I should keep ordering one fitting at a time.
Sure seems easier than running all new lines.

Maybe I’ll get in the habit of ordering several fittings at a time.

John

> On Jan 25, 2026, at 10:35 AM, mark--- via C320-list <c320...@lists.catalina320.com> wrote:
>
> Following upon Jack’s recommendations, my 1996 320 had a leak in the galley due to a failed hot water connection. like Jack said, remove the drawers and look there. It was an easy fix

[Greg Arnold via C320-list]

One possible source for a fresh water leak is the cover plate just aft
of the steering pedestal (where you insert the emergency tiller).  Water
will get in there, run down the rudder shaft, then to the steering
quadrant, then drip into the lazarette and run forward to the bilge.

[KEN GEIGER via C320-list]

Hi, you are in Michigan right.  It gets freezing cold there in winter and your boat's water systems need winterizing.  Every spring there are hot water tanks sitting by our yard's scrap metal bin as they are not always winterized correctly.  There are several ways to do it.  We bought our boat with a leaky HW tank.  Check it out.  Freezing can also damage other water system components.
Ken GeigerNorthern Dream 2000 #765on the hard at Georgian Bay 

[Troy Dunn via C320-list]

>
> John


I am confused by your comment about the pump not going on. Were you
saying the bilge pump or the domestic water pump? If the domestic water
pump isn’t cycling then you don’t have a freshwater leak on the pressure
side of the pump. That means your leak is either between the tanks and the
pumps or it is rainwater. If you meant that the bilge never cycles…that’s
odd…eventually no matter how small the leak, the bilge should get enough
water to trigger the pump to dump the water overboard.

Leaks before the pumps are usually either at the input to the pump under
the aft berth and the aforementioned leaks at the inspection ports from
either over filling or from leaving the forward and aft tank valves open
which leads to the aft tank leaking at the inspection ports. When filling
the tanks don’t put the hose in and walk away. Unless your Dock water is
extremely low pressure you will pressurize the tanks and water will
absolutely leak out into the bilge.

Leaks in the galley that seem hard to find are often traced to a leaking
hot water tank.

Good luck

Troy Dunn
Hull #514

[Jeff Smith via C320-list]

Hey John,

I am contemplating doing the exact same thing. I plan to use PEX and shark bite fittings to make connections. I do not want to use crimp rings in case I need to make repairs on the go. My motivation - I think I now have a fresh water system leak because I did not get it winterized before that severe cold snap in early December, and I vacuumed about 12 gallons out of the bilge when I could make time to actually winterize. It is definitely fresh not salt.

Advantages: 1. I do not need to wait for whale fittings if I have an issue. 2. It will be all new.

I hope to use the old 19mm as a messenger guide for the new 1/2” pex for the aft tank. I believe everything else will be relatively straightforward.

The head is relatively accessible from the AFT compartment. You simply remove the “furniture” that is screwed into the bulkhead. I replaced my head, holding tank, and all waste lines last year. That is how I accessed everything.

I will probably replace my non-functioning shower sump pump at the same time.

Good luck,
Jeff
1994, #121

[Mark Seyler via C320-list]

I have used two strategies to identify the source of a leak so slow you can't see the drip when it happens.

One is to set a video camera up near the likely source and let it record for 30 minutes. Then fast forward through the video until a drip is visible. I used the camera on an old phone this way to find a diesel drip that only happened about once every 5-6 minutes.

If the drip is even slower than you can catch on video, or if you don't have a prime suspect source of the leak, you can completely dry the area (in this case, the area under the sink) and sprinkle a layer of baby powder on the whole area. Check after an hour or two, or if necessary, daily, and see where the baby powder gets wet first. Then look uphill from there.

Mark Seyler
S/V Reality,
Catalina 320, #232
New Orleans, LA

[Dave Hupe via C320-list]

I agree about the emergency tiller hatch .... ask me how I know.
Dave Hupe
1994 C320 #32

[Bob Borelli via C320-list]

If the fresh water pump cycles intermittently when all faucets are off ( galley, head, transom shower ) there is a fresh water leak somewhere.
I have used food color first in forward tank, then after drain & clear the tank, add different color in aft tank, to locate fresh water leaks.
Leak could be simple water filter cannister, hose clamp or leaking 'quick connect' fitting.
Galley sink drain baskets leak, hose to fresh water pump, hot water tank pressure relief has leaked.
Over fill water tanks leaks from cover.
Look for simple fix first.

My C320 has original 15mm PEX with Sea Tech / Watt's quick connect 'collet' fittings.
Easy to remove & reinstall if needed.
And several original fittings have leaked or broken.

I prefer 15mm Whale quick connect fittings, no collets, and keep various Whale fittings onboard along with a piece of 15 PEX tubing, red trace reinforced hose & SS clamps.
I have had to replace fresh fittings unexpectedly & glad to have had fittings onboard and not ruin my cruise.

Shop around for the best price for Whale fittings! Amazon, Fisheries, Defender. Quick mail delivery.
15 mm is larger then 1/2", incompatible.
Shark Bite fittings work great on copper tubing in my home. Not for the boat.

I suggest you measure the existing tubing on your C320 and stick with that size.
Changing to 1/2" PEX because easy to buy at H. Depot then order online will ensure problems making connections to tanks, faucets.

Easy to remove sink galley cabinet & aft stateroom drawer cabinet.
I've done plenty of work in both places. Need a good light, some body contortions maybe necessary. But everything is accessible.

Aft water tank 90 elbow could be a problem, try green comet & food color.
The stuffing tube nearby leaks water into the bilge.

Check transom shower tube connections, I've had to replace both after breaks, replaced vanity faucet hose connections.
Sink drain baskets have leaked, replace gaskets here also.

Look at intake hoses and shower discharge hose, one never knows.
And of course the deck emergency cover plate, slip into the aft lazarette with a water hose on slow, wet the area, look up from below.
While down there check the hose connection under the propane tank compartment, rain water gets in here.
Remove the forward vee berth paneling to check the anchor locker overboard drain hose.

I don't like it when the fresh water pump goes off in the middle of the night ( I know turn power off ).
So I have chased several mystery leaks to a unexpectedly successful fix with out replacing PEX tubing but several fittings, gaskets.


Bob Borelli 1995 C320 no. 209 on the hard at Worton Creek Marina, Maryland.



________________________________
From: C320-list <c320-lis...@lists.catalina320.com> on behalf of Dave Hupe via C320-list <c320...@lists.catalina320.com>
Sent: Sunday, January 25, 2026 12:36 PM
To: c320...@catalina320.com <c320...@catalina320.com>
Cc: Dave Hupe <hoop...@yahoo.com>

Subject: Re: [C320-list] Replacing ALL of the plumbing

[Charles Holbrook via C320-list]

I agree with Bob.  Replacing your whole water system to 1/2 inch pex is a lot of work with unnecessary head aches.  I am very lucky because my local hardware store carries metric fittings and so far I have been able to find everything I have needed to fix leaks.  I recommend staying with your older system and find a mail order source for fittings and replacement hose.  You might try an RV dealer near you.  They also carry metric fittings..  
Charlie HolbrookPort Clinton. Ohio 1995 Cat 320 

[John Kivel via C320-list]

Hi Everyone, thanks for the advice.

Let me try to clarify.
When we first looked at the boat it had not yet been launched in the spring, and there was water in the bilge. Surveyor didn’t seem worried about it.

If I sponge it out, get it totally dry, it will fill back up within an hour. You can see a tiny trickle entering the bilge as soon as you dry it out.

If we leave the water pressure pump on, and no water is running, the pump will run about 2 or three seconds every hour. That’s kind of a wild guess . . . I’ve never actually timed it. As a result, we don’t leave the pump on. We just got used to flipping that breaker as a part of opening a faucet.

The water in the bilge never gets deep enough to trip the automatic bilge pump switch. Yes, I’ve tested and replaced to switch.

My assumptions:
Something under the galley sink is leaking…but it may not be the only thing.

If I left the pressure pump on, eventually the water would get deep enough to trip the bilge pump.

The leak is below the surface of the floorboards. Gravity is filling the bilge with maybe 3” of water, but no more than that, that indicates the level of the leak.

There are two T fittings under the sink at approximately that level, those should be the first things I replace.

John



> On Jan 26, 2026, at 8:24 AM, Charles Holbrook via C320-list <c320...@lists.catalina320.com> wrote:
>
>  I agree with Bob. Replacing your whole water system to 1/2 inch pex is a lot of work with unnecessary head aches. I am very lucky because my local hardware store carries metric fittings and so far I have been able to find everything I have needed to fix leaks. I recommend staying with your older system and find a mail order source for fittings and replacement hose. You might try an RV dealer near you. They also carry metric fittings..

[Dave Hupe via C320-list]

John - Don't replace anything that you can see and shows no evidence of leaking. Based on the amount of water you describe,  you should be able to locate the source. 
Your pressure pump should not cycle on its own unless there is a leak in the system somewhere.

Yahoo Mail: Search, Organize, Conquer

On Mon, Jan 26, 2026 at 10:10 AM, John Kivel via C320-list<c320...@lists.catalina320.com> wrote: Hi Everyone, thanks for the advice.

[mark--- via C320-list]

Odd that it never gets deep enough to trigger th pump. Given the 95 has the shallow bilge, I can certainly appreciate your concern. Hope you find it soon.

[Jack Brennan via C320-list]

How is the hose set up for your bilge pump?

On my 1998, the hose runs all of the way back to the outlet for the manual pump at the stern. When the automatic bilge pump ran, all of the water in the hose eventually came back into the bilge. I solved that problem with a check valve, which some experts do not recommend, but I do.

Originally, my boat had a pump located under the port settee, but its maximum capacity was about 200 gallons an hour, which made it useless in any type of emergency. I replaced it with a standard (and much cheaper) pump in the bilge.

The one good thing about the original pump was that it meant only a few ounces of water would run back into the bilge.

Another idea is to understand that the bilge has several out of the way spots where water congregates. If you have drips from portlights and such, the water can end up there. It runs into the bilge when the boat heels or rocks.

[Jeff Smith via C320-list]

Hey John,

Others have mentioned this, as well. Water coming from the area you
describe sounds suspiciously like the water heater. When I had very similar
issues as you described, I removed the cabinet face in the galley, the
drawers, and then energized the pump. I could see it leaking from a rusty
spot on the water heater pretty quickly. That assembly and the drawers are
not hard to remove. Suggest you do so and then energize the pump. You
should see the leak within one or two pump cycles.

Good luck,
Jeff

[surprise thompson87.com via C320-list]

I agree. About to put in my third hot water heater since the boat was new 27 years ago.

T. Scott Thompson
Catalina 320 “Surprise,” #653 (1999)
surp...@thompson87.com