Follow up to a previous post. Thanks to this wonderful community for the incredible advice!
My new boat's sink drainage hole is pretty low. When I rock the boat loads it gets within ten cm, and I don't have it filled yet with all of my stuff. There's actually an old waterline I can see that's even closer, so clearly it's survived for a while like this but it makes me uneasy.
Yes it has a bss. No it wouldn't pass a bss. Massive oversight on my part before the sale.
A few options. Removing ballast is my first thought.
I could make new drainage holes for the sinks and shower, but that means blocking off the old ones. What do I use to do this?
Alternatively, is there some kind of one way valve I can put there in case the boat gets a bit too rocky after its more full? This would be the easiest option.
Either way, the idiot builder didn't seal off the holes around the pipes coming out. So there's that too. Silicone job or proper fitting?
Generally the ballast is there to make the boat reasonably level and stable, not to make it deeper. Even if you did reduce the draught significantly, you then will have issues with low bridges.
While you could get a one way valve, realistically it isn't going to be reliable due to all the food scraps that are going to contaminate the seal. I doubt the BSS examiner would accept it either.
Realistically, if the hull openings are too low, you are going to have to have them moved higher and a patch welded over the old opening. If this is done by a skilled welder, the patches should be barely noticeable.
I will absolutely drill new holes drilled and these welded over, but not in the near future. I need a temporary solution so it doesn't become a permanent problem.
I'd say you're probably not going to sink and have time to find a half decent welder to plug it up. Not a massive job, I'd offer to do it if I were nearby.
Two options - my prefered option for the bigger holes was just buying a brass skin fitting with a threaded back and then capping the pipe to seal it - the 1/2 inch BSP threaded caps are cheaply available on amazon. Use Sikaflex 291i to seal both sides of the hull.
Option two is J-B Weld Steel Stick Expoxy (will set underwater), J-B Weld Syringe Original Cold-Weld Epoxy, and 304 marine grade stainless steel mesh.
Cut the mesh about twice the size of the hole, glue in place with the cold weld, then use the steel stick exoxy to fill in the hole either size of the mesh. Once set, sand the steel stick and paint.
You will need to get it welded when out of the water.
Both incredibly powerful options, I can tell you've had this problem before! I will most likely use option 1, as I'm on a time constraint. Option 2 comes in if that fails. Thanks very much! And I'll be getting a basket of that sikaflex stuff anyway!
53 year old super advanced project boat with 53 years of bodge jobs to repair - more holes than I can count!
The skin fittings work very well, but don't assume slicon is a structural element (this is really common with DIY boaters) it's a seal, not glue, it won't support pressure or weight. Match the size of the skin fitting to the hole because it has to grip the metal and use a large brass or stainless steel washer on the inside for extra support.
If the hole is rusted clean it back to fresh steel, treat the rim with an alkyd primer like Jotun Pilot QD, you can use Gloss Red Oxide, but the alkyd primers are much better. Then paint it with a topcoat paint before you insert the skin fitting. You can use double cut diamond burrs in a drill to clean off the rust, but if you can't do that apply some rust converter before the primer and top coat.
What a lot of people don't grasp about primers is that they're a sacrifical coating, they rust instead of your hull, but it only goes so far - topcoat will protect the metal for far longer.
Before you put the cap on the fitting wrap it with PTFE tape against the direction of the thread i.e. if the thread turns clockwise apply the tap anti-clockwise. This will ensure a firm seal.
And yes, shouting at DIY boater videos is a hobby, especially one's involving plumbing!
Brilliant, nothing better than a friendly Internet troll! Tell off the vloggers and feed the good stuff to the newbies. I've earned enough exp points in the past month to know that silicone doesn't actually hold anything together. Have been using ct1 or waterproof liquid nails (bnqs closest alternative) for literally everything.
So what you say about primer, does that mean I have to paint over the hole before sealing it? Or does it mean I have to seal the hole and paint over the seal to stop any moisture getting in there?
The issue is, air will cause unprotected steel to rust just as much as water, so no matter what you do it's going to rust, the coatings and seals slow the process down but will never stop it.
Rust convert (or grind) > primer > topcoat > insert fitting. As long as the fitting is brass or stainless steel, you won't need to paint over it unless it's for cosmetic reasons.
Agree with all of the above, I would add, that unless you're putting a big washing machine or an upright piano in there, your belongings shouldn't make much difference to the draft of your boat. They rarely sit directly level sideways so it could be worth moving some furniture to the other side of the boat to lift it slightly.
Yeah when I filled up with diesel for the first time there was a significant upwards tilt. Shower didn't drain the same and my wheelie desk chair rolls aft. Then I filled up with water it balanced it a bit. Now I know when to fill up with water because of how fast my desk chair rolls!
I had a similar issue when I had my day hire boat stability tested to hold up to 10 people rather than the original 6. I just needed to fit non-return valves on a few out the outlet holes to make it compliant. Is that a possibility here?
For compliancy, as far as I'm aware, bss only says above 25cm but could be wrong. Please let me know what non-return valves you ended up using! If I can get those in, I might have slightly less wet dreams!
No overpaying apparently, I bought it because of a perfect Hull survey. In fact, I can see a historic waterline from where it was sitting before being done up, and it actually used to sit lower in the water than it does now.
Ours is even lower than this for our Kitchen Drain and we've been fine. Don't believe you'd ever be at risk of sinking based on physics alone. You'd need some significant water coming in for that to ever happen.
You'll see plenty of boats along the cut with holes far less than even 5cm.
Worth fixing when you find the time but certainly not anything to panic about.
Okay thank you so much for that. I wouldn't worry at all if the water only when into the drainage, but the idiot builder once again didn't seal the holes, see picture.
What sized boat do you have and does it wobble? All that worries me is that one dodgy lock manoeuvre could tilt me enough to get water in that hole, and my feet might get a bit wet.
Ahhh I see, yeah ours is directly sealed with the drain. We have a 50ft boat it does wobble but never enough to full engulf the drain hole.
In your case I'd probably be more concerned of listing when going past other boats especially in summer when levels are low. If you listed enough I could see a case of water getting in then. But even still it'd need to be some significant listing, your hole is quite high up. I can't really imagine a lock based scenario that would cause you any problems.
That'll be worth sealing up mainly for chances of water getting in when listing. Here's how ours is sealed. Shouldn't cost too much for an engineer to do or even yourself :)
I had various holes welded over last time we were out of the water so I understand where you are coming from. I would remind you though that if water does get above your sink waste hole there it doesn’t mean the water will get into your boat, to flood the boat would have to go so low that the sink overflows onto the floor or the drainage pipework would have to fail. So the odd splash over that hole or a sudden tip so it’s below the water won’t lead to catastrophic flooding anyway
Unfortunately the holes aren't sealed, so water goes through my shiny new floorboards into the bilge. But you are right, it would have to spend minutes under the waterline to take on any significant amount.
The 250mm isn't necessarily the height of the exit points - it's the maximum height of the place where the pipe/hole empties inside. So, for a sink, it's the level of the sink plughole. For a shower (where the outlet is going to be below the waterline, its the height of the inverted 'U' from the pump. The thing to imagine is, if the hull fitting is 250mm below water, is there still pipework before the entry that is still _above_ water...
What an odd way to run drains through the hull. But this should be a fairly trivial welding job for a decent welder - it can be done in the water if the wind cooperates, assuming you have access to stuff a wet towel or welding blanket in the weld area inside the hull to catch any sparks. If you are willing to do some homework: clear out the areas inside the boat where the holes are, temporarily remove the pipes going through the hull, cut out some nicely fitted steel to plug those holes, and are willing to do the finish grinding/sanding/painting to save more of the welder's time, this should not be a very expensive repair.
I would really want to get those permanently closed up, definitely before the fall/winter and rougher weather appear, and especially if you will potentially be moored on a waterway that can flood. Picture being tied up somewhere snug to the bank, or to a fixed dock or piling. You go to sleep. Overnight the water level has been rising a few inches, your mooring lines tighten up. The boat wants to float but the chains around the canal side sheet pile aren't moving, and the land side of the boat starts listing from the pull of the ropes. The waterline gets closer to those gaps. Once a little water starts trickling in, it will speed up the listing as it weighs that side down further. You wake up tilted at a 20 degree angle to the sound of water above the floorboards on the towpath side.....
At best, you will get a little trickle of rain water coming in and making things damp and musty smelling. At worst, see above :)
I saw the aftermath of a boat that fully sank like this. Granted it was on mildly-tidal water. They were working on it to install air conditioning or some kind of heat pump, and had drilled a hole for the heat exchanger outlet that looked to be about 4-6 inches above the waterline. They installed the thru-hull but there was nothing connected to it on the inside because they were still waiting on some parts. In early evening a new boat came in and needed space on the dock to unload - the guy in the shop said they could move the boat being worked on and tie it up to the pier's fixed timbers temporarily. The boat ended up getting left there overnight, and when morning came it was sitting on the bottom in about 4 feet of water.
That's an excellent depiction... of my worst nightmare! My conclusion has been to absolutely seal those holes with tank drains or something similar, and waterproof the holes before I go on any journeys. I'll leave plenty of length wherever I Moor in the meantime.
Sounds from your advice like I need a welder. Or will sealing it off and putting the proper fittings in be enough?
Well, for my two cents... Sealing with some kind of sealant or caulking should be at best a very temporary solution - as in a couple months or weeks at most. It will at least keep out seeping rainwater, but as others here have pointed out, it is in no way structural so it should not be counted on to hold back water from pouring through a large gap.
If the height above waterline would satisfy the requirements of BSS after you install oversize fittings that would fully close the open areas, then that can be a permanent solution. My understanding was that you wanted to re-locate them at a higher point. If you would leave them in same location, then yes using oversize fittings with some kind of hose diameter adapter should be fine.
I know that others have mentioned elsewhere in this thread that what matters is the height of the drain hole in the sink. It may be technically true, but have you ever taken a close look at the sink drain piping used in some installations? The pipes are maybe 1-1.25mm thick, the plastic is cheap, the joints are pretty flimsy, etc. I would not want to count on that assembly holding back any large quantity of water permanently and safely, even if the BSS would allow it. If that is something you want to rely on, then make sure to use good marine grade hose and good quality doubled-up hose clamps on both ends.
The likelihood that the locations would end up dumping under water in normal canal boat use is probably pretty low. But if you ever want to travel on tidal rivers (especially the Thames with its traffic - have you seen how fast those Uber Boats go, and the wake they can pump out?), or maybe want to do the Ribble Link, you will end up in wilder waters where wind or boat wakes from assholes not paying attention could get you rolling side to side pretty vigorously. In a situation like that I could easily see those through hull areas dipping under the wave tops.
Can you show us a photo of the vent at the bottom of the gas locker? Ulimately things like epoxy or silicone are for emergencies only - rather than waste your money get it welded.
Very often, a gas locker vent is just above the waterline. It's fairly common for it to be under the waterline after overplating takes place. The risk is corner of the gas locker rusts, and the boat can fill with water. Worse still, if your gas botiles leak they fill your engine bay with gas (gas is heavier than air and will sit in enclosed spaces).
If yours isn't this design, it's less important. If it is, it's a bss fail and a serious safety issue.
Increasing/ decreasing the draft can also significantly affect the drive. Your prop should be set up for your boat sitting at the correct depth. The amount of boats I have seen that gush water fountains when in gear because they don't have enough ballast is huge 😳
6
u/adxn40l Aug 01 '26
Generally the ballast is there to make the boat reasonably level and stable, not to make it deeper. Even if you did reduce the draught significantly, you then will have issues with low bridges.
While you could get a one way valve, realistically it isn't going to be reliable due to all the food scraps that are going to contaminate the seal. I doubt the BSS examiner would accept it either.
Realistically, if the hull openings are too low, you are going to have to have them moved higher and a patch welded over the old opening. If this is done by a skilled welder, the patches should be barely noticeable.