We topped up our two starboard tanks a day ago and this morning noticed that the bilge pump had come on. We found that one of our tanks (labelled as a port tank) was overflowing and turned off its tap to the pump. We noticed that when we turned its tap back on, it would start to overflow again - suggesting that it was getting backflow from the other tanks? Is this normal? Did we just top the tanks up too much? Can anyone suggest how we resolve this? Thank you.
Water tank over flowing when tap (to pump) on/open
- Thread starter Ruthine
- Start date
Do you have a manifold that controls which tank you are drawing water from? You should only pump water from one tank at a time.
When you say it is over flowing, I imagine your tank vents drain into the bilge? (Rather than venting overboard near deck level.)
If this is the case, then yes it cold simply be back filling from another tank if the second tank is higher in the hull. Most boats do not have back flow preventer between the tanks and count on using the valves to select which tank you draw from. Some have a central manifold to make this easier.
If this is the case, then yes it cold simply be back filling from another tank if the second tank is higher in the hull. Most boats do not have back flow preventer between the tanks and count on using the valves to select which tank you draw from. Some have a central manifold to make this easier.
Hi Stuart, in the end we shut off 3 of the water tanks and partially drained the two tanks that were overflowing. That seems to have done the trick.
Hey Kappy,Happy to see you've resolved your issue.
We must have over filled the tanks when we filled up yesterday. It was the first time we had filled them (new boat owners - and first time boat owners too) we both expected an indicator for when the tanks were full which we don’t appear to have so did it by eye. Then I guess we expected an overflow if the tanks were too full. If we have them (I think we do - I can see things on side of hull that look like overflow points from the tanks) then presumably they would chuck out the excess? But they didn’t! Instead the excess water was trickling up and coming out of the tank access points and into the bottom of the boat. The bilge pump was also being extremely slow pumping out water so we manually removed the water instead. This might be because the bottom of the boat is extremely dirty - full of gunk and I think maybe the bilge pump was getting blocked?
Tomorrow is a new day so we will investigate the overflow issue then
So yeah we are now in our fav restaurant in Gibraltar. Nice comforting meal and wine.
Hi Kappy,
That is interesting to know. We have four tanks and they were all open. So we have now turned off two of them (when we were draining some water). I guess its something we will keep an eye on from now on… Thanks tho for the tip.
Hi Stuart,
We expected that the tanks would overflow outside (vent overboard) if too full, but they aren’t doing that. However, the tanks were not venting directly into the bilge. What was happening was that the tanks were so full they were leaking from the access caps. One of them was also leaking from the ‘seal’ around the top plate - this had been repaired (poorly) in the past. We did find the central manifold? I’m guessing this is the taps which opens/closes each tank.
Thank you v.much for replying and your advice.
Ruthine
De nada. I have three tanks and only draw one down at a time. If you don't have tank indicators (I don't), this is the only way to have any idea how much potable water remains. Plus, it lets you rotate the tanks to keep them (relatively) fresh. Enjoy Gibraltar - been a lifetime since I was there.
I agree with the recommendation to only open one port on the manifold at a time. If you keep multiple tanks open the other problem you’ll run into is that the pump will start pulling air as soon as the highest tank runs dry, even if you still have more water in a lower tank.
It would be best to fix the leaks on the top of the tank. When we fill our tanks we just put a hose in the inlet and let the water keep flowing until it starts coming out the vent and fill. That’s a lot easier to monitor than watching the fill level and trying to stop the hose when the tank seems to be filling. What are the tanks made of? Unfortunately some plastic tanks are made of a type of plastic that’s hard to get any sealant to stick to so repairs may be challenging.
I’d definitely look into that as it could be a more serious issue if the bilge pump can’t keep up with a minor or moderate leak. (Very few pumps can really keep up with a serious leak anyway.) You should have both an electric and a manual pump; are they both slow? The electric pump might be slow if it doesn’t have good voltage, possibly because of inadequate wiring or corrosion on wire connections.
Thank you so much for this advice. We were initially feeling quite overwhelmed when we saw the water building at the bottom of the boat (new boat owners). The advice and tips you and others have provided are very helpful. Once we had cleared the water at the bottom and emptied the tanks sufficiently we decided to call it a day
Tomorrow will be check and start sorting essential repairs - they are building up!
Just think, one day you’ll have the experience to help answer some other new owner’s questions
. I’d say you’ll be finished dealing with boat repairs too, but that might be a bit optimistic Just think, one day you’ll have the experience to help answer some other new owner’s questions
honestly this popped into my head… One day I hope to be sufficiently experienced to pay it forward and advise other newbies like me… Thank you again David. Unfortunately I know I’ll be posting again on here quite soon… I’m avidly reading my boat manuals and watching YouTube videos. Had hoped the need to learn the boat maintenance would be at a slower pace (first week of being aboard since buying the boat a month ago) but hey ho!!
I think this is your problem. The two tanks you refer to are probably "belly tanks" and are the lowest tanks in the boat. The other two tanks (probably one in the forward compartment and one aft in the boat are above the top of the belly tanks. If your boat is like mine, you probably had leaks from the access point and possibly from the screws on the top of the belly tanks. If you leave all the tank isolation valves with water in the forward and after tank you have a static head that is trying to drain all the tanks into the lowest point, the two belly tanks. If there are leaks in the top of the belly tanks they will flow out those leaks and into the bilge. You need to remove the cabin sole and reseal the access point and the screws. You will probably find that the bottom of your cabin sole may be damaged by the long term exposure. You will also notice that when you overfill the belly tanks till the overflow vent shows water coming out you will have also overpressurized the belly tank and it may even bow up a little from the pressure.
The long and short if it is:
1. Reseal the access point and the screws on the top of the belly tanks
2. Don't over fill them. If you do, immediately open the isolation valve and pump them down to relieve the pressure.
3. Open only one tank isolation valve at a time. Because the Belly Tanks are low in the boat and provide "stability" when full. I normally draw water from the other two tanks.
The long and short if it is:
1. Reseal the access point and the screws on the top of the belly tanks
2. Don't over fill them. If you do, immediately open the isolation valve and pump them down to relieve the pressure.
3. Open only one tank isolation valve at a time. Because the Belly Tanks are low in the boat and provide "stability" when full. I normally draw water from the other two tanks.
Hi Smokey,
Thank you so much for this advice. You are absolutely on point with the problem we created by over-filling the tanks. We had to take up the floor (sole) in the salon area when we realised there was water leaking up from the access caps and screws. We then had to drain each belly tank down. Won’t overfill again for sure!!
I noted you have the same boat as we do: Hunter Legend 40.5. Our boat is 1995. Is yours as old?
When we filled the tank we didn’t realise we were overfilling and thought any excess would flow outside the boat (overflow) but that didn’t happen. From your advice, it sounds like we should have overflow points to the outside of the boat (you mentioned ‘overflow vents’). Maybe they are blocked?
Thanks again
Ruthine
Your internal water tanks should be completely sealed - depending upon how they are set up, they should have a vent to allow the air to escape when filling - that vent also works as an "overflow" but it's real function is to allow the air to come out as you fill your tanks and allow air to come in when using your tanks. Depending upon your design setup you may have more than one vent.
While it is a good idea to draw from one tank at a time, it shouldn't be necessary - your tanks and all internal connections should be completely water tight such that only the vent is allowed to breath. In order to know how best to run your water tanks, you need to know how your vents are setup.
I would guess your vent, or vents, are clogged.
dj