Second Bilge - One Way Valves? Please Advice.

[Mermaid]

We just installed a second bilge pump with alarm and put one way valves on both bilge hoses as advised by the mechanic. (The second bilge was installed with a t to the original pump draining out of one hose but that will be change so that each bilge has its own drain hose as I don't feel comfortable having them both draining off the same hose.) I would like your advice and thoughts on one way valves on the bilges. Is it one more weak point and something else to go wrong, are they worth it or is it better not to put them on? Thanks for your thoughts.

[Wonderinlost]

I have no idea this is just guessing.

I think the one way valve it necessary because you have both bilge pumps going out one sea cock. Is the sea cock above the water line?

If one bilge kicks on you do not want it to be pumped back to the other pump and back in the bilge. Kinda like just circulating the water. Hence the one way valve blocking the bath (path) back into the boat and allowing the water to go out.

I do not know if one way valves are on all bilges. I guess may not be a bad idea depending where on the hull or how high up it is. I suppose if the seacock is to low maybe water can come back in on a severe heel. May not be a bad idea then. Again its only a guess.

Edit: bath ment path

[HopCar]

Try avoid using check valves in the discharge hoses. They reduce the capacity of the pump. With both pumps hooked to the same outlet you'll have to use them.

Remove the check valves when you install the second discharge.

The other time I see them used is when a large pump is installed in a small bilge and the discharge hose holds enough water to cause the pump to cycle on and off. The pump runs, drops the level in the bilge, turns off, water in the hose flows back into the bilge and starts the pump again. A check valve in the discharge can interrupt this cycle.

A better way to deal with this is to raise the big pump a few inches and install a small pump in the bottom. The hose from the small pump shouldn't hold enough water to re-start the pump when it runs back into the bilge. With luck the big pump will never be needed but it's there if the small pump can't keep up.

[SV Windrush II]

I was sailing off shore when one of my check valves stuck open causing a moment of excitment when I saw water rushing into the bilge as fast as I could pump it out until I realized it was flowing back through my pump. Check valves are advisable in a sailboat because your seacock will be under the waterline on a tack. Just make sure you keep spares in the boat and have a way to easily replace or clean them out if needed.

[HopCar]

"Check valves are advisable in a sailboat because your seacock will be under the waterline on a tack. "

I'd rather see that situation handled with a vented loop higher than the heeled waterline but sometimes you can't get the loop high enough and a check valve is needed.

[CarinaPDX]

FWIW the first thing to do as you said: separate exhaust hoses. If they are joined, then the capacity of hose after the join must be large enough so that both pumps can work at full flow in parallel (ABYC requirement). The hoses should always come up well above the actual waterline at some point under all conditions. And the exhausts should never be below the waterline due to the possibility of backflow. Also, this creates back pressure which reduces the pump's performance.

The check valve is secondary to those considerations. I have to have them because my bilge is deep but small horizontally, so the quantity of water in the hose is enough to restart the pump if it drains back. Even without that concern the bilge remains drier if there is a check valve low in the hose or in the bilge strainer for a remote pump. It would be interesting to know how much that extra resistance affects flow - my guess is that it is small but not negligible.

Greg

[sailvayu]

The OPs install is not recommended. It is not good to T into the same thru hull or use check valves. Check valves can reduce flow by as much as 50%
For your pumps to work well the installation is critical
Here is a video I did explaining bilge pumps:
Understanding Bilge Pumps - YouTube

[HappyMdRSailor]

Everybody's stated the right information, mostly Hopcar Summarized here:

Get rid of the T as planned, 2 lines... Get rid of the check valves... Increased head pressure and debris failure are not a possibility, but a certainty

Raise your discharge loops high enough to keep them always above water level

Simple stuff...

[HappyMdRSailor]

Originally Posted by sailvayu

The OPs install is not recommended. It is not good to T into the same thru hull or use check valves. Check valves can reduce flow by as much as 50%
For your pumps to work well the installation is critical
Here is a video I did explaining bilge pumps:
Understanding Bilge Pumps - YouTube

+1

[SV Windrush II]

Originally Posted by HappyMdRSailor

+1

Ok now you guys got me ripping my check valves out and putting in loops, hahaha

Thanks for the info!

[sailvayu]

Here is the article that goes with the video in case you would rather read about it
Getting the water out - Ocean Navigator - Ocean Voyager 2014

And yes this is a shameless plug but I think the info is important.

[HappyMdRSailor]

Originally Posted by leightonyachts

Ok now you guys got me ripping my check valves out and putting in loops, hahaha

Thanks for the info!

Hey man, you bet!

There are a BAZZILION worse configurations of things on a boat! Sure this one's kinda up there in importance though...

Just sit down there and think about heeling angles and water line for a few minutes... Additionally... If the check valve is to stop pump cycling, as CarinaPDX has... a small secondary or usually "thirdarary" is the way to go...

[HappyMdRSailor]

Originally Posted by sailvayu

Here is the article that goes with the video in case you would rather read about it
Getting the water out - Ocean Navigator - Ocean Voyager 2014

And yes this is a shameless plug but I think the info is important.

Shameless or shameful....

[svlamorocha]

Originally Posted by leightonyachts

I was sailing off shore when one of my check valves stuck open causing a moment of excitment when I saw water rushing into the bilge as fast as I could pump it out until I realized it was flowing back through my pump. Check valves are advisable in a sailboat because your seacock will be under the waterline on a tack. Just make sure you keep spares in the boat and have a way to easily replace or clean them out if needed.

IMHO check valves are a bad solution for the "seacock below heeled waterline" problem. Check valves will eventually stop working and the con sequence is so serious so they are not an acceptable solution for this. Either move the thruhull higher or add a proper vented siphon break. There is a ABYC standard that covers this.

By the way, a hose that goes up and down like an inverted U but is not vented is not a siphon break, it is just a siphon waiting to happen whenever the swell gets higher than the top of the inverted U, which it will when the boat heels taking the rail close to the water unless the drain is in the bow or stern...

Been there, heard glu-glu noise of sea siphoning into the bilge after leaving Panama...... Now I presume every ABYC standard has a reason for it.

C

[Terra Nova]

In bilge pump lines:

NO check valves.

No T's.

Use vented loops.