I am considering fitting non return valves to both my cockpit scuppers as on occasions in rough conditions I am getting water flowing back into the cockpit. The cockpit is deep, and about one foot above the water line. A life -raft is fitted in a cockpit :unsure: locker, so I could get salt water flowing around the bottom.

Any reasons NOT to fit this?

Hi John,
Yes, there can be good reasons to not do this, most related to restricting the flow of water and the increased likelihood of check valves to get clogged with the usual debris that often accumulates on our decks and needs to find its way out. Good water flow out of the cockpit is important, not for the water that occasionally gets pushed up the scupper hoses, but more for the rarer, but more dangerous, occasion of getting pooped and having a full cockpit of heavy water making more likely another pooping with the danger of down-flooding.
We also suffered with wet cockpit floors (up through the scuppers as you described) when there were big following seas or when greatly heeled over and rolled with a big one. For us it was mostly annoying as we would then get salty water tracked everywhere. We “solved” this by using something akin to Dry Decks which allows the odd water to be on the deck and find its way out but we step only on the Dry Deck: so our boots are dry. The decking also traps debris before it gets to the scupper so, overall, water runs out more quickly because scuppers get clogged less often.
As you describe it, I am not sure how the water getting to the cockpit floor through the scuppers could get into a cockpit locker and sit around the liferaft. In any case, water should not be able to get into cockpit lockers as they are almost always open to the interior to the boat, so, if that is the case, I would remedy that.
If you continue to want to install check valves, a quick and easy test would be to buy one, fit it to a hose and time the difference between vacating a jerry can full of water with and without the valve. Extrapolate that to the cockpit volume. I would be interested in the results. Also, inspect the valve to estimate how vulnerable to clogging with deck detritus.
I hope these thoughts help.
My best, Dick Stevenson, s/v Alchemy, Galway, Ireland

Hi Dick, thanks for the feedback. The water ingress comes from exactly the same sources and frequency you describe. It is not a big problem just a bit alarming when it happens, at my age you think at the time, could be loss of bladder control!

The diameter of the pipe work from the cockpit to the sea-cock is 2 inch so quiet large. The length of the pipework is approximately 18 inches and they run pretty straight down, no cross over. We don 't have dirt traps on them in the cockpit. Water runs out very quickly.

The liferaft locker lid hinges opens at the cockpit floor so not much I can do about that. The life raft is in a valise so should have some protection from water ingress. Another design fault is that the engine controls are at ankle height so any water flowing around the floor could get into that, which is a concern. So the judgement is, am I more likely to get pooped than flooded via the cockpit drains.

Hi John,
Understood.
If the raft is designed to be mounted outside, as so many are, I would suspect it to be fine in a locker that gets wet occasionally.
I believe being pooped, a cockpit filled with water, is pretty rare. I can only think of 2 times that has happened to me and both were partial fillings.
I might consider crossing the hoses, but that would depend (among other variables) on how far outboard the skin fittings are in your design.
If you go with check valves, try the test I suggested before installation. It should not take long and might be interesting.
Let us know what you decide.
My best, Dick

Dick thanks for your reply. I have tried to source non return valves but they only seem to go to a max. of 1 .5 inches so little progress. I will try to measure the water flow when back on land later this year before any further action.