Adding a raw water washdown

[vanderd]

Our catamaran has a fresh water anchor washdown. I am in the process of adding a seawater option. I plan to use the same built in hose and just change a couple of valves as necessary. For those times when water is plentiful I’d like to have the option. Locations for the sea water pump are few. My best option put it below the waterline. I’m not sure if this is a good idea and would like to hear what others think
Thanks for responding

[puffcard]

I would keep the pump, just above the water line. If a major failure, you're ok and makes changing the strainer much easier.

Also think about other places you need saltwater. We distributed SW to four places on our 37ft'er. To the galley sink for cooking and cleaning foredeck anchor wash, cockpit for SW showers and great for fish cleaning. Also feed the holding tank to help in flushing.

[vanderd]

Thanks for responding. We can make 400 gallons of fresh water per day (when the darn thing works!) So I’m not really interested in adding salt water anywhere else. It’s very difficult to mount the pump above the waterline but if Not doing so is a bad practice I would want to avoid it.

[James S]

Ill be adding an anchor wash down when i get back to the boat so been giving it lots of thought.. I'm not a big fan of below the waterline thru-hull fittings .. as of now we only have 2.. one for raw water cooling and a second one next to it for future AC cooling line..
My thought/hope is that my wash down pumps inlet will be a hose that I toss over the side from the bow when I need to use it.. Pump will be installed below deck..
Just a thought..
As for installing the pump below the waterline goes.. the pumps I've been looking at seem pretty robust as far as catastrophic failure goes.. but connections to and from them and seacock is another story and obviously potential week link.. Im pretty anal about closing my seacock when not in use.. if you do the same with your seawater wash down inlet then no problem..
The only other concern id have is possible cross contamination if you plan to have fresh and sea water connected via valves... I'd go way out of my way to avoid any possibility of that.. even if it means a whole and separate system..
I'm sure there are some back flow preventers and other ways to avoid cross contamination.. but for my money.. limited mental capacity and general belief in Murphy's law.. I wouldn't take the chance in contamination of my "survival" water... but like I said.. I can be a bit over the top.

[daletournier]

Can't you just turn the sea cock off? My pump and seacock are under the front head vanity. I see the hose to and from the pump as no more likely to break than any other through hull hose. The actual coil hose and gun I do see as a weakness. I switch the breaker off after use each time.

[RaymondR]

The small pressure pumps generally used as wash down pumps don't have a problem with priming and can be mounted well above the water line.

I would not mix the systems unless you have a number of fresh water tanks. If you do use a three way ball valve on the suction to the wash down pump rather than two separate valves, that way you don't run the risk of having both valves open and cross contaminating your fresh water.