Dual grey/raw water washdown

[AlexLbk]

Hello everyone,
I am adding a washdown to my 40 foot trawler. Since the boat was designed to run on Swiss lakes it has a rather large grey water tank, which should supply enough water to clean the anchor. That said if I ran out of grey water by chance I want to have the ability to use raw water. The design includes separate feeds one from the grey water tank and another from a toilet seacock running to two different pumps. Each pump output will have a check valve and then connect to a Y fitting that will run to a single hose to the anchor locker. The hose will terminate at a quick connect system that will run to a garden hose. The switch in the anchor locker with have three positions: up=grey water pump, middle=all off, down= raw water pump. My concern is the possibility of pressure generated by one of the pumps backfeeding into the idle pump somehow. I am not too worried about cross contamination too much, assuming its minor. I obviously don't want to fill my grey water tank with salt water, but if a little makes it through - no big deal.
Please poke holes in my design. I also would like to hear thoughts on potential pump damage from applying pressure on output end as well as placement of check valves (after the pump, before the pump, before and after the pump).

[jt11791]

Seems like a lot of effort just to spray grey water. What's the motivation here? Saltwater works fine for anchor washdown and grey water is nasty enough that I don't want it on my decks.

[AlexLbk]

Well the motivation is mostly not to leave a salt covered chain in the locker that will smell and corrode. My thought was that a bit of soap in grey water will keep the anchor clean and salt free and eliminate any type of smell. I am always open to constructive criticism though.

[gonesail]

go with a raw water anchor washdown.

[more]

Originally Posted by AlexLbk

salt covered chain in the locker that will smell and corrode. My thought was that a bit of soap in grey water will keep the anchor clean and salt free and eliminate any type of smell.

Because you disguising smell saltwater simply sell a boat and buy van for desert.

[jt11791]

Originally Posted by AlexLbk

Well the motivation is mostly not to leave a salt covered chain in the locker that will smell and corrode. My thought was that a bit of soap in grey water will keep the anchor clean and salt free and eliminate any type of smell. I am always open to constructive criticism though.

Well I like the idea of fresh water chain wash, but on my boat the galley sink drains to the grey water tank. I would not want to spray that in the anchor locker.

[markxengineerin]

Grey water is more disgusting than you are imagining- do not do this!

[jordanbigel]

I don't have gray water tanks, being an ocean bound vessel not a lake boat, but I am curious about the motivation of having a gray water tank when you then intend to simply pump same gray water overboard (via the anchor wash down). Doesn't that defeat the very purpose of storing gray water in a tank in the first place?

Also, I would agree with other posters here, "gray" water is disgusting. On my boat, that would include the soap and hair from me shaving, the oily dishwater used to wash the dishes in the galley - in some cases, very oily - I don't see why you would want that crap in your chain locker, I believe it would cause worse smells (and bacteria growth) compared to sea water.

My boat is also equipped with both a raw water wash down pump, and a fresh water outlet on deck. I can use either/or, depending on the situation. If I am out for a short cruise and have sufficient fresh water, I use that to wash down the anchor/chain. But mostly I just use the raw water wash down. To combat smell in the chain locker, we try to remove all the chain onto a dock, wash it with fresh water, and wash out the chain locker with fresh water. Probably should do this more often, but we usually do it every 2 or 3 years.

[JebLostInSpace]

I'll echo the concerns about grey water being too gross for this application.

Could you direct your grey water directly to discharge, thus freeing up the current grey water tank for use in your fresh water system?

If so, the added capacity to your fresh water would be available for a fresh water washdown.

As for the original question about back pressure on the pump, I'm not expert enough to know. Hopefully someone will come along who is.

[jt11791]

Instead of using the gray water tank, you could plumb your shower so that the discharge goes straight to the anchor locker. A well placed nozzle above the chain pile would assure that your chain is as clean as you are, with no additional water usage.

[more]

Originally Posted by jt11791

Instead of using the gray water tank, you could plumb your shower so that the discharge goes straight to the anchor locker. A well placed nozzle above the chain pile would assure that your chain is as clean as you are, with no additional water usage.

For that reason i hate any custom yacht or yacht with low production and high customization.
Doctor helling, driver drive truck, IT make software, butcher cut meat. marine architect and engineer make plans for the boat not butcher , dentist, IT engineer

[Scubaseas]

Gray water stinks. It'll stank worse than a salt rinse. I have a gray water tank on my new to me boat and will be putting in a washdown pump like my old boat. Salt water to rinse off the mud if needed, fresh water rinse after the rode is clean and if not actively cruising. Gray water has oil, soap scum, dead skin and all kinds of stuff that will get into every nook and cranny of the anchor locker. Open up the inspection port on your gray water tank and give it a good sniff. No way i would use it to rinse the rode.

[moseriw]

Funny question. The guy is on a lake and wants to use grey or blackwater to clean his anchor.
How do we salties solve this? With a saltwater pump for our shower during a crossing and to clean our anchor.

So where the f is the problem one can not solve by skewing his head to let the few cells consolidate?

btw. blackwater is very good fish feed! Greywater is the really bad thing.

[rslifkin]

I'd stick with the raw water washdown. If you're worried about smell, add a fresh water washdown to either rinse just a light mist across the chain after you've washed the mud off, or to give the pile in the locker a quick rinse after retrieval. That should be able to avoid most smells without using much fresh water. And avoids any issues with grey water getting nasty.

[Boatyarddog]

Originally Posted by AlexLbk

Well the motivation is mostly not to leave a salt covered chain in the locker that will smell and corrode. My thought was that a bit of soap in grey water will keep the anchor clean and salt free and eliminate any type of smell. I am always open to constructive criticism though.

I don't think you'd have problems using grey water as a wash down.
It does include using dish water, shower water, both of which would have residue in it.
It may cause some odor,
Experiment?
Boatyarddog