How Much Water Flow is Required?

[deluxe68]

We have no water filtration on the boat now and will be installing a NSF53 rated filter. Looking at the Pentek microguard as well as the 3M Aqua-Pure. Looking for a whole boat system and would like to know how much flow I really need. The shower will probably use 2 GPM but I wonder if I need that much flow because we have a pressurised accumulator tank. Would a 1 GPM filter be ok for short showers or do I need a higher flow system. And yes, I am set on filtering the shower water.

[sailorchic34]

You'll want at a filter of at least 2 gpm flow rate. I might say even 5 gpm which may help reduce pressure drop across the filter. Really the main issue is pressure drop. You may find that the pressure drop of a water filter will decrease pressure at the shower head too much.

[RaymondR]

And too small a filter might result in very short filter life.

I had a water filter capacity problem on an industrial machine I built and eventually solved it by installing a swimming pool filter, very high capacity and very low pressure drop and long filter element life resulted.

[Adelie]

Get a better shower head. I have a 1.25gpm head in my house. Lever off helps keep the water bills down even further.

[deluxe68]

It makes sense that if I have a 1 gpm filter I will only get 1 gpm out of the shower head. BUT, I have a pressurized accumulator tank after the future filter location. Currently if I shut off the water pump I still have pressure in the system until the 2 gallon tank drains. I am asking if there is anyone here who has a 1 or 1.5 gpm filter for the whole boat and if they are able to take quick showers.

[thinwater]

You may want to revisit filtering that fine before the accumulator. The pump may not like the flow restriction and the accumulator (it's a non-chlorinated water tank) is a place for bugs to grow.

Remember too when cruising that drinking water is only one exposure route out of many, unless you plan to stay on the boat, never meet people, never swim, never eat food that isn't boiled, and never eat out. I wouldn't worry about the shower.

[deluxe68]

Originally Posted by thinwater

You may want to revisit filtering that fine before the accumulator. The pump may not like the flow restriction and the accumulator (it's a non-chlorinated water tank) is a place for bugs to grow.

Remember too when cruising that drinking water is only one exposure route out of many, unless you plan to stay on the boat, never meet people, never swim, never eat food that isn't boiled, and never eat out. I wouldn't worry about the shower.

So I should leave the shower unfiltered?

Edit. Where would you recommend I install a high flow prefilter, before the tank or after?

[Bill O]

Originally Posted by deluxe68

So I should leave the shower unfiltered?

Edit. Where would you recommend I install a high flow prefilter, before the tank or after?

We run a gross filter from the main tanks (home-type filter housing) something like this with a 5 or 10 micron gross filter cartridge to remove the major particles. This is before the pump and protects the pump and plumbing fixtures (seals) from grit. This should be fine for dishes, showering gen. water usage.

For drinking/cooking water, I agree a better filtration system is needed to remove the bacterial contaminants from the biosystem we like to call the "water system". The obvious place for this type of filter would be in the galley.

We have a separate tank for drinking/cooking water that has a separate spigot from the main water supply. Could do the same thing w/o a separate tank with something like the Aqua Pure Under Sink as long as you had enough system pressure to run it well.

Bill O.

[boom23]

My current boat had a whole boat fresh water filter setup installed, but disconnected, when I bought it. It has 2 large filters and a UV light. As I was curious, I replaced the filters and reconnected the filter.

The pressure drop was too large even with new filters and I ended up disconnecting it and installing a galley under-counter filter with a dedicated faucet. Everything works much better now.

I believe I could make the whole-boat-fresh-water-filter work with a larger fresh water pump and accumulator. I decided it is not worth the trouble.

[Dave22q]

Seems to me that chlorination is enough for the non paranoid. In places with questionable water you might want to up the chlorine dosage or frequency.

[Bill O]

Originally Posted by Dave22q

Seems to me that chlorination is enough for the non paranoid. In places with questionable water you might want to up the chlorine dosage or frequency.

Chlorine would work and be the simplest if one didn't have aluminum tanks. No idea what type of tanks the OP has in his Swan.

Bill O.

[deluxe68]

Originally Posted by Bill O

Chlorine would work and be the simplest if one didn't have aluminum tanks. No idea what type of tanks the OP has in his Swan.

Bill O.

Steel.

[Bill O]

Originally Posted by deluxe68

Steel.

Based on this table, adding a bleach solution (sodium hypochlorite) to sterilize a steel tank often doesn't seem like a good idea for long life of the tank.

We have aluminum tanks and even when we take on a chlorinated "city" water, we try to run it through a carbon filter to remove the chlorine before it goes into the tanks. Fairly simple set up w/the same home-type filter housing (mentioned previously) w/carbon filter and a moderate flow rate. The lower flow rate allows the filter to remove more chlorine than compared to a faster flow.

Bill O.