Flushing watermakers with chlorinated water

I currently flush my watermaker using buckets of RO water but would like the flexibility to be able to do this direct from my tanks. These tanks may contain a combination of RO water and/or chlorinated town water.

To avoid damage to the membrane is an activated charcoal canister sufficient to remove the chlorine in the town water? Is anyone taking any other precautions?

not really answering your question, and do not know how big your boat is, but our solution for a flush is that we have a dedicated 7 gallon tank that we put the first product water in when the WM is first turned on and then use that water for the flush at the end of making water for the rinse.

Stabi said:

not really answering your question, and do not know how big your boat is, but our solution for a flush is that we have a dedicated 7 gallon tank that we put the first product water in when the WM is first turned on and then use that water for the flush at the end of making water for the rinse.

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Thanks. That was the second option and may be simpler. I've got plenty of space.

What size is your watermaker? 7 gal/20 litres doesn't sound like a lot of flush water

All suggestions welcome. ?

yes a carbon filter works. That is what the watermaker manufacturers sell and recommend.

Myself, i never take on city water. five years now, not a drop.

Watermakers like to be used. I use mine every day as a stayaboard

What size is your watermaker? 7 gal/20 litres doesn't sound like a lot of flush water
Two 40" membranes; I am not sure if 7 or 8 gallons storage. Storage is two 8" PVC pipe sections held against a bracket with U bolts that minimize the space intrusion. I backwash the media filter with sea water after each session for about 5 - 10 min, and then bypass the media filter for the freshwater membrane rinse. I seawater flush the media filter, plankton, 20 micron, 5 micron for a few minutes at start up, we usually make our water while underway.

Had two water tanks on last boat. One saw nothing but RO. The other a mix on the rare occasions we had to use shore when conditions weren’t optimal for making water. That way always had water for a RO flush. That was a low output DC unit. Current boat has one water tank. The watermaker is a high output AC unit. Will put in a T on the product line to collect water for flushes. Will have another T draw for the flushes. That solves the issue when the unit is in active use. Having only one water tank is a PIA on many levels.
Current unit is fully automatic and part of the program is automatic flushes done at least once a week even if not used. That draw currently is from the one fresh water tank. There’s a carbon filter in line with the draw. Spoke with the manufacturer who said that’s OK. Will see…..
BTW found it good practice to back flush every section of the salt water draw from the machine back to the through hull with fresh. Found that just about eliminated all growth and you got no sulfur smell as well as longer filter life. So fresh water flush the whole system just before making water and again at conclusion.

One problem with the carbon filter is to know when to replace it ! After neutralising a certain amount of chlorine it ceases to be active. I think there is a test kit for chlorine.

Most tell you how many gallons can it handle before losing effectiveness. Agree they are the expensive ones. The media filters are cheap. No way around it even with Caribbean fresh water at 35 cents/g RO water is expensive. Not at all cost effective. We’re going to pay attention to our use pattern for the next upcoming year. Then decide whether to remove the membranes for remote storage and decommission the unit. Have 200 g of fresh but like having unlimited showers, laundry and fresh in the heads. For most (and maybe us) a watermaker doesn’t make economic sense.

Nick F said:

One problem with the carbon filter is to know when to replace it ! After neutralising a certain amount of chlorine it ceases to be active. I think there is a test kit for chlorine.

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Spectra says every six months, no quantity of water specified between changes. That's for a 6 gallon per hour water maker though. I put a fresh one in every year and pull it when I winterize so I only use one per year.

Stabi said:

not really answering your question, and do not know how big your boat is, but our solution for a flush is that we have a dedicated 7 gallon tank that we put the first product water in when the WM is first turned on and then use that water for the flush at the end of making water for the rinse.

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Me, too. And I don't use city water. Make all my water. Year round.

Nick F said:

One problem with the carbon filter is to know when to replace it ! After neutralising a certain amount of chlorine it ceases to be active. I think there is a test kit for chlorine.

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We changed ours annually. We used a KX Matrikx 32-250-10-GREEN filter. It's rated for 6K gallons and maybe we would put through 1500. The good ones and I'm not talking about the $5 ones from a box store, are rated by micron size, number of gallons and flow rate. If you exceed the flowrate of the filter there will not be enough contact time and you won't get the chlorine removal you want.

After a week to ten days away from the dock, the residual chlorine in the city water has gassed off so you really don't need a filter. We went over a year once and never took on City water.

Hippocampus said:

a watermaker doesn’t make economic sense.

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A watermaker buys time, effort and energy. Hauling water is grueling. If at all possible having the freedom unlimted water offers is the value of a watermaker. The unit itself is such a gift. I am beyond grateful for mine.

Even at a dock, if I had to haul out the hose to Seaweed we would be talking 150' (46 meters) of heavy hose. Instead, except when red tide is prevalent, I flip a switch every morning. Mine is the 12-volt Katadyn 40, an older unit. It provides 1.5 gallons (5.5 liters) in one hour for a cost of 4 amps.

Those spiffy faster more powerful AC powered units are great if you require that much water. Aboard Seaweed I don't need that and continue to be delighted with Katy aka the Katadyn.

A watermaker costs money and buys time.

Hippocampus said:

For most (and maybe us) a watermaker doesn’t make economic sense.

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My whole boat make no economic sense.

Just sayin' ?

It's definitely not about economics, it's about practicality. Even on a boat as small as mine, the 80 gallons of fresh water doesn't very far and you have to ration showers and pretty much everything else to be out for a week. With the water maker you have an unlimited supply of high grade water and don't need to consider rationing it out.

The option to do fresh water wash downs and to rinse off outside the cabin when away from the dock only happens if you can make your own water!

Please note I’ve have a watermaker on current boat and the one prior. So have had one for the last 10 years. But it’s definitely a luxury except if off grid and then a necessity.

The need (or desire) for a water maker depends on where you are cruising. After five years cruising in the Sea of Cortez, using our 16gal/hr water maker, I decommissioned it and placed it in storage. Too much hassle.
Our 40ft trawler has a 250gal freshwater tank. We fill it at the beginning of the cruise with bottled purified water brought to the boat by a man who patiently pours the water into the tank. In that part of Mexico bottled water costs about $2/5gals. We use about 150gals in one month and can fill the tank for free, half way down the Baha peninsula. One month later we fill again with bottled water. Total water costs for a four month season is about $150. That is much less than the water maker cost (diesel power, membrane, filter and repairs to the compressor).

YMMV!

GoneDiving said:

To avoid damage to the membrane is an activated charcoal canister sufficient to remove the chlorine in the town water? Is anyone taking any other precautions?

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Yes it is...at least according to the Rainman watermaker guys here in Australia. I used an in-line charcoal filter connected to a hose and tap in my engine room to flush my watermaker. Very easy to set up and way faster than mucking around waiting for RO water to be a produced then storing it outside the water tank. And you can use as much as you want to ensure a really thorough flushing.

These in-line charcoal filters are intended for use before a drinking water faucet in places where the town water supply is heavily chlorinated. Some fill their boat or RV water tanks via these filters, but I think that's a bad idea: retaining the town water's (normally) minimal chlorine levels in the general water tank helps keep the tank water in good order, IMHO.