Chlorine Tablet Many Uses

[Pete]

Have read on this forum and elsewhere about the use of pool tablets in tne AC sea water strainers. Had to replace a hose on one of my units last week and when I removed the old hose there were a few mussels inside the hose. So last time I was in Wally World, I got some Aqua Chem 1" Stabilized Tablets that are basically Chlorine. Anyone using these with success to fight off the mussels in the AC system? Also, what about the engine raw water system? Any value to adding one or two to the engine intake strainers to flush that system? And finally, is there a down side of using these tablets, possibly an interaction with some metals in the cooling systems? Would appreciate your experiences and advice on the subject. Thanks

 

[Genesis]

Chlorine will slowly erode metal piping systems; exactly how much of a problem this will be is unknown, but the possibility does exist. The biggest risk is the potential evolution of a pocket of chlorine gas when the unit (whatever it is) is shut down.

Specific precautions are taken to avoid this risk when tablet feeders are used in residential pool applications where a heater is present. Specifically, the feeder must be located so that backflow into the heater core cannot occur, and evolved gas cannot end up back in the core when the pump shuts down. If you fail to take this precaution the heat exchanger can be eaten in a relatively short period of time.

Of course there's no way to prevent this from happening in a boat. I know its an enticing idea, but personally, I wouldn't do it.

 

[Boss Lady]

Just run some ospho through it. that will take care of the mussels!

 

[CARL GUZMAN]

Any ospho left out there tonight

 

[Liquid Asset]

Unfortunetly in our marina if we do not use bromine tablets in the strainer, we are acid flushing our a/c units on a monthly basis. we have bad algae growth, but do not have much hard growth.


I use the small 1" hot tub tablets you can purchase at Wally world. I use 2 in my strainer weekly as does everyone in our marina because of these issues. They prevent soft and hard growth. I am sure that if it was that big of a issue, we would have heard about it, yes it erodes the metal slowly, but how about acid flushing montly because your coolingn tubes are pluged so much you can not get water to go through them?

 

[Pete]

Need a little chemistry education. Looks like chlorine (pool tablets) and bromine (hot tub tablets) are readily available. What are the pros and cons of these two alternatives to keep hard and soft growth out of the plumbing? If there are still better choices, please include those also. Thanks

Pete

 

[Genesis]

They are both halogenated compounds. The pool chemical stuff is just made convenient and includes "stabilizer" (Cyanuric acid); that's important for sunlight-hit pools but of no consequence in this case.

In THIS use, there is no material difference between bromine and chlorine. In pool use there is quite a bit of difference, the biggest being that once you use bromine you're stuck with it unless you COMPLETELY drain the pool and refill it!

The potential problem with these chemicals is that they can evolve more agent than can be absorbed in the water, which leads to free gas in the system when its shut down. Free chlorine or bromine gas is extremely corrosive to almost all metals.

It requires about 8ppm to "inactivate" biological processes, and over long periods of time that is enough to kill biological things in the water. This sort of thing works because the water is basically poisoned enough to keep things from being able to get growing in the pipes. This is a common and established way to prevent biological fouling of piping in various industrial processes that use raw water, and properly controlled it works with little or no risk to the piping or the environment after discharge.

The issue using it this way is the lack of control. If you get free gas (chlorine or bromine) in the system after shutdown and that gas ends up in a metal pipe, you can expect severe damage. I have seen copper feed pipe into a pool filter completely eaten through within a couple of years by improper tablet feeder installation!

If you're going to use it pay very, very close attention to your strainers and baskets (where you're going to put the tablets) and I would also, if possible, put a riser loop in the piping to prevent any evolved bubble of gas from ending up in places you really don't want it (like in your A/C condensors!) Basdically, the loop traps the gas bubble in the hose - while it will degrade the hose pretty badly too, hose is a lot cheaper than an AC condensing unit!

Expect to change that riser loop of hose out every year.....

 

[luckydave215]

Perhaps one of you enterprising industrialists needs to develop a flow sensitive metering pump like the ones used in hospitals to administer medications in IV drips. Couldn't the concentration be monitored through a no-moving-parts sensor similar to a lambda o2 sensor? I'm a mechanical designer, not a chemist. The pump design is straightforward, but I don't know about the sensor.

 

[Genesis]

Metering it via simple suction would work but then you have to keep liquid chlorine on board, and that stuff is pretty nasty if spilled.....

 

[bobk]

Perhaps one of you enterprising industrialists needs to develop a flow sensitive metering pump like the ones used in hospitals to administer medications in IV drips. Couldn't the concentration be monitored through a no-moving-parts sensor similar to a lambda o2 sensor? I'm a mechanical designer, not a chemist. The pump design is straightforward, but I don't know about the sensor.

I too would not put chlorine or bromine into the system at more than one or two PPM. If you really want to do this, you can get feed back controls from pool supply houses. They are ORP meters, that is oxidation reduction potential, tied to small pumps. The problem is what they measure is very sensitive to pH so controlis going to be a problem.

How about a way to give the unit a small dose just before you shut it down for the week?
Bob