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Wednesday, 31 October 2012

RO Machine - Part 3

Part 3 of the build started out on a high.

I checked the seemingly bodged idea of using putty to seal up the sensor mounts…

01-RO Machine.27

Works perfect! Completely water tight!

So i set about wiring up the sensor and power cables to the PS-202…

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Attached the sensors into a bit of a test rig…

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And set about running tap water through them to see what happened. With the PS-202 powered up, sure enough there were TDS readings on the screens. Happily both showing the same thing…

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However, i was slightly confused, as my other instruments i use, namely an inline TDS meter on the RO unit and a TDS Pen, both show the tap water TDS to be around 270. So this appears to be reading a bit low in comparison.

This has sent me into a bit of a whirl of confusion today.

For a reference check i ran some straight pre made RO through it…

06-RO Machine.48

Both scales showed zero…

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I was happy enough with this so far…

Next i combined it into the RO units pipework…

07-RO Machine.46

I then proceeded to prepare the unit in the manner i have been doing for the last several months. Running off the membranes down to around 15TDS before switching the flow into the DI chamber, followed by running that off until it hits 0TDS and then start collecting in the storage tank. Essentially this is what the automated controller will be taking care of in future.

Some of these next images are a little shaky as i had to quickly switch back and forth to capture the numbers passing by…

To start with the “IN” channels on both TDS meters were showing about the same, with as much as i could keep up with the photographs…

08-RO Machine.02

That says 134ppm

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Once 15TDS was hit i switched it to transfer to the DI pod and allowed that to run off to zero. Once it was in full production, i checked the values out.

The inline TDS monitors “IN” channel showed 5, which is the water coming out of the membranes, this is normal, especially with the boost pump running too…

11-RO Machine.19

The “OUT” channel on the monitor, which shows the water leaving the DI pod, was zero, as required…

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Interestingly on the PS-202 both the IN and OUT channels mounted directly alongside the respective sensors of the existing monitor both showed zero?

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I do expect to see a few on the “IN” channel, or the membrane output (depending how you look at it).

At first i wondered if the PS-202 was perhaps more accurate and calibrated better, and indeed the manual says the unit is factory calibrate to 342ppm using NaCl… also known as salt. It also has full temperature compensation and the water running through the sensors was quite cool at around 10degrees. But that's what the temp comp should be taking care of and adjusting the value as if it were 25degrees, this so led me to believe that perhaps the other monitor was perhaps over reading due to not having temperature compensation?

I wont got too deep into the science here, but you can read an excellent article on the whole thing by Randy Holmes-Farley on the following link…

What is TDS - By Randy Holmes-Farley

So I'm currently stuck on what to believe? I would hope the more advanced and more expensive PS-202 would be the bottom line answer… but I'm not so sure at the moment.

One thing i did attempt is a homemade calibration solution using table salt.

After a quick hunt round the internet it would appear 1mg/l of NaCl will give a 1ppm reading. To work to the 342ppm calibration that means i would need 342mg/l. Sadly i don't have a set of scales capable of working down to milligrams!

So i made a solution of 1g with 2litres of RO water, which should give me 500mg/l or 500ppm.

15-RO Machine.53

I checked it first with my handheld tester, the result was promising…

16-RO Machine.46-001

Ok a little high, but this may be down to the measuring of the salt and the water.

So i checked it on the PS-202, in both a static (by filling the sensor fittings) and flowing (by pumping it to and from a jug) and got a reading of about 100ppm less…

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Even more worrying, i checked the other TDS monitor and got about 900ppm! With both standing and flowing being more or less the same…

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This baffled me completely! There must be something very wrong to the solution or the method i am trying. But each test device repeated its results every time i redipped their respective sensors…

This confused and annoyed me, as the pen and the inline monitor both more or less the same numbers for tap water, but are way off with the artificial solution? Even if it wasn't mixed up to any specific quantity id assume a reasonable number match with 10% when looking at each one?

So I've ended up a little stuck here for now while i think it over. It seems wise to purchase a proper calibration solution from a reputable source and take it from there.

I did pick up and start thinking about other parts of the system like the solenoid control, but the bother from the TDS results caused me to loose interest a little!

So i put it down for the day and shall return later with a fresh mind, before i start doing anything idiotic!

Just to finish of, a simple project box will be used to house the solenoids and their pipework, with some external connections to allow the box to be connected into the RO unit…

13-RO Machine.40

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Tuesday, 30 October 2012

RO Machine - Part 2

The RO Machine project is now starting to gain some pace, as i really want this in place in advance for the big fill of my Woodson Reef Tank and to carry out continued tops up, and water changes for my aquariums in future.

Recently i have got my hands on a nice pile of equipment from Osmotics, once again a top notch service from them.

01-New RO Parts.04 

Several key things to move the project forwards…

  • A couple of float sensors for high and low water level monitoring in the storage tank.
  • A HM Digital PS-202 TDS Controller
  • A diaphragm pump that will be used to transfer water from storage to the aquariums, and all the associated bits that go with it.
  • A TDS meter for on the fly checks.

A closer look at the PS-202.

03-HM Digital PS-202 TDS Controller.49

05-HM Digital PS-202 TDS Controller.11

Supplied sensors with the PS-202, and power cables.

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I switched out the supplied plug for a UK item and fired it up. Looks all industrial!

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I decided to go with this unit so i can be assured of accurate TDS control. I had experimented with making my own TDS measuring circuits with the Arduino board.

Although i had some success, i wasn't confident it was entirely accurate. So made the decision to have a proper instrument to look after that side of things. I will use the switching outputs of the controller to signal to the Arduino with straight forward high and low signals as to when the TDS is at the appropriate levels.

Going back to Part 1, i purchase various pipe fittings in anticipation of making measurement cells for the PS-202 sensors.

Using a T-Piece…

07-HM Digital PS-202 TDS Controller.53

The sensor would be mounted in the Tee with the water passing through the continuous part.

However the sensors threads are substantially shorted than the Tee, so i have had to modify it slightly.

08-HM Digital PS-202 TDS Controller.44

I have simply cut down the Tee section to the same number of threads and then opened out the lower portion, in order to wind the sensor in as much as possible.

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It’s not the prettiest of jobs but hopeful it will work…

10-HM Digital PS-202 TDS Controller.34

As low as i could get the sensor into the Tee. The electrodes are expose into the flow, hopefully this will be enough. Failing that i will have to try something else.

11-HM Digital PS-202 TDS Controller.50

Reducing bushes added…

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And John Guest connectors for 1/4” tubing…

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Doesn’t look too bad i must admit! (Bar the scuff from the Dremel sanding bit!)

A quick wet test, wasn’t completely successful…

14-HM Digital PS-202 TDS Controller.40

The reducers and the John Guest fittings are absolutely fine. But under pressure, a tiny amount of water was making its way out of the threads of the sensor.

The fit was a little loose and i applied liberal amounts of PTFE tape and tightened them as much as dare, but still got a tiny spurt.

So i worked how to seal them, considering glue and silicone, in the end i reached for a piece of D-D Reef Putty. As this stuff goes pretty rock solid and can potentially stop leaks… even when wet.

I'm not entirely sure if this was a genius or stupid idea as of yet, but we will soon find out when its had time to cure!

15-HM Digital PS-203

More tomorrow on the second test!

Aquarium Tools: Handheld TDS Checkers

A good piece of kit to have available when looking after you aquariums is a handheld TDS checker, sometimes called a TDS Pen.

These electronic measuring devices allow you to quickly check the TDS value, and possibly other parameters, of a water source.

They can be purchased for as little as £5 if you look around, but i would recommend spending a little more and go for a quality and well known brand such as HM Digital. Their TDS Pens retail between £10 and £20 depending on the model.

They are excellent for doing a quick reference check on your RO water before you either add it to an auto top up, or set about preparing it as salt water. If you do not have your own RO unit and purchase your water from a fish shop, they are a great idea to just double check that the shop is selling you good quality water. Unfortunately it is an often occurrence where a shop will sell a customer “Zero TDS” RO water only for it to have astronomic levels! Some say they have been fobbed off with regular tap water, others blame exhausted membranes or DI resins. You can save you self heartache and wasted money by being vigilant.

I recently acquired a HM Digital TDS-4TM.

16-HM Digital TDS4 Handheld TDS Checker.58

Although i have RO monitors on my RO unit, they don't provide an easy method to quickly check any water i have been keeping in storage, and at the time of writing the 200l container i have to hold bulk RO water has currently been sat for around 3months.

A common question i see on forums is “how long can RO be stored”. Followed by various answers ranging from days, to months depending on the environment and the type of water container, and if its is sealed or not etc.

My water is kept in a run of the mill, cheap, rain water butt from the garden centre. It has a loose fitting lid which i semi reinforced by trapping a sheet of polythene underneath to limit any dust getting in, as some will argue that airborne particles will dissolve back into the water and raise the TDS…

So three months later…

17-HM Digital TDS4 Handheld TDS Checker.57

My stored RO is a still a dead 000! Very happy with that!

And as a comparison, my tap water is…

18-HM Digital TDS4 Handheld TDS Checker.06

Quick, easy, and simple reassurance.

The TDS-TM4, also measures temperature, so works quite nicely as a digital thermometer. Great if you want a reference check on the aquarium or are preparing a water change.

19-HM Digital TDS4 Handheld TDS Checker.02

Excellent tools, a must for all aquarist “tool kits” in my opinion.

Sunday, 28 October 2012

How To: Clean a Juwel Power Head

This can be applied to cleaning any aquarium power head, although this guide shows the specifics for cleaning the Juwel Pump or Power Head found in the Bioflow filtration systems.

This will happen to most of us, and i have definitely seen the question pop up on various internet forums.

"My power head has failed, and will not start!”

This is normally exclaimed when the power has been turned off so the filter can be worked on and then the power head fails to start when switched back on.

There is no need to panic or rush out and buy a new one. For one the Juwel power heads are very reliable and rarely break down, it is more likely that it is full of muck, jamming the impeller.

I have a schedule to clean my own at intervals, but sometimes it does get dirty before hand and then presents the typical start up failure.

Here is a quick 15minute process to get it up and running again.

Start by completely removing the power head from the aquarium and take it to the kitchen sink…

02-Cleaning A Juwel Power Head.25

Separate the pump unit from the holder. You have to slightly splay the two tags with the holes in, then wiggle the black pump up and out of the grey holder. Don't bend the tags too much, or they will snap, only a few mm on each side. The pump may also be in there quite tight, just get a good grip and wobble it, it should eventually free itself and slide out.

Plenty of gunk in and around the vent and the impeller itself…

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Start by removing the impeller, it’s magnetic and slides off the metal shaft by gently pulling it…

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A small bottle brush is an ideal tool…

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Carefully clean around the inside of the impeller cavity, don't put too much stress on the shaft and work the brush around it. Have some warm water flowing into it while you do so…

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Clean the base…

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Now for the impeller, handle it with care and don't be over zealous near the blades as they are only made of plastic, either use a cloth or the brush to clean it up as it’s the film of muck around the magnet that was most likely binding it up…

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Clean as a whistle…

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Now clean out the casing, use whatever you feel is necessary, the bottle brush for the spout and some kitchen towel to mop out the bottom work well…

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A few deposits left behind will not harm it too much, plus the next stages will likely get rid of them…

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Reassemble the power head, then find a container that the whole thing will fit into…

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Add around 100ml of vinegar. White is best, but malt can be used if it’s all you have…

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Dilute with water, enough to submerge the whole power head, but leave some room at the top…

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Run the power head for 5 minutes, back in the sink “just in case!”

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When 5 minutes has passed, tip the vinegar solution away and replace with clean water. Run the power head for another 5 minutes, ideally under the tap, gently running fresh water in…

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Replace the power head in your aquarium and it will fire up first time at full “as new” performance levels!

Clean your filtration power heads and pumps every 3 months, and circulation ones every 6 months to keep them in top condition and performing the best they can.