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Sunday, November 23, 2014

Off Topic: Simple Point of Entry Filter with Backwash and Rinse

Hello readers!

When it comes to the Point of Entry (POE) water filter my journey on Google to find what works hasn't been very fruitful. Sure there are other blog writers and probably some forum which shares their finding after installing one in their homes.

Therefore I've decided to share my findings after I've installed one for my house.

It's been 2 years since I've resided in my current house and I haven't installed a POE filter. From my observation of our Pensonic Mineral Pot which is our sole drinking water filter, the sediments appear to be moderate and only really gets disgusting after about 2 weeks and need frequent scrubbing of the filter to extend its life.

My goal for this Point of Entry Water Filter project is simply to filter out sediments from the water supply and not to improve the quality of the water as I believe the quality is good, after you've filtered out the sediments.

I've consulted several shops which sells the famous FRP (Fiber tanks) and steel tanks canister type filter with sand as the filtration medium but what I can conclude is that the filters they sell don't really work as the sellers thought they would. Long story short, the flow through those canister filters passes through the finest then the coarsest medium, while they thought it's actually flowing through the coarsest then the finest medium. When I proved their misconception, they went silent with no answers. Once I learned about that, I didn't really wanna get one for my house.

Membrane type or brand names like 3M could be really good filters but doesn't fit in my budget.

Ok back to the story, I've decided to get the simple canister filter which strictly filters out sediments in the water. They're cheap and I see them in use in other countries as well. The filtration media is easily obtainable at many shops and also comes with a choice of filtration size ability (10 microns, 5 microns etc.). This is probably the simplest filter to install and is considerably cheaper than other options so I went on with the installation.

Simple canister filter with wound fiber filtration medium

Alright, once I've decided on the filter I tinkered around the configuration. The pipes to connect a filter has been prepared earlier when the house was renovated, so all that's left is to connect the filter.

I thought that one canister may be too small for the job and I've heard feedbacks that a single canister is quite wasteful since you'll end up changing the filter frequently. That being considered, I decided to install two canisters instead, and they'll be configured in parallel. Assembling the filters in parallel will provided larger filtration capacity as well as decrease the pressure drop compared to installing only one canister, or two canisters in series.

For the first try, I opted for the Wound Fiber filter media that if I'm right filters out sediments larger than 10 microns. If this doesn't work well, I can then try the 3 micron Polypropylene compressed fiber filter media.

So, one fine Sunday I began the works:

The first configuration of the installation. With the inlet at the lower left and outlet to the house at the lower right. Water passes both filters and this photo was taken after two weeks of installation. Look at the color of the filter, yucks!

The wound fiber filter after two weeks of installation

While I was installing the filter, I knew that I've never worked on high pressured pipes and the filter connections and the valves were all threaded connections. The elbows, tees etc are all glued connections which is hard to mess up. But threaded connections, must be done right to avoid leakage. Since I'm working with high pressure for the first time, I knowingly know that I'm not gonna get it right the first time and there is gonna be some leaks! 

And so it happened, there were leaks in the connections though some connections were solid. I gave it a real thought on how to make solid leak-proof threaded connections and decided to try again with the method of double threading on the PTFE pipe tape as well as silicone dressing to help secure and seal the threaded connections. 

So while back at the drawing boards, I went a lil way out and decided I wanted to try to include a backwash and rinse function while I'll be reworking the filters. After the rework, here is what I came up with:

This is the product after another Sunday afternoon, the assembly has been reworked with more valves and additional faucets for the backwash and rinse function. I had to leave the assembly for a few hours since silicone sealant is involved and I want it to set properly and not ruin them by flowing and applying pressure too early before the silicone sets

Double threaded PTFE pipe tape; tape once and work it into the thread, take it out and rethread with PTFE and apply silicone sealant and thread it in for good. Works wonderfully, no more leaks!

 The filter after two weeks...

The filters after I gently rinse them with water

Ok you must wanna know how this works so enjoy the three following photos!

Alright, I hope the photos on how it works is pretty self explanatory but I welcome any questions!

Ok, so after the rework I didn't change the filter but as I've shown you in earlier photos I rinsed them gently then reinstall them. After one week of flow I decided it's time to try the backwash function and see how effective the backwash is. Prior to that I have considered the following factors:

1. Flow rate through the Backwash Mode is limited by the faucet which I could install. I may or may not be able to apply as much pressure differential across the filter. Which will dictate the effectiveness of the backwash.

2. The fibrous nature of the filter means it won't be easy to backwash since some of the sediments would be embedded into the filter fibers and hard to remove with backwashing the filter.

3. I didn't add valves to every canister to isolate each canister during backwash, so the backwash flow rate for each canister is roughly the total rate out at the faucet divided by two. There was room to install one but I figure that can wait. By isolating the canisters during backwash, it will maximize flow across one canister at a time instead of backwashing both filters at once.

4. Applying too much pressure differential across the filter during backwash could ruin it since the filter will be 'expanding' as the flow direction is reversed, this could cause the filter to open up an allow larger than designed particles to pass through after backwashing.

Ok enough talk, lets see what I managed to get with the rework:

Overall, I did well and I'm satisfied with the result. The backwash feature works! Perhaps I can take it further by adding a valve to each canister so that I can backwash one canister at a time which will allow larger flow rate across the filter media when backwashing. But for now, back to observation mode...

Did the filter work? Of course, you saw how dirty it looks but I've more pictures to show. My mineral pot filter shows remarkable reduction in sediments trapped. Previously, 3 weeks would be too long to leave it by itself, after two weeks you'd have to scrub the sediments off the ceramic filter on the mineral pot. But after three weeks of the POE filter, there are still some sediments being trapped but most have been filtered out by the POE filter. This means that most particles in the water supply at my area are larger than 10 microns.

Here is the ceramic filter of the Mineral pot, which after three weeks is only showing few days of sediments when we had no POE filter

For my objective for the POE filter, I've achieved it partially. When it's time to change the wound fiber 10 microns filter, I'd like to try the 3 microns filter media and see the results.

Thanks for reading!

1 comment:

  1. Salam tuan Mahfudz. Lama tak dengar cerita. Adakah masih membuat akuaponik?


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