Repair HDPE filter tank

[dongiulio]

Hello,

I've been using my pool filter for a while now and suddenly the sand tank started leaking from the bottom.

Checking it I found a tiny leak which I fixed hot welding some HDPE to it.

After short it started leaking again in a different spot.

I'm not sure how to fix it, I was thinking of painting some kind of caulk on the inside of the tank, but I'm not sure what kind of caulk to use that would stick to this material.

Any ideas?

Thanks

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[Teapot1]

Nothing sticks to HDPE but hot welded HDPE. Anything else will just peel.

[Denniswiseman]

To be honest if it leaks in two separate places I would be inclined to replace it asit seems to be failing

[dongiulio]

To be honest if it leaks in two separate places I would be inclined to replace it asit seems to be failing

Thing is that I have two equal tanks, and both have the same problem.

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[Teapot1]

Thats unfortunate, what make are they?
Sounds like more welding or replace if its lower cost.
Usual a blow molding so maybe they have a manufacturing issue, still under guarantee?

[dongiulio]

Thats unfortunate, what make are they?
Sounds like more welding or replace if its lower cost.
Usual a blow molding so maybe they have a manufacturing issue, still under guarantee?

The confusing thing is that I had one operating for a couple of years, then it broke so I switched to the second, which broke on the very same way in just few weeks.

I should probably replace the whole unit with something more reliable.

I'm just not happy to replace without an extent of trying to fix.



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[Teapot1]

Yes understand and I try to repair where I can. Reasonably good at plastic welding. I am midway through making my new filter which has rquired a lot of plastic welding as its made from HDPE.
If you have to replace then using 2 filters is a good idea, often my installations use 2 filters as they are easier to fit in to plant rooms than one large one and offer a larger surface area, also easier to backwash eache one individually for a better backwash.
Good luck and please let us know how you get on

[dongiulio]

Uh, you weld hdpe, I'm really interested in improving my technique. I think it might be my only option with these tanks.

I use a heat gun 300 degrees celsius and just something to push and make the plastic adhere.

I found that tanks for distilled water are hdpe so I cut them in stripes, heat both the stripe and the part with the heat gun then when the stripe becomes transparent I attach it to the tank.

I suspect that my error here is that because of the different thickness the tank doesn't heat enough while my stripe heats to much.

I'm not sure how to balance things and get a decent result.

My gun doesn't fit the opening of the tank so, so far, I've been welding from outside.

The first welding I did feels good, just haven't replicated yet the quality of the first time.

Ideally I'd like to reinforce the whole bottom of the tank, I tried doing it but I don't think I tried the right technique.

Any hints and suggestions are welcome



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[dongiulio]

Yes understand and I try to repair where I can. Reasonably good at plastic welding. I am midway through making my new filter which has rquired a lot of plastic welding as its made from HDPE.
If you have to replace then using 2 filters is a good idea, often my installations use 2 filters as they are easier to fit in to plant rooms than one large one and offer a larger surface area, also easier to backwash eache one individually for a better backwash.
Good luck and please let us know how you get on

The filter is a flow clear from bestway, in the images you can see my welding and the whole filter

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[Teapot1]

The repair looks good!

I think I would be looking for a 2nd hand filter/s on one of the sales sites. I prefer side mounts.

[dongiulio]

So I just reinstalled the tank fixed using some liquid sheath on the inside and outside.

It's holding for now, not sure how long it's going to last, as the tank expands visibly when I start the pump, and shrinks when I shut the pump.
this sounds to me like material fatigue.

Next thing I can try is to coat the external part of the tank with VTR not much to keep water proof (that's from the sheath) but to maintain the shape.

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[Teapot1]

the tank expands visibly when I start the pump, and shrinks when I shut the pump.
this sounds to me like material fatigue.

Sounds much more like the pump is way too powerful for the size of the filter. You do not need that kind of pressure, filter failure being proof.
Either, buy a bigger filter or buy a speed controller for the pump. The filter is the way I would go to bring best dividends but anything you did spend on a speed controller would be recouped in electricity saving and the life of the pump many times over.

[dongiulio]

As expected it broke again and started leaking in few hours.

The thing is that in this system the water or of the filter goes into a pipe to the heat exchanger for heating the pool, the pipe to the exchanger is rather small in diameter and I can't upgrade it because its buried in cement, I think that's what giving the tank extra pressure.



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[Teapot1]

Yes certainly could be. Early on in my career I used to see a large array of burried obstructions and obstructions in general. I am an oversizer rather than anything else. For a customer with a gas boiler heating his pool I used a larger solar heat exchanger and the result was quite dramatic heating wise. Same with filters, i use the manufacturers stated flow rate and halve it because that is much nearer the thruth and actual flow rate. Couple that up with the right sized pipes for the backwash requirements and the whole system works better. Additional costs are quickly recouped. Then its better water, lower electricity bills, and quicker heatups.

Sounds like you should scour Craigs list for some new stuff.

[dongiulio]

Yes certainly could be. Early on in my career I used to see a large array of burried obstructions and obstructions in general. I am an oversizer rather than anything else. For a customer with a gas boiler heating his pool I used a larger solar heat exchanger and the result was quite dramatic heating wise. Same with filters, i use the manufacturers stated flow rate and halve it because that is much nearer the thruth and actual flow rate. Couple that up with the right sized pipes for the backwash requirements and the whole system works better. Additional costs are quickly recouped. Then its better water, lower electricity bills, and quicker heatups.

Sounds like you should scour Craigs list for some new stuff.

Sounds like a reasonable suggestion,

Overnight I thought of a possible solution to make my system work and the limitation of the size of the pipes to the heater (that I cannot change).

I'll split the pipe and use two filters, the smaller one to the heat exchanger and chlorine maker,

the other pump (the one worse tank is currently broken) and use it only for filtering.

I'll need a T junction for this and possibly a couple of one way valves. I'm worried that being the pumps very different in power I won't be able to run them at the same time.

But also my pool has only two plugs for water in and out.

So you think this might be a problem?

Craigslist not really an option here, I'm in Italy, i searched through second hand websites but there isn't much available

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