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uv ballast

How to fix my pond uv

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mick H09/06/2021 14:41:46
763 forum posts
28 photos

When the postie arrived with a replacement uv lamp for my pond I broke off what I was doing in the workshop to fit it....after all it would only take a minute or two. Wrong again. It did not work. The uv tube is new, I have replaced the starter, the wiring checks out for continuity which leaves the ballast. My knowledge of "ballasts" is even less than my knowledge of model engineering. The defective (?) one is a Tridonic EC18 LC501 K which do not seem to be available. How do I establish which alternative to fit. The uv bulb is 9W.


Martin Connelly09/06/2021 15:03:03
2013 forum posts
214 photos

Since LEDs are all the rage now getting hold of a 9W system to rob the ballast out of or getting a spare for it seems unlikely. Having serviced my pond filter yesterday I feel your pain. I bought a new UV tube earlier in the week and when I got access to the old tube the cap and glass had parted ways due to the ingress of water past the seal on the quartz cover tube. I have repaired it in the past but now have had to bite the bullet and buy a new one at quite a high cost (still cheaper than a complete new filter though). As the cost of the UV lamps is also high I don't want another one corroding away too soon.

I'm off to service the indoor tank filter now and hopefully there will not be any nasty surprises with that one.

Martin C

Phil H109/06/2021 15:31:26
426 forum posts
46 photos

Chaps, I have a pond, the water is crystal clear and I have nothing, no equipment, no filters - nothing. Am I lucky - why do you need UV and filters etc?

Phil H

Colin Heseltine09/06/2021 15:46:31
634 forum posts
220 photos

This is an opportune post.

I am trying to find a source for a replacement UV light for my pond filter. The supplier for some reason does not keep spares and cannot tell me where to get one from.

I need a:

8 Watt G5 T8 UV-Type 4 lamp. (its for a PowerC 4500)

Can anyone recommend a good supplier



Steviegtr09/06/2021 15:52:46
2314 forum posts
317 photos

I just changed mine . The new one was fitted & did not work. While stripping down to see if i could see anything wrong, i spotted a micro switch. Mine is a Pondtech combined filter & UV. Unless the UV i situated & fixed in it's position it does not work. All ok now. So just make sure it does not have a safety switch somewhere.


Steviegtr09/06/2021 15:54:21
2314 forum posts
317 photos
Posted by Phil H1 on 09/06/2021 15:31:26:

Chaps, I have a pond, the water is crystal clear and I have nothing, no equipment, no filters - nothing. Am I lucky - why do you need UV and filters etc?

Phil H

Phil yes you are a lucky chappy. I have all sorts of filters etc on my Koi pond & struggle to keep it clear. Especially now the Sun is blazing. Making the green Algae.


Grindstone Cowboy09/06/2021 16:36:35
799 forum posts
62 photos

Quick search found these - no connection with or knowledge of the company.

Links to


Edit - although on further investigation they don't seem to have the wattage you need. May be worth an enquiry, though.

Edited By Grindstone Cowboy on 09/06/2021 16:48:30

DMB09/06/2021 19:58:26
1230 forum posts
1 photos

Has Phil H got pond snails? They eat green algae and are recommended for keeping ponds clean

mick H09/06/2021 20:47:06
763 forum posts
28 photos

I managed to find a company (International Lamps Ltd), that actually assists with telephone enquiries as opposed to email enquiries which are never answered. Anyway, spoke to a knowledgeable chap who was able to tell me that the original ballast is no longer available and suggested an alternative based on the wattage of the bulb.(9 watts). Apparently the original ballast was rated at 18W and probably designed for 2x9W bulbs. He reckoned that this would not help with the longevity of the bulbs which seem to blow with monotonous frequency.

Is UV available from LED technology? Forgot to ask him that.


John Haine09/06/2021 20:56:41
4420 forum posts
262 photos
Posted by mick H on 09/06/2021 20:47:06:

Is UV available from LED technology? Forgot to ask him that.


Yes. Many white LEDs actually use a phosphor illuminated with UV generated by the diode. Also UV LEDs used by dentists now to polymerise fillings.. and have been used for experimental COVID sanitising.

Phil H109/06/2021 21:00:03
426 forum posts
46 photos

I do have snails but if you look at natural ponds (in fields) - you will notice that they are all crystal clear unless the local angling clubs have been there. Angling clubs appear to destroy natural ponds. None of the natural ponds that I have seen have filters and electric UV systems.

As far as I can tell, a pond simply needs a good combination of the right type of plants. Ones at the bottom and ones that have floating leaves. Also, make sure you have plenty of creatures in the water. Having said that, I didn't actually import any creatures and I didn't have any border controls - they are all immigrants and simply arrived all on their own. Frogs, newts, dragon flies, snails, beetles, water boatmen - weird spider things and pond skaters.

Save energy and go natural. Burn the energy on your lathe and miller.

Phil H

Bob Mc10/06/2021 11:26:50
205 forum posts
23 photos

Replacement UV lamps & LED UV lamps.

Mick...there has already ben a discussion about this..see thread

Pond filter with UV lamp


JasonB10/06/2021 12:09:34
21999 forum posts
2539 photos
1 articles

Yes you only really need filters and UV when you are throwing a few handfuls of food into the pond every day, more so on a dedicated koi pond that does not have any plants in it as unlike natural ponds they are not a natural system.

I find I need to run my UV for about 8hrs a day this time of year and have it on a timer and it's plumbed into my surface skimmer line. Filter runs separately on it's own pump fed from 4" bottom drain and runs 24/7. Gin clear down to the full 5ft depth.

As mentioned in the above post we discussed LED UVs recently here and the wavelengths are not suitable for this use.

Edited By JasonB on 10/06/2021 12:11:15

Edited By JasonB on 10/06/2021 12:13:02

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