DIY Slide Valve

[aquaholic]

This is not my idea, I saw something similar on a Youtube pond filter breakdown
video.

I recently bought 3 x 100mm slide valves (knife valves) for my drum filter. They will almost always be in open position and can be used to adjust flow rates if needed for my drum setup.

I was a bit shocked at the price but worst of all, they are bulky, ugly and heavy. Too wide to have the 3 valves sitting side by side in a neat straight line as the drum inlet ports are only 120mm apart. Having them staggered makes it harder to have pipe support. Especially as they are best installed upside down so dirt can't settle in the paddle slot. I'm sure it will be painful getting access if repairs are necessary later. Anyway, to shorten my long winded whinge, I'm posting my DIY version in hopes this can help someone.

The concept is really simple and the parts list short so the total cost is quite low. The DIY slide valve uses a 100mm inspection TEE with the water path entering the bottom leg and exiting the perpendicular side outlet. A 20cm length of 100mm pipe has 15mm removed from its 20cm length so it can be squeezed to fit inside another 100mm diameter pipe. Originally I thought this 20cm sleeve piece would have a hole and swivel to align with the inspection TEE outlet hole but I find it easier and simpler to push or pull the 20cm piece lengthwide along the pipe. So I added a handle from 15mm PVC pipe. Under gravity drainage, it holds water quite well but it's not really a water tight valve.

COST: The price of an inspection TEE piece.

Not only is this cheaper and neater, it's hidden which provides more comfort against malicuous vandalism. (I wasn't able to find a lockable knife valve).

The top of the inspection TEE can be opened for access to the valve. I wanted top access regardless in case pipes need cleanout.

I'm also using this to fine tune my water level, I can pull the internal piece up to where I want the water level to be and excess water will flow out the side to drainage.






The photo below shows the internal sleeve half way up the side port, so the DUY valve is half open here. The internal sleeve would be pushed down (out of sight) to fully open up the DIY valve or pulled up to cover the side port to close the DIY valve.

[aquaholic]

The water path I needed is below.



First attempt was to place bought knife valves near the drum filter. This was very messy.
I didn't bother taking a photo of this.

Second attempt was to place bought knife valves near pond wall but this took up a lot of space.


Third attempt was to narrow the space of 3 knife valves.





Fourth and hopefully final attempt will be to remove all the bought knife valves.
I'll leave that for another time but you can see how much cleaner and simpler it would be with only internal (hidden) adustable valves.

I've also got some knife valves 1.5m from the top of pipes. It's possible to cut a long sleeve but I'm not sure if it's worth the effort.

[BWG]

How well do they seal?

[aquaholic]

It's only early days but they seal much better then expected.
With careful cutting, the cut surfaces on the inner sleeve touch together (see photo below) so the diameter can be very slightly over sized which exerts outward pressure. It's not as fiddly to make as it might sound, the inner sleeve cut surfaces only need to touch at top and bottom to ve effective. (So your cuts can be wonky). However tight enough that a handle is best for moving the sleeve. It doesnt rely soley on the natural curve of pipe to seal.

This DIY valve is fully enclosed by pipe each end so a leak doesn't make any difference but I'm sure a smear of cured silicone would make them completely water tight but possibky even harder to slide.

[BWG]

I wonder if a thin rubber or silicone sheet could be glued to the slide with perhaps silicone glue? A pliable sheet that is soft enough to seal but not too soft to make it difficult to slide.

[aquaholic]

Out of interest, I pulled the pipe off the side outlet and the very worst leak is a slow dribble - almost drip but my situation is only about 50cm below water level and gravity drain (open pressure). Thats not surprising as push fit joins without solvent glue can leak the same amounts.

I'm sure these could be made fully water tight (one of them already is) relatively easy but I'm not a fabricator and it's not worth the extra time and effort for me. Most of the time, these valves are open or perhaps marginally narrowed for fine tuning parrallel flow rates from the bottom drains to the drum. I would use a DEKS/JENCO rubber end cap to seal off if I ever needed a water tight seal for repairs. Simply from a pragmatic position. However hopefully this thread is of use to others. It's criminal the prices of slide valves. I suppose many of us (like me) have lost advanced fabrication skills

[aquaholic]

My sub-concious mind has worked out that a very slight angle on the inner sleeve cuts instead of parallel cuts would give the inner sleeve a marginally wider diameter at bottom than at the top. So the sleeve is looser and easier to slide about in the OPEN position ( predominantly below TEE) but would become very tight on the CLOSED position (middle of TEE).

The TEE joint is slightly narrower diameter than the pipe which is very convenient.

However, I still couldnt be bothered. Someone with a precise saw and time could crank these out quickly as there is a market gap (maybe).

[coolwon]

Any work I do on PVC, I use my small grinder with a thin cutting blade or flap discs.

Very quick and easy.