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Started 03Jul2025, updated 17Aug025 (wire → rope). In work. This note belongs in group HOBBY.

Standard disclaimer.

Summary

(Se også Sammendrag.)

We got a new grinder pump because the old one wasn’t working properly anymore. The new had higher pressure, which I didn’t notice until after a while, when I saw that at the end of the flushing period a little came out through the vent pipe on the outside of the wall. The vent pipe had been without a valve, even though the sink had such a valve, so that nothing could be forced up into the sink’s water trap. But now the vent pipe had become too short, where it went inside the wall connected to the pressurised pipe on its way down and out, but this one for air – up and mostly out (no, only in!). For this I now had to insert a valve in the vent pipe too. Here nothing should come out! Only the necessary sucked air – in.

I found an ABS plast pipe with a diameter of 32 mm, similar to the one in the wall, and a thinner one, and adapted them both to thinner dimensions. This was to become a valve to fit into «pipe 3» on the wall. Pipes 1 are the innermost, pipe 2 the outermost. Pipe 1s + 2 + coin, became a «good enough» (?) functioning valve. I lubricated my new valve with Teflon grease and pushed it in. The visible part is the outer part with a rope «handle» that I can use to pull it out again. And a tube of styrofoam for insulation from frost.

Then I have to hope that the valve will function. And that it will not freeze and clog up in the winter. If it does, the air will be sucked through the water trap in the sink, with an accompanying «blubb-blubb-blubb» sound. Good warning that the valve is clogged!

If it turns out not to be good enough, I will find a shop and buy a ready-made and 100% tight valve and mount it in the tube. There has to be a valve there with the more powerful grinder pump. Having a look around it’s easy find check valves with disc and spring, but it’s harder to find one that’s based on gravity and not a spring. I fear that with a spring, the valve in the sink would easily open instead, which is not wanted. I assume that a spring would hold back more than the weight of the disc in the valve below the sink in closed position. It has to be the opposite. The valve in the wall must open first. Anyhow, for all the examples I found I would still have to figure out some way to fasten it.

Disclaimer: I am 1000% amateur on this. Follow my work flow at your own risk!

Fig.1 – Finished?

There are three tubes here, I call them ‘1’ to ‘3’:

1. The inner black tube. Cut in two for one in each end
2. The outer white tube. This plus 1 form «my valve»
3. The tube in the house wall that my valve fits into

The bronze disc hangs freely on the sloped tube and is normally closed by gravity. The disk is an out of use Norwegian 5 øre coin. I sanded it on one side to make it even. The disc closes onto the inner tube, serving as a primitive gasket, and swings to open on a copper nail when negative pressure (suck) to let the outside air through. The disc has enough free movement when my valve is pushed inside tube 3.

At least for fast, dynamic pressure as here, the closing seems to be good enough.

Before inserting my valve into tube 3 I applied some Teflon grease on the outside. It may then be pulled out at any time. The friction is high enough that I need no screws or fastening.

Fig.2 – Shrimping a tube

I found a 32 mm ABS tube equal to the one in the wall. (I think it’s ABS thermoplastic. It may be melted and formed again as opposed to shrink wrap which shrinks only once.) The problem was that I needed a tube that fit inside this tube.

So I spilt it in two and used my Proxxon 27070 «FET» saw (German for «Feinschnitt-Tischkreissäge» or fine-cut table saw) to gradually cut off the centre part on the one, and on the other I cut the ends, at equal depths. This way they hold onto each other, making the concept better. But placing them together gives me no circular profile. However the deviation from a circle inserts a «holding onto pressure» when inserted into tube 3. The ABS plast is soft enough for this.

It was nice to have a piece of tube of the same dimension as tube 3. But when I finally tested this, tube 3 was slightly tighter. I therefore had to do an extra round with the outside part of tube 1.

Fig.3 – A handle

Tube 1 consists of one part in each end. One forms the gasket and the other end holds a handle. I spliced tube 1 with my FET saw and used a sand paper on a sheet to sand it down in diameter. I found out that since this tube wanted to keep itself shut, so to say, this was easier than sawing it with such a «living» structure. It now even pressed against the sand paper by itself. Tube 1 was then cut in two, one inside each end of tube 2.

I cut and filed an aluminium part which I inserted into smaller 5.5 mm holes through both tube 1 and 2. Slightly shorter than the diameter of the whole structure. In Fig.5 (below) I show that I also made a small groove and fastened a cable tie (buntebånd, strips) there. Now I can pull my valve out and not have the end that holds the fastener disintegrate. But then I cannot push it completely into tube 3, which I assume would have been better for frost.

Fig.4 – The disc

The five øre coin had the exact correct diameter. I sanded one side and bored a hole in it and filed that hole into a profile that made the disc move freely on the nail. The nail I made a 90° angle to hold it firmly in place between tube 1 and 2. Then I cut in 1 and 2 with a scalpel to give the nail some movement to make the structure less rigid. However, the movement was too free, the disc seemed to hang onto the nail instead of falling onto the bevelled edge gasket, so I inserted a copper wire ring to make the disc more prone to rest where it should. I think this helped. See fig.5.

But then, if gravity does not accurately close the disc when needed, the inside pressure will press the disc against tube 1, thereby closing it good enough. Thinking it over, I have some times felt that tube 3 was somewhat wet (it’s horizontal for some 30 cm.) indicating that it may at times have served as a parallel to the main system’s over the roof vent, when it carries outgoing ventilation. This is not needed, so it’s good to now get my valve mounted to have it serve the single air-in function.

If the disc comes loose, I might be lost. I would probably not be able to pick it out of tube 3, and who knows what might happen if it comes in the way of the water pressure down the drain. However it won’t stop the water completely, which is somewhat soothing.

I collect small screws (196:[S]) so it was easy to find the exact type to assemble tube 1 and 2. This was needed to make «my valve» a single unit.

Fig.5 – Align and lubricate

Even if I did get my valve into tube 3, I got it longer in when I «oiled» it with Teflon lubrication. But even then, not far enough in. So I unscrewed the «pull end» and sanded tube 1 again, from 24.0 mm to 23.5 mm diameter. That’s when I discovered that I needed to add the cable tie.

Fig.6 – Insulate

I had found some rather nice container for this kind of use, which I could use to hold an outer insulation tube made from styrofoam. Right part of figure. I hope this will preserve my valve from freezing. But then, the whole purpose here is to suck outside air in. If it’s freezing cold then I only hope that that air isn’t able to freeze my valve. Better, freeze for some seconds and then melt again. It should withstand the freezing itself, even if it would then not function properly.

Stay tuned. At the time of writing it’s still summer.

Sammendrag

(Norwegian). Vi fikk oss ny kvernpumpe fordi den gamle ikke funket ordentlig lenger. Den nye hadde høyere trykk, noe jeg ikke merket før etter en stund, da jeg så at på slutten av spyleperioden kom det litt ut gjennom lufterøret på utsiden av veggen. Lufterøret hadde vært uten ventil, sjøl om vasken hadde en slik ventil, slik at ikke noe kunne presses opp i vannlåsen der. Men nå var lufterøret blitt for kort, der det gikk inni veggen påkoblet utløpesrøret på vei ut og ned under trykk, men dette med mest mulig luft – opp og ut. For dette måtte jeg nå inn med en ventil i lufterøret også. Her skulle det ikke komme noe ut! Bare nødvendig sugd luft – inn.

Jeg fant et ABS-plast rør med diameter 32 mm, lik det i veggen, og et tynnere, og tilpasset dem til tynnere dimensjoner. Det skulle ble en ventil som passet inn i «rør 3» på veggen. Rør 1 er det innerste (som er delt i to, et i hver ende), rør 2 det utafor. Rør 1 + 2 + en femøring som plate ble en «bra nok» (?) fungerende ventil. Jeg smurte den nye ventilen min med Teflon-smøring og dyttet den inn. Det synlige er ytterdelen med «håndtak» med tau som jeg kan bruke for å trekke det ut igjen. Og et rør med styrofoam til isolasjon mot frost.

Så får jeg håpe at ventilen fungerer. Og at den ikke fryser og tetter seg til vinteren. I så fall vil lufta bli sugd gjennom vannlåsen i vasken, med en tilhørende «blubb-blubb-blubb» lyd. Bra varsel om at ventilen er tett!

Hvis det viser seg å ikke være bra nok, finner jeg en butikk og kjøper en ferdiglagd og 100% tett ventil og monterer den i røret. Det må være en ventil der med den kraftigere kvernpumpa. Da jeg søkte var det lett å finne tilbakeslagsventiler med plate og fjær, men det er vanskeligere å finne en som er basert på tyngdekraft, uten fjær. Jeg frykter at med fjær vil ventilen i vasken lett åpne istedet, noe som ikke er ønskelig. Jeg tenker at ei fjær vil holde igjen mer enn tyngden av plata i ventilen under vasken i lukkeposisjon. Det må være motsatt, ventilen i veggen må åpne først. Uansett måtte jeg fortsatt finne en måte å feste en slik ventil på.

Ansvarsfraskrivelse: Jeg er 1000% amatør om dette. Følg oppskriften min på egen bekostning!

References

Wiki-refs: English: Acrylonitrile butadiene styrene (ABS plastic). Check valve lift-check valve. Disc @ valve. Drain-waste-vent system. Trap (plumbing) Norwegian: Femøring. Tilbakeslagsventil klaffventil. Vannlås

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