Soft close solenoid valve for DIY fox scarer?

[letshaveit]

I finished making my fox (and cat) scarer using one of those noisy impulse = water sprinklers. This is controlled by a PIR which activates a 12v soleno= id valve connected to the garden hose that then connects to the sprinkler.

It works a real treat but the problem is that solenoid slams shut instanta= neously. This sends a shock wave back through the water system. And the res= ult was that the shock waves caused a water leak at a junction of the incom= ing water supply from the street.

My question is to find out if there's an easy way to overcome the shock wav= e problem - either by:-

1. Electrical solution to close the solenoid progressively - whilst still = making it open instantly. or
2. Some mechanical means in a pressure vessel or whatever?

All suggestions are welcome.

[Harry Bloomfield]

[e-mail] presented the following explanation :

I tested that idea around 20 years ago :-)

I gave the idea up simply because our water pressure was not sufficient to provide a jet of water quickly enough on the opening of the solenoid.

One solution to the shock, might be to T in a length of hose pipe between solenoid and water supply. If the new length of pipe were maintained full of air, then because the air is and the hose are compressible, it would act as a buffer to the shock.

[Davey]

That is a perfectly sound idea, used in industry as well as some domestic situations. I have seen it in a basement at the utility sink. I once had the same problem with a four-inch water supply pipe, which descended vertically from a plant ceiling for more than 40 feet before meeting a solenoid valve. The resulting shock made the pipe's horizontal run, before the change to the vertical, move a foot sideways at its worst. We tried these shock absorbers, but they weren't man enough for this job. It was fixed by installing a slow stepping valve, at the top of the vertical drop, which was slow enough to gradually control the water flowrate. Getting up to the valve was an experience in itself.

[Grimly Curmudgeon]

problem - either by:-

making it open instantly.

Insert a T-piece with a blanked vertical pipe from it of around a foot length of 1" pipe. Leave it filled with air. It will act as a shock absorber.

[fred]

In article , [e-mail] writes

If, as you say, the shock is causing a leak in your domestic supply pipework (not your hose or hose fittings) then your pipework or that of your supplier is faulty. Solution, fix it, or have them fix theirs.

If you are talking about the shock affecting the hose fittings then the following may help:

By nature, solenoids are bangy, they operate with more and more force as they close so it is an inherent problem. You can get slow close solenoid operated valves for irrigation but they are a bit slow in operation so I doubt they would be suitable.

You can get shock arrestor capsules (similar to expansion vessels) for use on water systems. See water hammer arrester half way down this page:

inverted pipe idea wont work long term as the air will be re-absorbed by water under pressure.

[meow2222]

e water sprinklers. This is controlled by a PIR which activates a 12v sole= noid valve connected to the garden hose that then connects to the sprinkler= .

taneously. This sends a shock wave back through the water system. And the r= esult was that the shock waves caused a water leak at a junction of the inc= oming water supply from the street.

ave problem - either by:-

l making it open instantly.

Oil the solenoid. Try 20/50 first.

NT

[harry]

e water sprinklers. This is controlled by a PIR which =A0activates a 12v so= lenoid valve connected to the garden hose that then connects to the sprinkl= er.

antaneously. This sends a shock wave back through the water system. And the= result was that the shock waves caused a water leak at a junction of the i= ncoming water supply from the street.

ave problem - either by:-

ill making it open instantly.

[Doctor Drivel]

Until the air dissolves.

[Onetap]

You can get slow-closing solenoid valve for this application.

You could also use a solenoid valvle as a pilot valve operating a diaphragm valve, with a restriction in the diaphragm discharge; I can't recall how that's done now. Many large 'solenoid' valves are pilot operated diaphragm valves.

Plan B, get a motorized ball valve; less likely the stick open than a solenoid.

[Doctor Drivel]

Make sure it can handle the pressure.

[Andy Dingley]

taneously. This sends a shock wave back through the water system. And the r= esult was that the shock waves caused a water leak at a junction of the inc= oming water supply from the street.

If that did it, it was knackered anyway,

If water hammer is a problem, fit an arrester. This is a vertical length o= f pipe (ideally fat pipe), capped at the top. It fills with an elastic air = bubble inside it.

[Grimly Curmudgeon]

So put a Schraeder valve on top.

[Doctor Drivel]

Oh my God, he wants to pump it up every few weeks.

[Grimly Curmudgeon]

Well, you have to do something to while away the idle hours. You could draw on your experience with pump-up penile insertions.

[Doctor Drivel]

How does your work?

[Grimly Curmudgeon]

And again, in Engilsh?