Help! Am pulling my hair out....biting nails......NPT/BSP threads
Turbo Mini Forums

I have acquired this plumbing fitting from USA so it has 3/4 inch NPT male and female threads. It is used to arrest water hammer caused by rapidly shutting washing machine valves. One end connects to the water inlet the other connects to the washing machine. I can attach the female end without problem as the male end of a 3/4 inch BSP fitting screws on without undue force. The male end is another story. About one and half turn and I encounter high resistance. My dilemma is, "should I use major force?"
When correctly fitted, there will be a rubber seal to prevent any leakage.

Is there anything I can do to avoid any damage? Lubricant?....anything.

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Wouldnt use excessive force...

But wow what a first post! Lol

Thanks.

forgive my plumbing ignorance, but Im quite sure you can just use a vertical section of capped pipe T'd into the feed to stop water hammering, as the air which cant bleed out in the vertical section acts as a shock absorber. save you ordering more bits from the US of A

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

http://www.toolstation.com/shop/Plumbing/d...i+Rester/p64117

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Thank you Dennis. Your suggestion does indeed work. Disadvantage is that after a while the air gets absorbed, the tube gets filled with water and the hammer returns . You then have to drain the water. My purchase was meant to be installed in 10 minutes was guaranteed for life.

Thank you oli79. That link basically is the same device, made by the same manufacturer and I would guess has the same NPT threads.

Ok, well in your first post you state they are npt threads, which by their very nature are tapered. I cant comment of what threads they use in the usa but in the uk, washing machine valves are a 3/4 bsp paralell thread and all accessories seal on the flat face with a washer.

The one in the link,having fitted dozens of them, is definitely 3/4 bspp, parallel thread. The female end screws onto the washer valve sealing with a 3/4 rubber washer and the machines fill hose screws directly onto the male end and again seals on the face with its own washer.

From the picture is seems as though your trying to attach a 3/4 x 15mm compression tap connector to the outlet side for some reason. Its most likely it wont fit because the flanged end of the tap connector is too large to go inside the fitting on the rester, because as i said above the rester outlet is a face sealing union.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

To elaborate Dennis, in the bottom of the rester is a small piston sealed with o rings that separates the water and air cushion, on larger units a rubber diaphram is used much like and expansion vessel. Its not done for air absorption only, there's a regulation somewhere that doesn't allow you to have dead legs of pipework on potable water to prevent the formation of legionella.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Thank you oli. I actually have the minirester from toolstation installed, as per the picture attached here, but it does not work, The picture shows the minirester from toolstation connected to a washing machine hose. The new design has a better chance of capturing the shock as the incoming water is in line with the piston These are not available as yet in UK. I am assuming that the miniresters sold in UK have the same threads (NPT) as those sold in the states. I have asked the manufacturer and their agent in UK but they are not answering! PS cant seem to attach a picture. I will keep trying.

Thanks oli. Worked out how to attach picture, so here it is .
Thank you oli. I actually have the minirester from toolstation installed, as per the picture attached here, but it does not work, The picture shows the minirester from toolstation connected to a washing machine hose. The new design has a better chance of capturing the shock as the incoming water is in line with the piston These are not available as yet in UK. I am assuming that the miniresters sold in UK have the same threads (NPT) as those sold in the states. I have asked the manufacturer and their agent in UK but they are not answering! PS cant seem to attach a picture. I will keep trying.

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I know less than nothing about plumbing so appreciate the replies!

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Dunno then, these things are difficult to diagnose other than in person so the best i can give is conjecture, personally i doubt changing the orientation if the bulb is going to solve your problem.

it looks like you have it threaded into a pressure reducing valve of some description, if not i was going to suggest if you have very high static water pressure to put one on the incoming main set at 3bar.

Other things to look at are- it might not be water hammer more a large length of bare unsecured pipe under a floor which physically knocks with the shock, you could also try the much larger diaphram type available at a good plumbers merchant's. You could also try a check valve before the rester to limit the volume of water which can shock back.

Other than that, buy ear defenders, use a laundrette, move house or buy a wig for when you've torn ball your hair out

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Thanks oli for your help. There is undoubtedly a length of unsecured pipe inaccessible under the floor. Until recently, I had a low pressure hot as well as cold system fed from a cistern high up in the roof apex. I changed to a mains pressure system whence the problem manifested itself. I could move the pressure reducing valve upstream, progressively reducing the pressure until problem goes away. Think that's what I will do. I have the valve. Its simply a question of removing it and installing further upstream.

Whats worth a try is putting full bore service valve ( or gate valve) near the appliance thats creating the water hammer, then close the valve bit by bit until the resination stops or lift your boards and secure the pipe properly.