replacing a stop tap (without getting wet)

[Jennie]

Hi all,
Just a theoretical question...
A while ago I changed the head gear of a stop tap. I was told a bit of water might come out of the opened valve - it came gushing out. Luckily I had a bucket underneath, and the new bit in my hand - I whipped the new tap in super fast. I was surprised by how much water was still in the pipes (below the kitchen tap, which was my lowest drain point as there was no drain valve on the lower pipework). I've since calculated that 1m of 15mm pipe holds 0.7 litres of water.
I've been pondering how I might approach this next time - especially if the customer has nice flooring.
One solution could be to cut into the pipe (either just above the stopcock, or under the kitchen sink) with one of these: DRAIN COCK SELF CUTTING LOCKSHIELD RADIATOR VALVE EXTENSION PUSH FIT | eBay
I could drain the water out, sort the stop tap out, and then replace the temporary drain valve with a soldered tee/end-feed drain valve.
What do you reckon?
Thanks for all your advice,
Jennie

 

[Ermintrude]

Wet vac chuck!

 

[Jennie]

Oh. Interesting. Maybe I should buy a wet vac (they sound extremely useful).
I take it I'd just shove the nozel into the open tap valve and let it suck?

 

[Ermintrude]

Yep, or as u crack nut switch it on and catch every drop

 

[gassafe]

I carry old towels on the van... Perfect for this type of job!!

Too much hassle bringing in the wet vac all the time...

 

[Alex Pelton]

got one of these. several of the guys i know have one and they take some serious abuse. useful for clear blockages getting rid of water in pipes while soldering. emptying rads etc etc a plumbing essential

Wet & Dry Vacuum & Blower - Workshop Tools - Power Tools -Tools, Electrical & Plumbing - Wickes

 

[tamz]

I've since calculated that 1m of 15mm pipe holds 0.7 litres of water.

0.1369 litres Jennie

 

[Alex Pelton]

calculating the volume of one meter of pipe


crosssectional area of pipe x length


3.142x15squared x 1000


3.142 x 225 x 1000


706950 cubic millimeters = 0.7 litres

 

[Jennie]

Oops. I thought 0.7 was a lot. It turns out I forgot to halve the 15mm diameter to get the radius in my calculations.

 

[Ermintrude]

It's Pir^2 or Pi (d^2)/4

So 0.0075^2 * 3.14 = 0.00017m3

Or 0.17l

 

[tamz]

πr2h 15mm pipe 0.9mm wall ID =13.2mm 3.142 x 0.0066 x 0.0066 x 1 =0.000136865m3 1000 litre/m3 so x the answer by 1000 = 0.1369 litres (i'd written m2 instead of m3. Why isn't this thing leaving spaces between lines)

 

[tamz]

I like numbers Simon :lol:

To answer the question. I'd throw an old rag down to catch the water. It is nothing.

 

[Mike Jackson]

If the original one had been fitted to regs it would have a drain off just above it.

I chuck a few old towels down to catch the water. If I think there's going to be a lot I use a black sack.

 

[tomplumb83]

Just work quicker!!!
..... and take a towel with you.