Query about cold water storage tank ball valve replacement

[smithers0106]

Hi,

The ball valve is slightly leaking in the loft CWST, so the overflow eventually starts dripping if we are not using the bathroom taps or flushing the loo.

I'm comfortable enough with the concept of replacing it, but just want to confirm about sizing and the existing valve's connection. Firstly, I assume that when referring to 1/2in or 3/4in valves, this is referring to the diameter of the threaded part of the valve, which connects to the mains water pipe? I have measured the threaded part of the existing valve as being 20mm which, taking account of slight inaccuracy looks like 3/4inch to me.

It seems that 3/4in Part 2 valves are pretty rare (at least searching online anyway). I had looked at part 1, which appears to be what is on my CWST now, until I did some reading and realised it should be a part 2. As our house is from the 70's, I assume the regulations were different then.

The main point about the existing connection is that the replacements I looked at in B&Q (which were 1/2in, but I was just checking the fitting procedure) say to fit a tap connector to the existing mains pipework, then connect the new valve. But, on checking my existing valve, it looks like there is a copper tap connector soldered onto the pipe, which is taking the 15mm mains and changing it to (presumably) 3/4inch to fit the valve onto (I guess this is the old fashioned way to do this?)

Is it just going to be a case here of buying a 3/4in part 2 valve and ball, some fibre washers, then fit it onto that existing copper tap connector?

Oh, the CWST, although it's plastic, has a bunch of brown stuff in the bottom of the tank (looks to me like some copper deposits - is that possible?) I'm not quite clear, given the valve is 3/4in (presumably 'old fashioned' size) and the brown stuff in the tank, if it's just worth getting a plumber in to replace both (and presumably fit a 1/2in part 2 instead in the process?)

Sorry for the ramble, hope someone can clarify the above for me.

Thanks,
Andy

Untitled

• smithers0106
• 31 Jan 2010
• 1

Untitled

• smithers0106
• 31 Jan 2010
• 1

Untitled

• smithers0106
• 31 Jan 2010
• 1

Untitled

• smithers0106
• 31 Jan 2010
• 1

 

[Richard C]

Have you checked/replaced the rubber sealing washer? You may not need to replace the ball valve or even remove it; also check that the ball float hasn’t sprung a leak, it may be full of water.

 

[dextrous]

Plastic tank is fine if it's not leaking - the brown deposits are nothing to worry about and perfectly natural (partly settled sediment from incoming water supply). Chances are the ballcock is 1/2" - a photo would help tremendously here.

 

[powell30]

If it's the ball valve leaking ie won't shut off you couls trip and replace the innards only but it is much easier to fit a new one. If sure if you buy a 3/4 it will fit the nut already there......remember your washer too

 

[TicklyT]

Are you aware that a 1/2" pipe thread is in fact about 3/4" diameter, and a 3/4" pipe thread is about 1" diameter?

The nominal size of the thread refers to the size of the bore through the middle of an iron pipe the thread would have been on the outside of.

If you measured the thread as about 20mm, that sounds like 1/2" BSP, so you just need to isolate the water supply, unscrew the existing tap connector from the old valve, and fit a new 1/2" valve.

Get yourself a new fibre washer for the tap connector. You may not actually need it, but sodd's law says the old washer won't seal on the new valve unless you have a new washer available.

If there isn't one already, now might be a good time to consider fitting a service valve in the cold feed to make future maintenance easier.

Set your new valve to cut off when the water is a couple of inches or so below the overflow. That allows for expansion when hot water is heated.

The brown stuff in the bottom of the tank is probably a mixture of odd grains of sand or grit that get carried along the water mains by the flow, bits of rust (iron oxide) from the mains themselves, airborne dust particles and bits of loft insulation that have settled in the tank over the years. All pretty much inert and harmless stuff.

Best to remove any drowned rats or pigeons though

You can get slime like growths in tanks of stagnant water, sometimes that happens to heating feed and expansion tanks, as there's no flow through them. That would be very unusual in a cold water storage tank, as the water usage ensures regular changes of the water in the tank.

 

[smithers0106]

Pics uploaded to the original post (inc one of the 'brown matter' in the bottom of the cwst! and one with tape measure to - hopefully - show size)

Thanks for all the really quick and detailed advice, I appreciate it

In answer to comments;

I tried an in-place repair but the cap on the valve would not budge at all, even with WD40. Given the general look of it (not sure when installed, but looks pretty old to me) I'd rather fit a new one anyway.

TicklyT - was not aware of the thread sizing - hence I thought better to ask about it on here. What you say makes sense; I didn't want to get as far as buying a 1/2in part2 then find it was wrong only AFTER removing the old one!

So does the valve look like it's really a 1/2in after all? - sorry, I could not get the tape measure perfectly in few as I was crouching precariously on the joists at the time

Thanks again all,
Andy

 

[dextrous]

Yep - standard 1/2".

 

[smithers0106]

Yep - standard 1/2".

That's great, thanks for confirming it. Off to B&Q tomorrow, methinks!

 

[anotherbgeng]

yep standard 1/2'' ball valve ,,,if i remember correctly B +Q do a ball valve service kit which contains everything to overhaul the ball valve,,,

 

[Nige F]

Get a new part 2 ballvalve half inch . The thing comes apart @ that big nut near the wall of the cistern. Have a play with the new one and you`ll soon see how simple it is Definitely needs a part 2- that overflow is too high, the inlet could dip in the water as it is.

 

[smithers0106]

Hi, just a quick update as I hate it when folk ask for help then you never
hear back how they got on

part 2 1/2in High pressure valve and ball successfully fitted today, washers and tape used
for good measure. Leak free, so far

thanks for all the help gents, I would have been ordering a
3/4in valve online were it not for your advice

oh and it was easier than expected, so that was great.

 

[stoutlad]

Hello, I have come across this post in a search on Google. I am in a similar position here but not sure if it needs replacing. The local water authority had recently turned the water off in the area to do work and when it has come back on the pressure is far stronger than it was previously, the force is incredible. A few people here have said that their CWST overflow is now dripping when the water is not used for a few hours.
Do you think this needs replacing or can there be another reason for this that has something to do with the force of the water coming in? It seems strange that so many people have had this problem since the water has come back on

 

[TonyW2]

If the incoming supply pressure has increased, the ball valve position requires lowering to maintain the level at which the supply is cut off.
Bend the arm downwards, carefully.
Strip, clean and replace the washer if you have time, as it could be that the drip has been caused by dislodged rubbish rather than pressure change alone.

Best to start your own threads in future

 

[stoutlad]

If the incoming supply pressure has increased, the ball valve position requires lowering to maintain the level at which the supply is cut off.
Bend the arm downwards, carefully.
Strip, clean and replace the washer if you have time, as it could be that the drip has been caused by dislodged rubbish rather than pressure change alone.

Best to start your own threads in future

Thanks, I'll give that a go