Water Tank and Expansion Vessel Overflow?

paperclap

Hi all,

In the middle of having my roof, fascia, soffit and guttering done.

In our loft, we’ve a water tank and an expansion vessel.

The water tank has a 22mm copper pipe coming out of the water tank. But, leads straight into the soffit (inside! Not outside!). It appears it used to go out through the fascia, as the previous owner has clearly cut the pipe back and filled in the hole with silicone. The question is, why? As far as I’m aware, the water tank is still in use, as we have a gravity fed low pressure shower and bath (taps). And, pretty sure I can hear it filling up (when I’m up in the loft), after we’ve flushed the toilet. Or, am I confused things and this water tank is redundant?

The expansion vessel has a 15mm pipe coming out of the pressure setting fitting. Then, into a 15 to 22mm fitting. Then a 22mm copper pipe. This copper pipe leads straight through the fascia, as you would expect.

What I was hoping to do is replace with typical 21.5mm PVC overflow pipes to suit the new white fascia.

Photos attached to save confusion!

Thanks.

grumbler

laurencewhymark said:

The water tank has a 22mm copper pipe coming out of the water tank. But, leads straight into the soffit (inside! Not outside!). It appears it used to go out through the fascia, as the previous owner has clearly cut the pipe back and filled in the hole with silicone. The question is, why? As far as I’m aware, the water tank is still in use, as we have a gravity fed low pressure shower and bath (taps). And, pretty sure I can hear it filling up (when I’m up in the loft), after we’ve flushed the toilet. Or, am I confused things and this water tank is redundant?

Well, only can find out. Just open it and look inside. And there have to be two other pipes connected to it - 15mm mains pipe with an isolator valve (top part of the tank) and bigger diameter pipe at the bottom part.

Usually you cannot use 'low pressure shower' as a real shower. For gravity systems it's typically either electric shower connected to hight pressure mains or a power shower with a pump.

The expansion vessel has a 15mm pipe coming out of the pressure setting fitting. Then, into a 15 to 22mm fitting. Then a 22mm copper pipe. This copper pipe leads straight through the fascia, as you would expect.

What I was hoping to do is replace with typical 21.5mm PVC overflow pipes to suit the new white fascia.

Looks usual and yes, typically it's a plastic pipe. But it's not 'pressure setting'. It's for topping up the system automatically when water evaporates.

plumb1_2

It’s not a pressure vessel, it’s a prv and looks like it’s coming off a T, can you change to normal overflow pipe? Depends if it’s coming off a hot or cold pipe.

paperclap

Thanks both.

Well, I’ve just been quoted £100-£150+VAT to do this job… so now even more determined to do it myself, given the materials are about £30 or less!

While I did plumb new pipework and radiators into our house, I’m no plumber.

Is this job a “simple” case of literally disconnecting the pipework and fitting new stuff?

No drainage of any water systems needed, I can’t imagine?

Bendy_House

laurencewhymark said:

This is a PRV, Plumb1_2? Isn't that a weird place to have one?! Reckon it was put there as the mains supply to the ballcock was making it vibrate?

And what's with having a 15mm-sized pipe on the overflow?! Surely that will seriously reduce its capacity should the ballcock stick open, or other fault occur? Unless the PRV has been set so low that the F&E tank can only fill up slowly, even if the ballcock does keep filling?

Blimey - confusing.

LwM, yes this is DIYable, and we can guide you through it. There's very little that can go wrong - ie little risk - and it will be tested afterwards to make sure the overflow will cope.

BUT, you really need to know what you are starting with - and that's to have a gander inside both these tanks. Let's face it, if you cannot get to look inside it, you certainly ain't going to be able to fit anything to it...

Really, each tank needs to have its own overflow pipe running all the way outside, with their ends protruding enough to (a) not pour down the wall or cause any other potential damage to the house fabric, and (b) be unmissable should it be overflowing - ie you want to see and/or hear that flow when it happens (as surely, one day, it will).

Controversial point - would anyone here consider joining the two overflows at the eaves so there's only a single outlet passing through the soffit, the one that's already going through? I mean, what are the chances of BOTH tanks overflowing at the same time :-)

Bendy_House

Oh, and the overflow pipes are easier done in rigid plastic and solvent fittings.

paperclap

Water tank
Definitely in use. Has water in it!

Expansion vessel
Not sure what a PRV is, but almost certain this is an expansion vessel, as it says “expansion” on the side, but in French I think. Plus when Googled, it is literally the same thing.

The expansion vessel has 15mm, but does expand into 22mm very shortly after

Yes, that is what I was thinking - PVC and solvent cement.

But, what fitting would exit the water tank to make it compatible to a 21.5mm overflow pipe? Alternatively, leave a slither of the existing 22mm copper in place with the compression fitting (or whatever it is), and get a 22mm to 21.5mm fitting, then overflow pipe?

As for the expansion vessel, would it be easier to leave the existing 15mm copper pipe in place (as it’s all soldered up), and simply get a 15mm to 21.5mm push fitting, then fit new PVC pipe?

Also with regards to making this somewhat of a neat job, would it be best to try and veer these toward the side of the rafters, so they can be clipped t the rafters… rather than in their current floating state?!

plumb1_2

The valve in the picture is a prv not a expansion vessel. You need to find out why it’s there.

Buy a solvent weld tank connector 21.5 then just pipe from it.
Plus why was a tradesman time getting a quote for it, when 100% you are going to Diy it.

paperclap

Think there’s some confusion here. You may very well be right in that the valve is a PRV. But, I’m referring to the tank it is connected to - the (red) tank, which is just out of sight. It looks like this photo. 

Well, I wasn’t 100% DIYing it. I’ve never had to do this before, so wasn’t sure if it was something a DIY should do… so hence why I wanted to get a few quotes first, before delving in

Bendy_House

Tee-hee - cross misunderstandings!

LwM, the actual TANK is an expansion tank. Usually referred to as an F&E tank - 'Feed & Expansion' (I think). Ie, it feeds the CH system, and also allows the hot, expanded, water somewhere to go.

Plumb is referring to that weird red-topped valve near the ballcock inlet. He says it's a PRV - a Pressure Release Valve, I'm guessing - whereas I originally thought in my reply above it was a PRV - a Pressure Reducing Valve. Hey-ho...

Either way, it's just weird, man. I cannot think of any good reason why it should be there. Or any bad reason either.

Anyhoo, if changing to plastic - which makes sense if you need to redo it - then you are best to start afresh with suitable tank connectors for this - it's a pass-through-and-screw-down-the-collar job. I agree - floating pipes are just asking for trouble - one biff and there's the potential for leaks or even splitting the tank, say if it's really cold up there. So, yes, plan it all out, buy some 90 and 45o elbows, and clips...

I'd lose all the 15mm on the overflow - it just ain't good enough :-)

plumb1_2

With the ev (not pictured) and a prv maybe the heating system has been altered to mains pressure and no need for the expansion tank?

Adding little bits of information is like a guessing game. So I’ll end my input.