Virtually no flow at bath ( longish)

[9100DN OWNER]

Small cottage, single story, vented direct hot water system and wood stove with back boiler.

Friend reports that prior to this week

Bathroom wash hand basin hot tap was working well, kitchen hot tap OK, but bath hot tap tended to "Air Lock" so bath not used for three years as Electric Shower available and after the bath taps were used it needed the owner to connect the wash hand basin taps together with a hose to get any hot taps working again.

Back boiler in stove springs leak it is carbon steel and connected to the

120 litre direct, vented hot water tank. I volunteered to replace boiler that was Thursday morning.

Boiler replaced in stove. Water turned on. Hot tank fills no problem. Goes up to loft to see how storage tank is getting on. Finds it is 30 year old, galvanised and is very rusty. I'm not happy but it fills up.

Without heating the hot water, tests tap. Very very low flow. Connects washing machine pipes together as advised here. Puts thumb on vent pipe after letting it flow for a while and water starts to come up outlet of storage tank. So assume no large blockages.

One thing after then turning of the washing machine link and waiting a few moments there is the sound of what appear to be air in the system moving about!!

Now test hot water taps again. Wash hand basin about Ok but not as good as before boiler replacement! Kitchen tap not wonderful but it is a mixer tap and may not be suitable for a gravity system. Bath tap flow very poor. So go into loft and the bath tap appears to start by draining the overflow pipe and it appears there is not enough water rising from the hot tank below to keep it running.

Cold storage tank in loft with it's outlet some 600mm above the level of the loft floor. The outlet pipe drops to the loft floor, runs two metres horizontal and then drops through ceiling, then 1.5 metres drop to the bottom of the hot water tank. There are two pipe bends and a stop valve and two tees in the run one for the boiler and a final one for a drain. Remove stop valve it is opening fully with a small amount of gunge. Clean and replace in system

From the top of the hot water tank the pipe work goes horizontal say 400mm,

90 elbow and rises say 500mm then through ceiling. ( That 90 elbow between the horizontal and vertical pipe had gunge in it now cleaned but I'm scared to remove top connection from cylinder as I may rip the top of the tank it is ten years old.), then runs some 10 metres horizontal. then down through ceiling two metres to the bath. On the way it goes through 3 off 90 elbows, two 90 bends, a tee for the overflow and then gets to the bath. All these pipes are 22mm.

Can anyone advise if this run is just too long and complicated for a gravity system to run properly. I realise that a nasty old storage tank and steel boiler are not helping either.

I have just ordered a few plastic storage tanks as the loft opening is tiny and the storage tank needs replacing.

[John Stumbles]

...

how do you know this?

Is there much difference in behaviour if you almost close the valve in the pipework feeding cold water to the bottom of the cylinder?

Is it a hard water area?

Could it be that the top outlet of the hot water cylinder is scaled up and letting little water through? That could explain the vent pipe draining and air consequently being drawn into the system. Also, since it's about the one part of the system you haven't opened up to check, Sod's law dictates that that's the culprit :-)

Can you cut the pipework (assuming it's copper not steel) close to the cylinder connector and investigate?

[9100DN OWNER]

The friend is a lady and she said so!!! for drop in performance recently. Otherwisw this is from getting friend to open the hot water bath tap when I am standing beside the cold water storage tank.

I will try that tommorrow. I know it stops the cylinder filling when closed.

No, very soft water area, Aberdeenshire

When I last filled the system with the hot water cylinder say 10% full, I turned on the washing machine link and the water was comming in there at what appeared to be with some force.

Never though of that!

Eddie

[John Stumbles]

Sorry, I meant how do you know the bit about draining the overflow pipe (since you can't see into it)?

I've seen an almost-blocked outlet from a cold water tank in a soft water area (mid-wales, Elan Valleys supply, so I supose it must have been reactions between different metals rather than anything in the water itself). I wonder if the same could happen at the hot water cylinder outlet?

Though with mains behind it you'd expect some force, even if the actual flow wasn't up to much.

[BigWallop]

The part about the pipework coming from the loft to a downstairs hot water storage tank, then rising back up through the ceiling to the loft before coming back down to the bath, is the bit I don't get. The pipework will fill with water alright, but it has lost all momentum in doing this dance all around the house. You're only left with a pressure head height from the last bend in the pipe down to the bath tap. I think this could be your problem.

You say that the hot water vent pipe (overflow you're calling it) is also on this part of the pipework, and that it drops its water level when the bath tap is turned on. I'm not surprised by this because the head of water above the bath tap will be the height of the water in the vent pipe, which should become level with the water in the cold water storage tank. The pipework then does this dance all over the place and will take ages to fill up again, especially if the bath tap is still turned on.

Is there room in the loft for a hot water cylinder? Even if it lies on its side? Lifting the hot tank in to the loft and dropping all the pipework down from there will cure all your ills in this plumbing system.

[9100DN OWNER]

Agreed

This was put in 30 years ago and it was a solution based on use of space and you can't go wrong with a solid fuel back boiler if the electricity goes off. It does here in the winter quite often. It was not based on the dynamics of a gravity system.

Max size of loft opening is 400mm and the useable height to the highest point is less then 1.5 metres. Friend still wants to use back boiler in wood stove. So need say 1 metre head above hot tank for it to work properly so little chance of that!

Further she has to run off boiling water quite often as the water cannot be used for a bath or shower, it is a one person household so no real use of water as the bath taps do not work and she is a shower type person so uses an electric shower!!!

My suggestion is to move the cold water storage tank above the bathroom and the hot water cylinder to an airing cupboard next to the bath room. This means no return trip to the loft for the hot water and to take the boiler out the stove and replace it with a fire brick. I was rebuffed as it would be loosing the advantage of the back boiler!!!!!!!!!!

So that was Thursday, Friday and Sunday lost but who wants the time off!

Eddie

[9100DN OWNER]

Basically hearing it.by standing beside the cold water storage

I will try your suggestion of trying to cut this pipe near the joint at the top of the cylinder and pushing a wire in to clear any possible blockage.

[BigWallop]

That all sounds like a good method to cure it, but you can still keep the back boiler in place. I loved our old coal fired back boiler, and 'am sorry we took it out now. I could have fitted a pump to the back boiler and used an indirect cylinder to heat the water for our system, but I jumped in to quick with one of these modern gas things that hang on the wall. :-)

You still have all the options open to make a bad job good here, so think about what layout you'd need to heat the hot water tank from the back boiler, and still keep the pressure to all the taps at an acceptable level by re-arranging the pipework to suit.

A hot water cylinder doesn't have to stand upright if you seal all the un-used holes. A cylinder lying on its side in the loft, with a coil inside (indirect cylinder they're called) to heat the water from the back boiler, will do the same job of supplying hot water well enough, and it doesn't need to be too big. It also create space in its old postion for other things like a new storage cupboard.

As long as you can get rid of the part of the system that rises above the height of the bathroom floor, then you've got the job cracked.

LOL !!! Yeah !!! Who needs rest and relaxation. We're hard men !!!! :-)