dodgy plumbing

[gucciman]

i need to call out a plumber to look at our hot water but would like an idea of whats going on first so i dont get totally ripped off.

our hot water in the bathroom runs off our baxi bermuda back boiler, with a cylinder in the bedroom upstairs and presumably a header tank in the loft (haven't been up there to look yet)

when we run a bath of hot water, if were not careful and dont turn the tap off before the water runs out then we seem to get an airlock which means we cannot get anymore hot water out.

the missus has a trick where she connects a length of hose from the cold tap to the hot and blasts cold water up the hot tap (for a couple of minutes), this sometimes then gets the hot water running again.

anyone know what the problem could be?

my dads a gasfitter and he reckons it may be something to do with the header tank being too small or faulty, but he hasn't seen it to check as he lives 140 miles away and hasn't been down yet.

[stanleyman]

Air is being drawn down the cylinder vent pipe which is connected to the hot water outlet. This usually happens if the feed tank is not high enough above the cylinder or the vent pipe is too small, 15 mm rather than 22 mm.

The water level in the vent pipe is level with the tank level until you open a tap. As this is the easiest route for the water to the tap the water level in the pipe is able to fall quicker than the tank level and this is proportional to the flowrate. Filling the bath slowly will help.

The air drawn in then gets trapped in the pipes and stops the flow as the head of the tank is insufficient to push it through. Many systems draw air and hot tap spluttering is a sure sign.

You can cure this yourself quite easily by fitting a non return valve in the vent pipe just above the water level at the feed tank. This allows air up, so fit it the right way round, but won't allow air down. You need a gravity check valve for best results, these have a weak spring.

[pilotlight]

gucciman, Your gasfitter dad is probably correct ( tank too small ), or the water pressure to the tank is insufficient to fill the tank quickly enough to compensate for the amount of water being drawn off.

I would not recommend the fitting of any valve to the open vent / expansion pipe.

Hope this helps.

[gucciman]

ooops, 2 conflicting answers, now what do i do!

are either of you qualified plumbers? pilotlight suggests your a gas fitter like my father.

probably best if i ask the old man reall really nicely to bring his tool kit with him when he finally comes down to visit.

[stanleyman]

The tank has already been mentioned as possibly being too small or having insufficient supply which I agree with but it would have to be quite small and also have a very poor water supply. Has he suggested checking all the valves are fully open?

In my experience it can be the case that a tank fitted is too small for reasons of access or room but any plumber worth his salt would fit two tanks to give sufficient volume to at least equal the cylinder regardless of water supply. It isn't difficult to work out, however, I have to concede that most plumbers and heating engineers, certainly the ones I've employed, find it difficult to actually design a system and stick to one tried layout regardless because they have always done it that way and cannot grasp new and better ways of doing things.

What I have found more common is either the cylinder mounted too high and/or the tank fitted too low giving a short vent pipe with the effects I have already described.

I don't see why pilotlight should object to a full bore oneway valve in the vent, I've never had a problem, I wouldn't recommend it for a solid fuel installation where there is the possibilty of frequent cylinder boiling but properly fitted it is as safe as an unvented cylinder, bearing in mind it is also open for expansion via the cold feed, new immersion heaters have a limitstat and most cylinders have a thermostat. Where is the problem?

[gucciman]

i really dont know the first thing about plumbing or any diy for that matter. i read the answers out to my old man and his first comment was that you do not put a valve in the vent pipe, he said something about the valve would only open under pump pressure or something like that.

he maintains the problem is probably due to the header tank not supplying the cylinder quickly enough, he said the ball valve could be stuck, a valve in the feed pipe may not be fully open, or some sludge could be obstructing the pipe.

i will get him to look at it when he comes to visit. unfortunately though our trick of blasting the cold water up the hot tap hasn't worked this time for some reason, we have had no hot water for 3 days now.

[pilotlight]

gucciman, Sorry for the delay (everyone needs a break now and again ). It's inevitable that there will be conflicting answers to questions posted here. It's quite possible that more than one answer could be correct, or help you with the problem. I wouldn't dream of answering a question did I not consider myself qualified enough to do so ( I'm sure the same will apply to others ).

( stanleyman, see www.iphe.org.uk/databyte/tank_cistern_installation.pdf section on open vent pipe )

Good luck.

[stanleyman]

Blank page I'm afraid, what was it about?

[pilotlight]

Open vent pipe "It should be no less than 19mm. and have no valve fitted to it."

Good Luck.

[stanleyman]

I can't see what you've refered to but I can of course see why a shut off valve wouldn't be fitted but a large bore oneway valve? You haven't told me why this valve can't be fitted and have you thought about whether you actually need a vent pipe from a tank fed cylinder these days, provided it is protected like an unvented cylinder of course? Limescale in the cylinder outlet can also cause a problem like this.

[pilotlight]

stanleyman, Longer back than I care to remember, I was taught that it was dangerous, and a contravention of codes of practice to fit a valve of any kind onto a open vent pipe. The reason being that the open vent is a natural safety outlet, as any mechanical / electric valve, or other safety device can fail. I presume that this is the reason the Institute of Plumbing and Heating Engineering forbid it.

Institute of Plumbing and Heating Engineering can be contacted at [email protected] for confirmation.

No posting as yet from gucciman to inform us what the problem turned out to be.

Good luck.

[stanleyman]

I know what you are saying but my point is, many things have changed and improved in the past decade or so and what may have been considered dangerous years ago with usually uncontrollable boilers is now not the case with gas, oil or electricity. Where is the vent on an unvented water heater or cylinder or sealed system? It's got a valve! The old regulations don't always keep up with new developments.

I've been involved in lots of experimental work and you do need to turn things on their head and ignore restrictive and unneccessary regulations to get the improvements. If you didn't we wouldn't have all these better systems!

Anyway, we've taken up enough of gucciman's question, apologises to you and I hope you get it sorted soon.

[gucciman]

stop arguing you guys!

im still waiting on my old man to pay us a visit to get the problem sorted but in the meantime the old squeeze your palm over the kitchen sink mixer tap trick got the water running again.

while your both around, i posted before that i wanted to retrain to be a plumber or gas fitter after i was made redundant on xmas eve. well its proving impossible. i just cant get any training from the job centre, the ambition energy scheme only takes 16 a yr on in my area and they have thousands apply, you have to have been on the dole for 12 months minimum and they dont like well educated people for some reason. i cant get an apprenticeship because im 36 and ive been told by the careers centre that if i go to college off my own back and study plumbing or gasfitting i wont get a job at the end of it because i wont have any practical experience. looks like i will have to forget the idea.

[stanleyman]

Sorry didn't see your later reply until today. Hope you've got things sorted now. Sorry to hear of your redundancy. If you want to get into plumbing and heating then get your own training but don't take any notice of anyone saying you won't get a job, how do they know? You do need to have a practical side for this.

You can always work for yourself as I do and I've never had any formal training in it, just taught myself and had experience with heating controls which helped. I really started fifteen years ago when I couldn't get anyone knowledgable enough to install the Stanley range cookers I was selling so I did it myself.

The pipe fitting was easy enough and then I started designing systems for them which simplified the installation and improved the performance (they had problems when installed conventionally). I manufactured thermal stores and mains hotwater systems well before the main manufacturers caught up.

You can't always rely on someone else for your income and the old saying "if you want a job done properly do it yourself" is worth remembering. The best of luck in your new career whatever it is.

[pilotlight]

gucciman, Apologies from me also for the delay.

As I'm sure Stanleyman would concur, there was no argument. There are so many written, and unwritten rules in the plumbing/ heating/gasfitting industry that there are bound to be differences of opinion regarding a certain issue.This even applies to the " experts " who teach, or write about heating etc.

Sorry to hear of your predicament. If this is the type of work you really want to do, I'm sure you will find success somewhere.

Cheers gucciman, --- and stanleyman !

[gucciman]

thanks a million gents

the old man finally got chance to come down and service all the gas applicances for us yesterday. water problem was a dodgy ball valve which was re-filling the tank too slowly, tank was the right size.

while he was here he serviced our baxi bermuda back boiler and fire, burner in the fire had to be replaced as it was cracked. he also serviced our cooker, the mans a diamond.