Sporadic hot water - Only some fittings getting hot water

[plumberdan]

Question to picasso- are you a registered unvented cylinder installer(no disrespect intended here) that pump is yes the wrong type, and in the wrong place altogether! Isolate it using the pump valves! There is a risk of legionnaires disease here! I would still get a registered installer to look at it, not every plumber or gas fitter is qualified to look at these type of cylinders it is a separate qualification from plumbing and gas, ask for their id so you don't get a Muppet in!

 

[picasso]

answer to dan yes I am registered, question for you what makes you think the pump is in the wrong place ? looks fine to me I wrote to close the valves (and possibly find the cause of the problem)until he got the pump changed, I didint suggest he leave it like that.

 

[plumberdan]

Because its on the cold feed causing hot and cold water to mix at the right temperature bacteria will grow rapidly, if there's is to be secondary circulation pump installed due to system design then a tapping specifically for that purpose should be provided on the cylinder about 3/4 of the way up! You should know this! When the pump is off and you run a hot tap it will draw from the cold mains to cylinder and hot outlet equally mixing the water!

 

[plumberdan]

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• plumberdan
• 22 Aug 2011
• 1

 

[picasso]

Its common practise to tee the secondary return on to the cold inlet, megaflow show this on their instructions and vaillant have the secondary return on the cold water control set just before the inlet to the cylinder, what you see in the picture is a standard setup for cylinders without a secondary tapping.

 

[picasso]

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• plumberdan
• 22 Aug 2011
• 1

ok thats one way of doing it, what you gonna do if the cylinder hasnt got a tapping ?

 

[plumberdan]

Then you have a small cylinder and generally speaking wouldn't need a secondary return, but okay it is possible to do it that way provided as you said a check valve and bronze pump is installed but this is not a preferred method, because you are drawing off hot water and when it returns to the cylinder it will have cooled slightly then the cooler water at the base of the cylinder will cool it again eventually cooling the cylinder and circulating cold water, unless the heat source is constant while the pump runs, which is in-efficient!

 

[sterennie]

So the pump is definately incorrect in this setup? What I mean is, there is no chance whatsoever that it is part of our central heating system somehow? I just want to make sure before I shut of the valves as suggested.

And when you say the valves, I take it you mean the small brass bits immediately above and below the pump here:

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• sterennie
• 23 Aug 2011
• 1

Do I need a special tool to turn these off? And if I do turn them off am I able to just leave them like that long term if I dont want to use a pump?

I didnt really follow the leginnaires bit. Did you mean there is a risk of it with how it is currently setup, or there is a risk of it if I shut of the valves either side of the pump?

 

[picasso]

Shutting off the valves can only be short term, you need to change the pump for a bronze one as you will have standing water in the return pipe, the pump is definately the wrong one as its only suitable for heating systems and will rust with the fresh water flowing through it, you dont need special tools a small spanner will do, the valves you have pointed out are the right ones to shut off, I am not sure about the legionaires bit as the water is going back into the cylinder to be reheated, maybe dan can explain.

 

[sterennie]

Ok great, I will give it a go tonight at shutting off the valves to see if that has any effect on the hot water supply throughout the flat. Just to be clear though, I just use a spanner to tighten up the valves right? which basically closes them and stops the flow of water through them?

I have previously googled the terrier tc6 and im sure it said it could be used for both central heating and hot water circulation, so is it just a case of being a cheap pump?

 

[Gasguru]

What you read about the Terrier pump refers to domestic hot water on the Primary side ie. it's use with a boiler circulating heating water.

The pump is NOT suitable for domestic tap water.

The water regs recommend that the domestic water is stored at a minimum of 60c to prevent Legionella and it is also distributed at not less than 50c for the same reason. There is also a recommendation regarding maximum pipe lenght from the cylinder to outlets in order to conserve water/energy. These requirements can be met by insulating the pipe and perhaps the addition of a circulator to keep the "dead leg" pipework water at a sufficiently high temperature to meet the requirements. The water regulations do not go into any detail but it is also common to have the circulator controlled by a timeclock to conserve energy/prolong its life.

Use a spanner to tighten the gate valve (above or below) the pump. As has been mentioned the pump is probably corroded and no longer functioning and the non return valve below is no longer operating as it should do. If the water temperature improves then a suitable pump and valve should be installed. the expansion vessel pressure should also be checked.

 

[sterennie]

I just went to shut off these valves but then I realised I wasnt entirely sure which bit of it I need to turn exactly! There is the nut shaped part that looks like it is threaded and is slightly sticking out, then there is also a thinner piece coming out the middle from that and both parts seem to be able to turn. Ive taken another photo of it close up:

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• sterennie
• 23 Aug 2011
• 1

Sorry for the probably stupid question but I want to make sure I dont cause any damage!

 

[Gasguru]

The square bit on the end.

 

[sterennie]

I have closed off the valve below the pump and we now have hot water coming out of all outlets! Massive thanks to everyone who replied! Its a massive relief to have that sorted. Well almost sorted anyway. I guess I now have to get someone in to replace the useless pump?

My question now is, how long can/should I be able to leave that valve closed off? I take it its completely safe as it is now? Do I need to get it sorted as soon as possible or just when it is convenient?

Also, do I have to get another pump in its place if I dont really intend to use it or can I just put more pipe in its place?

 

[Gasguru]

How long is the pipe run from the cylinder to the furthest outlet? That governs whether the pump is required in order to meet the water regs if you choose to abide by them/save water.

To dispense with the pump would require the pipework to be capped at the cylinder inlet end AND the other end of the return pipework...this of course could be under the floor so may not be practical. Again there is another water reg that prohibits branches of pipework containing standing water.

You can leave the valve closed for the time being whilst you arrange for a plumber (with a G3 unvented qualification) to replace the pump (suitable for domestic water) and checkvalve.