Luke Warm Water from Hot Tap

[tyzer007]

Hello - and thank you in advance for your help on this one.

We have a Salamander Homeboost pump fitted to the mains supply to our flat. We have tanked hot water which is heated by our Valliant Ecosystem 30KW boiler. The flat has 3 bathrooms upstairs, 1 downstairs and kitchen taps.

When the Homeboost pump is on, we check the temp coming from the tank (37C) and when we disconnect the hot tap from the kitchen mixer tap and check the temp it is 16C. The same is true for one of the upstairs bathrooms. The problem seems worse for the bathtub where there are dedicated hot and cold taps compared to the mixer tap for the shower.

When the pump is not turned on, the temperature in the kitchen and affected bathroom is Ok - but not as good as the hot temperature from the other 3 bathrooms.

We think that the issue may be a mixer tap that is allowing the hot and cold to intermingle. But we don't know how to trace this to identify for sure.

According to Thames Water we are in a Pressure Managed area which means our water pressure is fine daytime, but that in the evening Thames drops the pressure and then we need a boost.

Any help is diagnosing this problem is much appreciated. Thank you!

 

[Riley]

WhT sort of hot cylinder have you got. Any pics

 

[Burger]

Have you changed any of the taps recently? Had any work/modifications done recently?

 

[tyzer007]

WhT sort of hot cylinder have you got. Any pics

MegaFlow - CL210

We know that there is a flow balance valve attached. We initially thought it had failed so have replaced that - but with no change.

thank you!

 

[tyzer007]

Have you changed any of the taps recently? Had any work/modifications done recently?

We have had a new boiler installed (plumber who did the install came back - but was unable to diagnose the issue). We changed one of the upstairs shower mixer taps - professionally changed.

 

[Riley]

Unlikely to be related but no one in their right mind should’ve fitted a megaflow to 12litres a minute pumped incoming.

 

[Riley]

The only way to test is to isolate the cold on each mixer and see if it affects your problem

 

[tyzer007]

Unlikely to be related but no one in their right mind should’ve fitted a megaflow to 12litres a minute pumped incoming.

Thanks for this. Can you explain a bit more? We attached the HomeBoost pump to the mains so that there would be the same pressure going to both hot and cold.

 

[tyzer007]

The only way to test is to isolate the cold on each mixer and see if it affects your problem

Due to the nature of the fittings it is not possible to isolate. (Builder was not the best - always cutting corners.)

There are isolating valves in the kitchen - but nowhere else. Not even in the bathroom sinks. And due to the nature of the shower mixer valves, we can remove the cartridges - but can't actually shut them off.

I guess my question is: "Do you think the most likely situation is that one of the mixer valves is the culprit?" - Because if that is the case I think I can identify which one based on the way the pipes flow.

In other words - The cold and hot have already mixed by the time they get to the kitchen and there are only 2 taps between the tank and the kitchen.

Again - many thanks.

 

[Riley]

Thanks for this. Can you explain a bit more? We attached the HomeBoost pump to the mains so that there would be the same pressure going to both hot and cold.

The Homeboost pump would give you a maximum of 12lpm as water regs prevent them giving you more. On that basis I would never in a million years be fitting an unvented cylinder as the flow rate is not sufficient.

 

[Riley]

Due to the nature of the fittings it is not possible to isolate. (Builder was not the best - always cutting corners.)

There are isolating valves in the kitchen - but nowhere else. Not even in the bathroom sinks. And due to the nature of the shower mixer valves, we can remove the cartridges - but can't actually shut them off.

I guess my question is: "Do you think the most likely situation is that one of the mixer valves is the culprit?" - Because if that is the case I think I can identify which one based on the way the pipes flow.

In other words - The cold and hot have already mixed by the time they get to the kitchen and there are only 2 taps between the tank and the kitchen.

Again - many thanks.

I really hope I’ve misunderstood but you are saying your hot and cold mix before they reach the kitchen?? Hopefully that is via a tmv and not appalling piping??

The only way you are going to know for sure is to fit iso valves. I wouldn’t want to be changing taps on guess work

 

[tyzer007]

Below are photos of the shower mixer valve - with cover removed.

When we put a hand on the mixer with cover removed and turn on the sink tap we can feel (what we think is) water flowing through the mixer. I am guessing that there shouldn't be any water flowing through the mixer when the shower is off. - right?

 

[tyzer007]

I really hope I’ve misunderstood but you are saying your hot and cold mix before they reach the kitchen?? Hopefully that is via a tmv and not appalling piping??

The only way you are going to know for sure is to fit iso valves. I wouldn’t want to be changing taps on guess work

Sadly - you have NOT misunderstood

We took the sink and isolated the cold and just had the hot open. The temperature of the water leaving the boiler was 37C - by the time it got to the kitchen tap it was 16C - The only way that could happen was if there was mixing somewhere along the way.

Appalling piping? With this builder it's possible! (but I don't think so)

 

[Riley]

I think my friend you need to enlist a plumber. Builders build plumbers plumb

 

[SimonG]

A passing or missing check valve.

All sounds a bit heath Robinson.

 

[tyzer007]

I think my friend you need to enlist a plumber. Builders build plumbers plumb

LOL - Understood
What I meant was, "The builder" as in the company who employed builders and plumbers... most of which were underpaid...

 

[Stu-B]

Get them back if it’s not right

 

[Riley]

Sadly - you have NOT misunderstood

We took the sink and isolated the cold and just had the hot open. The temperature of the water leaving the boiler was 37C - by the time it got to the kitchen tap it was 16C - The only way that could happen was if there was mixing somewhere along the way.

Appalling piping? With this builder it's possible! (but I don't think so)

This is all sounding wrong. Your water isn’t heated in the boiler it’s being heated in the cylinder??

 

[tyzer007]

This is all sounding wrong. Your water isn’t heated in the boiler it’s being heated in the cylinder??

The water is heated through the boiler (plus we have an immersion heater)

My message above was not accurate. What I meant to say was that the water leaving the tank (after being heated via the boiler) is 37C. When I check just the hot supply (isolate the cold) at the kitchen sink it’s at 16C making me think that the cold has mixed with the hot before it gets to the kitchen.

Sorry for my sloppy message

 

[moonlight]

Has someone checked the non return in the shower? back flow issue

 

[Riley]

The water should be leaving the hot water cylinder at a higher temp than 37°c your system has either not been set up correctly temp wise or you have cold hackfeeding. The only way you are going to diagnose is to isolate micers

 

[tyzer007]

The water should be leaving the hot water cylinder at a higher temp than 37°c your system has either not been set up correctly temp wise or you have cold hackfeeding. The only way you are going to diagnose is to isolate micers

Thank you.

 

[tyzer007]

Has someone checked the non return in the shower? back flow issue

I also believe it to be a backflow issue. Will get someone to check. I assume the non return would be built into the cartridge. Right?

 

[moonlight]

I also believe it to be a backflow issue. Will get someone to check. I assume the non return would be built into the cartridge. Right?

It might be behind the shower valve depending on what shower you have. If you can isolate the shower valve you may have you answer. Unfortunately some of the cheap mixer taps can also create the same problem. If its the shower you may be able to just replace the front section.

 

[tyzer007]

It might be behind the shower valve depending on what shower you have. If you can isolate the shower valve you may have you answer. Unfortunately some of the cheap mixer taps can also create the same problem. If its the shower you may be able to just replace the front section.

Thank you!

 

[moonlight]

Just out of interest what is your cylinder stat set at?

 

[tyzer007]

Just out of interest what is your cylinder stat set at?

I don’t know where to look for that. No obvious controls without removing covers.

 

[moonlight]

Sorry its nothing you will be able to check without removing covers. It will need to be check by someone qualified. How do you know the water leaving the cylinder is 37c?

 

[tyzer007]

Sorry its nothing you will be able to check without removing covers. It will need to be check by someone qualified. How do you know the water leaving the cylinder is 37c?

Heat probe gun (IR) pointed at the pipe ...

 

[moonlight]

If your cylinder is fully heated to 60-65c I am surprised it is only leaving at 37c is that at the top of the cylinder?

 

[tyzer007]

If your cylinder is fully heated to 60-65c I am surprised it is only leaving at 37c is that at the top of the cylinder?

From the top of the cylinder

 

[moonlight]

I think it might be a good idea to get a g3 qualified engineer in to check the controls etc on your cylinder.
I have to leave now but will try and see how you get on later. Good luck.

 

[tyzer007]

I think it might be a good idea to get a g3 qualified engineer in to check the controls etc on your cylinder.
I have to leave now but will try and see how you get on later. Good luck.

Really appreciate all the help

 

[tyzer007]

Thank you to everyone who has added great help.

Last night I checked and there is no external thermostat on the megaflow tank. There is a thermostat for the immersion heater set to 4.

The Valliant EcoTec boiler has a flow temp set at 74C. On the front panel there is no symbol for “tap heat” only the boiler symbol.

This makes me wonder how the tank temp is regulated. Any ideas? And yes, this still doesn’t solve the problem of potential backflow in the piping...

Thanks again

 

[Riley]

There absolutely will be a thermostat on the cylinder. The boiler you have is likely what is known as a heat only boiler. This means that it will receive a call to heat water in the central heating or water inside a coil within your cylinder or both. This will be controlled by valves allowing the water to circulate through the radiators or through the coil in the cylinder. It will also be controlled by thermostats which will tell the boiler to turn on and off

 

[moonlight]

Have you not had the shower checked yet?
The thermostat will be on the cylinder, but not something you should be touching. You may also have a faulty valve on the cylinder but again something you are not qualified to look at, so please call in a qualified person to check these problems for you.

 

[Sondstrom]

The water is heated through the boiler (plus we have an immersion heater)

My message above was not accurate. What I meant to say was that the water leaving the tank (after being heated via the boiler) is 37C. When I check just the hot supply (isolate the cold) at the kitchen sink it’s at 16C making me think that the cold has mixed with the hot before it gets to the kitchen.

Sorry for my sloppy message

What’s the circulation temperature of the pipework from the boiler to the cylinder coil? It sounds like the first issue to sort out is why your hot water is only body temperature in the cylinder. I’d want to get the cylinder temperature to 65° or more before messing around with pipework, taps, valves & showers. It’s also worth checking your temperature equipment. 37° is body temperature: does the hot water from the top of the cylinder feel about the same temperature as your hand? It might seem like a daft thing to check but that temperature from the cylinder is surprisingly low.

 

[tyzer007]

What’s the circulation temperature of the pipework from the boiler to the cylinder coil? It sounds like the first issue to sort out is why your hot water is only body temperature in the cylinder. I’d want to get the cylinder temperature to 65° or more before messing around with pipework, taps, valves & showers. It’s also worth checking your temperature equipment. 37° is body temperature: does the hot water from the top of the cylinder feel about the same temperature as your hand? It might seem like a daft thing to check but that temperature from the cylinder is surprisingly low.

Thanks for this. The temperature of the pipes coming into the tank is approximately 65C. The boiler is set to 74C (so the actual water temp to the tank's heat exchanger seems right.) - I spoke to Megaflow and they suggested that it was either a thermostat issue or corrosion/blockage for the heat exchanger coils within the tank.

By turning on the immersion heater we got the water from the top of the tank up to 65C - so now the water coming out is absolutely hot!

 

[Riley]

Is your boiler and cylinder miles apart

 

[Sondstrom]

Is there much difference in the temperature of the flow into the cylinder and the return from it? It’s best tested from cold and the pipework should be notably cooler from the cylinder when it first kicks up and the difference in temperature will decrease as the cylinder gets hotter. If there’s not much difference then try putting some sludge remover in the heating system to give it a bit of a clean but be sure to then drain down completely and refill with inhibitor. You could even disconnect it completely and see what the coil in the cylinder looks like from the pipework connection to it.
An easy check on the thermostat is to test the continuity across the switch and turn it up and down and try to gauge whether it clicks at the right sort of temperature. If you’ve not had the immersion on and the tank is about 35° then you should hear the switch click at around that temperature on the dial.

 

[Sondstrom]

NB. Only do the continuity test on the thermostat if you know what you’re doing and make sure all of the relevant electrics is turned off.