Boiler Pressure Problem

Bendy_House

The small mains booster pumps are - I understand - limited to  max of 12 lpm. That is not a lot, and would need sharing between the hot and cold.

Get good advice from your plumbers, so you know what they will be offering you.

plumb1_2

lamialex said:

. Getting some quotes now, seems like we are gonna need a  mains booster pump since pressure in the house is not great.

And that’s probably why you have storage tanks. 

First thing a gas engineer to check the flow and pressure rates before recommending fitting a Combi.
looking at how your boiler is piped up breaks the 3 T rule, vent first, then cold feed, then to heating/ cylinder circuit.
Lack of water in the boiler, most probably when your mate made a hole in the pipe and drained water out of the system. And cold feed might be blocked or air locked.
Attach a hose pipe to a drain off and start draining the system, hopefully it will pull the water through the F&E  tank. 

My advice is get a good plumber or heating engineer to sort it.

Bendy_House

You have a good reason to go combi, Lami, since you'll be losing your loft space at some point. But, with a poor mains supply, and relying on what I presume is a small booster pump (12lpm), I think you will be bitterly disappointed with the performance.

Your quoting plumbers should all be able to tell you (a) your cold mains flow rate in lpm, and (b) the pressure in bar it is being supplied at. Could you let us know these figures, please?

They should also be able to offer options for improving this. For example, if your neighbours have much better rates, then it could be down to a damaged, undersized or partially blocked supply pipe. Or - although it'll need room somewhere, perhaps in a garage? - you can install a mains booster TANK. That WILL sort it.

Ask questions. Get answers. "What will the flow rate be like?", "Is that good enough for us?" "What will showers be like?" Etc.

Another issue is, if the total mains supply is only going to be 12lpm, then what size combi do you fit?! A smallish one? In which case, you'll ALWAYS have a smallish hot performance even if you later add a booster tank, or sort the supply. Or do you future-proof and fit a biggie, when it won't be able to initially perform to it's best?

Essentially, fitting a combi to a poor mains supply is not a good move unless contingencies are planned for.

lamialex

We have just seen two plumbers and one of them recommended :

a Stuart Turner Flomate Mains Booster 3 Bar pump and 100l vessel (100l vessel has the capacity of 50l of water) to improve the pressure in the house.

At the moment it's 7 lpm and we have been told by our neighbours that they also don't have good water pressure, it's because we are on a hill I'm told. I don't know what we are getting at the stop valve, I need to contact the water company.

the other plumber told us we wouldn't need a tank to go with the booster pump, we could have the pump installed where we are getting the water in the house cause it wouldn't affect the neighbours. 
Now I am confused as to why one is telling us we need a tank and the other one no.

still looking into changing our supply pipe, the water company has changed the communication pipe cause we had the lead content checked and it was not good. Pressure was a bit better but not great so we were told changing the supply pipe could improve it but i doubt it would make such a big difference. The pressure when running the hot water is terrible, this is why the previous owners had a shower pump, it's not great in my opinion.

but very good points you had in there and i will definitely ask those questions you mentioned to those two plumbers. thanks

lamialex

First thing a gas engineer to check the flow and pressure rates before recommending fitting a Combi.

so a gas engineer would help us understanding how to get a better pressure before we do any work on the boiler?

Bendy_House

lamialex said:

First thing a gas engineer to check the flow and pressure rates before recommending fitting a Combi.

so a gas engineer would help us understanding how to get a better pressure before we do any work on the boiler?

They should.  But from my experience, not all are clued up about the options...

lamialex

 great... 

Bendy_House

lamialex said:

We have just seen two plumbers and one of them recommended :

a Stuart Turner Flomate Mains Booster 3 Bar pump and 100l vessel (100l vessel has the capacity of 50l of water) to improve the pressure in the house.

At the moment it's 7 lpm and we have been told by our neighbours that they also don't have good water pressure, it's because we are on a hill I'm told. I don't know what we are getting at the stop valve, I need to contact the water company.

the other plumber told us we wouldn't need a tank to go with the booster pump, we could have the pump installed where we are getting the water in the house cause it wouldn't affect the neighbours. 
Now I am confused as to why one is telling us we need a tank and the other one no.

still looking into changing our supply pipe, the water company has changed the communication pipe cause we had the lead content checked and it was not good. Pressure was a bit better but not great so we were told changing the supply pipe could improve it but i doubt it would make such a big difference. The pressure when running the hot water is terrible, this is why the previous owners had a shower pump, it's not great in my opinion.

but very good points you had in there and i will definitely ask those questions you mentioned to those two plumbers. thanks

7lpm flow is complete and utter pants. Clearly unusable with a combi boiler without it being boosted.

A different - and almost equally important - factor is the pressure with which that pitiful flow is being delivered. Although there does tend to be a correlation betwixt the two, they are quite different things. It is quite possible, for example, for there to be a pitiful flow but it being supplied at a decent pressure. If the mains supply pipe to your house was partially crushed, for example, then this would restrict the flow, but the static pressure would remain pretty much as before (tho' it would drop off rapidly as soon as you started to draw water).

Any plumber considering installing a combi or an unvented hot cylinder (eg a Megaflow) should be checking both factors.

Ok, one plumber recommended a ST mains booster tank/pump. The other said a mains booster pump on its own will do.

In a nutshell, the 'pump only' guy will leave you with a painful system. Water Boards restrict the amount of water you can 'pump' from the mains to 12 lpm. 12lpm is still poor. This will give you an 'ok' shower - perhaps fractionally better than a powerful (10.8kW) electric shower, but turn on any other tap in the house or flush the loo, and it'll drop to half that or worse. I really do not think that this is acceptable at all. You would only entertain this if you simply HAD to have a combi AND you didn't have any room in the house for a booster tank. 

The other guy suggested you could fit the 100l ST booster tank. I've looked that baby up, and it'll seemingly supply up to 18lpm (that's pretty good, tho' not 'very') for up to 8 minutes, after which it'll then maintain a min 12lpm flow rate as it'll keep on pumping from the mains. That's more like it. It's for you to work out if 8 mins at 18lpm is enough - time how long showers take, that sort of stuff. For MOST kitchen and bathroom use, it'll be absolutely fine. For filling baths, it'll be painful after the 18lpm rate is used up. They obviously make larger sizes too, but you need the space for them, which could be in the garage, or in a small, purpose-built insulated shed.

As always, the BEST solution to a poor mains supply is to upgrade the supply pipe from the street to your house IF this will do the trick, but it would appear as tho' this might only have limited results in your case - but I don't know.

A similar product is made by Challis, and these are interesting becuase if your PRESSURE is good but your FLOW is poor, then they can work without a pump at all; the mains pressure will slowly fill and pressurise the tank, and this will then be delivered as required. I would suggest, tho', that your pressure would need to be in excess of 2 bar before you'd consider a pumpless model. They also do pumped versions, of course, and these fill and pressurise the tank like the S-T ones do.

This shows the principle of these booster tanks: https://www.youtube.com/watch?v=T5er8Tkec8Q

One more thing to consider about these; the pumps will make some noise, so if you can fit it outside the house, that would be better.

lamialex

that video is very good for clueless people like me!!! thanks for the share
and where do you find the time to write all of this and being so helpful with your explanation?
yeah 7lpm is bad, i wanted to cry when i first switched on the shower... 
would be interesting to see what the neighbours get
I am contacting the water company tomorrow so I can know how much pressure at the stop valve and also contact one of the plumbers and ask them more about that water booster.
Good idea about putting the tank in the garage and also good to know it would only give us a high pressure for 8 minutes, maybe we should look into a bigger tank? 
and yes been trying to replace that supply pipe but no plumbers i contacted want to do it!!!! crazy! i knew plumbers were busy but that busy!

Bendy_House

If you do have a garage where you can put that tank, then deffo put it there, and double deffo go larger.

Do some research on the options - ST, Challis, and Grundfos are the biggies.

Bro had supply issues in his 6th floor flat and some plumbers were coming up with some daft solutions that even I knew wouldn't work. Most just weren't aware of these booster tanks either. After some research, I was personally keen on the Challis, and got good info straight from the boss (I think, Mr Challis ..), but the good plumber we ultimately used was "I only fit Grundfos...", so that's what bro got.
It certainly works - very impressive. But, the Grund is different from the Challis in that it doesn't have a pressurised tank, but instead one that fills slowly from the mains and the contents are THEN pumped to the house. Two issues with this design: one, the pump fires up every time you open a tap, and this can be heard as it's on the roof, and two, it refills slowly as the mains is worse than yours, and t'other day it ran dry! The Challis (and, I think, the ST) wouldn't have done as it pumps FROM the mains, and not TO the house.
Now it looks as tho' bro will have to add ANOTHER wee pump, a wee mains booster just to FILL the Grund! Sheesh...
The Challis seems to me to be ideal in operation, but I think the ST is similar.
Anyhoo, these WILL sort your supply issue, no question.
I'd do some research to compare them - get some facts, figures and prices for each.